A glance on all course of plant pathology

 

INTRODUCTION IMPORTANCE OF PLANT DISEASE, SCOPE AND OBJECTIVE OF PLANT PATHOLOGY

Science of Phytopathology or Plant Pathology and Its Importance

·      Plant protection has been accepted as broad area of research and technology at the national level by the Indian Council Agricultural Research, New Delhi; and Plant Pathology is an important discipline of Plant Protection.

Plant Pathology- Definition

·      Plant Pathology, also known as Phytopathology is a branch of agricultural, biological or botanical science which deals with the study of diseases in plants - their causes, etiology, epidemiology, resulting losses and management.

Importance of Plant Diseases in plant pathology

·      The crop loss due to diseases is estimated to be approximately 30-50%.

·      Cultivated plants are often more susceptible to diseases than are their wild relatives.

·      Important environmental factors that may affect development of plant diseases are temperature, relative humidity, soil moisture, soil pH, soil type, and soil fertility.

·      Each pathogen has an optimum temperature for growth. High soil-moisture levels favours development of destructive water mold fungi, such as species o Aphanomyces, Pythium, and Phytophthora.

·      High humidity favors development of the great majority of leaf and fruit diseases caused by fungi and bacteria.

·      Soil pH, a measure of acidity or alkalinity, markedly influences a few diseases, such as common scab of potato and club root (Plasmodiophora brassicae) of crucifers.

 

Important epidemics (Sudden out breaks) in plant pathology

Year	Diseases	Causal organism	Origin/ Location	Huge number of population losses due to starvation, economic imbalance, loss of work and migration to other place will happen due to sever epidemics
1845-46	Late bight of potato	Phytophthora infestanas	Ireland
1845-50	Grapes powdery mildew	Erysiphe necator	Europe
1870	Coffee rust	Hemileia vastatrix	Sri Lanaka
1878	Grapes downy mildew	Plasmopara viticola	France
1916-17	Wheat stem rust	Puccinia graminis f.sp.  tritici	USA
1942-43	Brown leaf spot of rice	Helminthosporium oryzae	India
1946-47	Wheat stem rust	Puccinia graminis f.sp. tritici	India (MP)
1970	Southern corn leaf blight	Bipolaris maydis	USA

 

Effect on Society

·      Infected grains or the fruits may contain toxins (such as aflatoxin, fumonosin) which cause insanity, paralysis, stomach disorder and liver cancer.

·      The money spent on the management of plant diseases is also a loss because in the absence of diseases this money could be saved.

·      There are many other implications on the transport and agro-based industry in the event of plant disease inflicted yield loss.

·      There is restriction on the movements of food grains and other agricultural produce due to the threat of quarantine pathogens and pesticide residues in the produce causing further loss.

Objectives of Plant Pathology

·      To study living, non-living and environmental causes of diseases or disorders of the plants.

·      To study the mechanism of plant disease development.

·      To study interaction between host/susceptible and the pathogens.

·      To develop systems of management of plant diseases and reducing losses caused by them.

Scope of plant pathology

·      Scope and responsibilities of plant pathology is unlimited. Its ultimate goal I to prevent and control plant diseases of economic importance. Responsibilities of the science of plantpathology may be summarized as under.

1.   Study of etiology, symptoms, predisposing factors and recurrence of such diseases.

2.   Plant pathology deals with different aspects of plant diseases and has wide scope than human pathology which only deals with only one aspecti.e. plant health.

3.   The branch focuses on understanding how hosts, pathogens, and environments interact to cause plant diseases and on understanding how to control plant diseases.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

HISTORY OF PLANT PATHOLOGY

FATHERS IN PLANT PATHOLOGY

Field	Scientist name	Period
Father of Plant Pathology	Anton De Bary	1831- 1888
Father of Bacteriology	Antony van Leeuwenhoek	1632 - 1723
Father of Phytobacteriology	E.F. Smith	1854- 1927
Father of Virology	M.J. Beijernink	1852-1931
Father of Mycology	P.A. Michali	1679 - 1739
Father of Forest Pathology	Robert Harting	1839-1901
Father of Tropical Plant Pathology	H.M. Ward	1854-1906
Father of Epidemiology	J.E. Vander Plank
Father of Modern Bacteriology	Luies Pasteur	1822-1895
Father of Modern Nematology	N.A.Cobb	1859-1932
Father of Modern Bacteriological Technique	Robert Koch	1843-1910
Father of Botany	Theophrastus	371-287 BC
Father of Indian Phytopathology	E.J. Butler	1874-1932
Father of Indian Phytobacteriology	M.K. Patel

 

DISCOVERED BY

1.   Bactria - Antony van Leeuwenhoek (1676)

2.   Mycorrhiza - Albert Bernhard Frank (1885)

3.   MLO/ Phytoplasma - Doi et al. (1967)

4.   Plant Pathogenic Nematode - John Needham (1743)

5.   Satellite Virus - Kassanis (1968)

6.   Spiroplasma - Davis et al. (1972)

7.   Virus - MW Beijernink (1898)

Note –       ·         Study of fungi is called – Mycology or fungology       ·         Study of plant bacteria is called – Plant bacteriology or phytobacteriology       ·         Study of plant virus is called – Plant virology       ·         Study of plant nematodes is called – Plant nematology       ·         Study of plant disease epidemics – Epidemiology

 

 

 

 

Detailed history

 

1676 -Antonvon leeuwenhoek (Dutch 1632-1729)-

·      Developed the 1^st microscope (some books mentioned the years  1675,1676,1679)

·      1^st publications on Bacteria (1683)

1729 -Pier Antonio Micheli (Italy)-

·      “Founder and Father of mycology”

·      He wrote a book “ Nova Plantarum genera” in 1729

·      Proved that disease is caused by spores

1755 - Matheiu Du Tillet (france)-

·      Considered as “Great grandfather of Phytopathology”

·      Proved bunt of wheat is contagious (external transmission)

1761-1836 - C. H. Persoon (France)-

·      “Founding father of systemic mycology”,

·      Published “Synopsis methodica fungorum” (1801)

1807 - Benedict Prevost (France)-

·      Experimentally proved role of micro-organism in causation of the diseases (Life cycle of bunt fungus)

·      Demonstrated the control of what smut spores germination by steeping seeds in a copper sulphate solution

E.M. Fries (Sweden) -

·      Linneaus of mycology, Father of systemic mycology

·      Wrote a book called “Systema mycologicum” in 1821 (starting point in nomenclature of fungi)

1803-1889 - M. J. Berkeley (England)-

·      Coined the term “ Mycology”

·      Founder of British mycology      

1858- J. G. Kuhn (Germany)-

·      Published 1^st text book in plant pathology “ The diseases of cultivated crops, their causes and their control” in 1858

1831-1888 - Heinrich Anton De Bary (Germany):-

·      Largely Considered  as “ Father of Plant pathology”, “Father of Modern Plant Pathology” and “Father and founder of modern Experimental Plant Pathology”

·      He wrote a book

“Comparative Morphology and the Biology of Fungi, Myceteoza and bacteria” (1866)

·      Introduced the terms ”Haustoria / Sinkers”, ”Symbiosis”, ”Teletospores”, “Myceteoza”, Autoecious and Heteroecious rust, and “Chlamydospores”

·      His students are M. S. Woronin (Russia), O. Brefels (Germany), A. Millardet (France),    H. M. Ward (England), W. G. Farlow (USA) and Fisher (Switzerland)

·      Discoverd the life cycle of Phytophthora infestans (late blight of potato) that causes Iirish famine.

1839-1901- Robert Hartig-

·      Father of “Forest plant pathology”

·      Published  book “Important diseases of forest trees” in 1874

                              “Diseases of trees” in 1882

1880 H. M. Ward (England) - 

·      “Father of tropical plant pathology”

·      Emphasises the Role of environment on epidemiology of coffee rust gave the briding host theory in 1903

·      Recognised necrotic active defence in Bromus, later known as hypersentive response

1882-1885 PMA Millardet (France)-

·      Discovered “Bordeaux mixture” for the control of downy mildew of grapes

·      This discovery is considered as serendicity discovery (accidental discovery)

·      Bordeaux mixture Composition 1:1:100 (1gm of copper sulphate, 1gm of hydrated  lime, 100lit water)

·      The original formula developed by Millardet  contains 5 lbs of CuSO₄ + 5 lbs of lime 50 gallons of water.

·      The chemistry of Bordeaux  mixture is complex and the suggested reaction is:

 CuSO₄ + Ca (OH) ₂ = Cu(OH) ₂ + CaSO₄

·      “Bordeaux” (founded in June 7,1441 ) is the university name in France.

1845-1920 – Pier Andrea Saccardo (Italy) –

·      His famous book is “ Syllome fungorum ” (26 volumes)

1886- 1971- J. F .Dastur –

·      First Indian plant pathologist, internationally known for the establishment of genus Phytophthora and diseases caused by castor (Phytophthora parasitica) and potato

·      1^st president of the “Indian Phytopathological Society” (IPS) in 1948.

·      Reported the 1^st plant viral diseases in India (Sugarcane mosaic virus)

 

1874- 1943 – Edwin John Butler (Ireland)-

·      1^st Imperical Mycologist in India

·      Considered as ‘ Father of modern plant pathology in India”, “ Father of Indian mycology”

·      His book was “ Fungi and disease in plants” in 1918

 

1928 – Alexander Fleming (United Kingdom) –

·      Isolated Penicillin from Pencillium notatum

·      Shared noble prize in Physiology and medicine along with Ernst B. Chain & Howard Walter Florey in 1945

               When I woke up just after dawn on September 28, 1928, I certainly didn't plan to

               revolutionise all medicine by discovering the world's first antibiotic, or bacteria

               killer. But I suppose that was exactly what I did.

                                                                                                            — Alexander Fleming

1940 – K. O.  Muller and H. Borger –

·      Coined the term “Phytoalexins”( antimicrobial compounds in plants)

·      The 1^st phytoalexin is “Pisatin ”(produced from Pea plant), The molecular formula is C₁₇H₁₄O₆

1946 -  H H Flor –

·      Gave gene for gene hypothesis of plant-pathogen genetic interaction whilst working on rust (Melampsora lini) of flax (Linum usitatissimum)

·       He proposed the term "Avirulence gene"(Avr)

·      ( Gene for gene hypothesis :- One is a plant gene called the resistance (R) gene. The other is a parasite gene called the avirulence (Avr) gene. Plants producing a specific R gene are resistant towards a pathogen that produces the corresponding Avr gene product.

1947 – B. B. Mundukur –

·      Started  Indian Phytopathological Soeiety (IPS)

·      Worked on cotton wilt in Bombay state, published Ustilaginales in india

·      First  issue of the journal “ Indian phytopathology” in 1948

·      Published a text book “ Fungi and plant diseases “ in 1949, which was a second book of plant pathology after Butller

1952 – G. Pontecorvo and JA Roper -

·      Discovered parasexuality in Aspergillus nidulans

(parasexuality : - plasmogamy, karyogamy and meiosis not occurs in a regular stage )

·      J A Roper reported the hormonal control of sexuality in fungi

1952. Kittleson – introduced the Capton( kittleson killer) as a fungicide

1963 – J. E. Vander Plank –

·      Considered as “Father of Epidemiology”

·      Published “Plant Disease Epidemics and Control ” in 1963

 

                                       

1964 – Norman E. Borlaug (USA) –

·      Developed semi-dwarf, high-yield stem rust resistant wheat varieties

·      He was often called “ The father of the Green Revolution”

·      He was awarded the Noble Peace Prize in 1970 in recognition of his contributions to world peace through increasing food supply

·      He worked in the fields of Agronomy, Plant pathology and Genetics ( Ph.D. in plant pathology and genetics)

 

HISTORY OF BACTERIOLOGY

Ehrenberg (1829) – Coined the term “Bacteria”

1675 – Leeuwenhoek –

·      Developed 1^st microscope, Considered as ‘Father of Bacteriology’

·      Developed hundereds of microscopes and obtain a magnification of 50-300 diameters.

·      Also discovered the Spermatozoa and the red blood cells

·      1^st publication in bacteria was in 1683

             (Dear god what marvels they are so small a creature – Leeuwenhoek)

1858 – Louis Pasteur (France) –

·      Father of “modern bacteriology” and “Founder of Microbiology”

·      Formulated germ theory of diseases and demolished the spontaneous generation theory

·      Developed the principles of vaccination, microbial fermentation and pasteurization.

·      Created the first vaccines for Rabies and Anthrax

·      Book “memoir on the organized bodies which exist on the planet”

·      (Pasteurization:- Heat-treatment process that destroys pathogenic microorganisms in certain foods and beverages.

Pasteurization of milk of about 62.8° C (145.04° F) for 30 minutes

1876 -Louis Pasteur and Robert Koch -They proved that anthrax disease of cattle was

              caused by specific bacterium.

1876 -Robert Koch (Germany)

·      Described the theory called "Koch's postulates."(out of 4 , 3 was given by Robert Koch 4^th was given by E. F. Smith)

·      He established the principles of pure culture technique.

·      “Father of Modern Bacteriological Techniques”, “Father of Microbial Techniques” “Founder of Modern Bacteriology”.

·      Identified the specific causative agents of tuberculosis, cholera, and anthrax

1878 - T. J. Burill (America) –

·      First time proved that fire blight of apple and pear was caused by a bacterium (now known as Erwinia amylovora) in 1878.

·      Initially the was called  Mycrococcus amylovorus (today known as Erwinia amylovora)

·      He is the “Founder of Phytobacteriology”.

1884 – Christian Gram-

·      Developed bacterial staining technique

·      Based on staining bacteria can be divided into gram positive(+ve)  and gram negative (-ve)

1901-1920 - E. F. Smith (U.S.A)

·      He is also called as "Father of Phytobacteriology".

·      Wrote the 1^st text book on bacterial diseases “Introduction to Bacterial Diseases of plants” in 1920.

F. W. Twort (1915), F. D’ Herelle (1917) – Discovered Bacteriophage individually.

1928 – Alexander Fleming (United Kingdom) –

·      Isolated Penicillin from Pencillium notatum

·      Shared noble prize for the chemotherapeutic use of penicillin in Physiology and medicine along with Ernst B. Chain & Howard Walter Florey in 1945

·      Fleming published his findings in the British Journal of Experimental Pathology in June 1929

1931- Knoll and Ruska- Invented the electron microscope

Selman A. Waksman –

·      Considered as “Father of soil microbiology” and “Father of antibiotics”

·      Discovered the antibiotic ‘Streptomycin’ (Streptomyces griseus)

·      Awarded Noble Prize in Physiology of Medicine in 1952 ( for the discovery of streptomycin)

1948 – M. K. Patel –

·      Considered as “ Father of Indian Plant bacteriology”

·      Started the school of Plant Bacteriology at college of Agriculture (Pune)

·      Found out “Patel agar”( medium for isolating and culturing of Crown gall bacterium) also worked on crown gall bacterium

·      Identified a new species of plant pathogenic bacterium from India in 1948, namely Xanthomonas campestris pv. uppalii

1967 - Y. Doi et al –

·      Discovery of Mycoplasma like organisms (in mulberry dwarf disease

·      The organisms were renamed as Phytoplasma in 1994, at the 10th Congress of the International Organization for Mycoplasmology.

1972 – Davis et al – First observed Spiroplasma (in corn stunt diseases)

 

 

 

HISTORY OF VIROLOGY

Ø Virus :-

·      Plant viruses are sub-microscopic, infectious, obligate intracellular parasites, which do not replicate without a living host.

Ø Virus is derived from Latin word which means - Poison/ Venom/Slimy liquid

Ø Study of Plant viruses and virus like pathogens is called – Plant Virology

    HISTORY:-

Ø  1886 – Adolf Mayer (Germany)-

·      Coined the term ‘Mosaic’

·      He thought that the causal agent was the bacteria.

·      He called sap transmission of tobacco disease is ‘Mosaikkrankheit’

·      Later he performed experiments with Chamber land filter paper, even though the virus retains infectivity.

Ø  1892 – D. Ivanovsky  (Russia) –

·      Proved that the causal agent of tobacco mosaic disease could pass through bacteria proof filters.

·      Concluded that the causal agent of tobacco mosaic (virus) is smaller than bacteria.

Ø  1898 – Beijerinck –

·      Founder and Father of Virology / Father of Environmental Ecology

·      Performed agar diffusion experiments and coined the term ‘Virus’

·      He called the liquid material of virus is “Contagium vivum fluidum” which cause the repeated infection in Tobacco mosaic virus

Ø  1915 – Twort, 1917 -F. D. Herelle – Individually discovered bacteriophages

Ø  1929 – Mckinney –

·      Developed cross protection/ pre-immunization technique for control of citrus tristeza virus (CTV)

·      Cross protection was 1^st used against TMV

Ø  1935 – W. M. Stanley –

·      American biochemist, virologist

·      Done Purification/ Crystallisation of virus (by using ammonium sulphate)

·      He received Nobel Prize in 1946 (for crystallisation of virus)

·      He believed that virus was an autocatalytic protein that could multiply with in the living cell

·      Molecular plant pathology work can be initiated with W. M. Stanley

Ø  1936 – F. E. Bawden and N. W. Pirie –

·      Demonstrated that virus is a nucleoprotein which consists both nucleic acid and protein

Ø  1939 – Kausche et al – Saw virus particles (TMV) for the first time with the help of

              electron microscope

Ø  1956 – Gierrer and Schramm –

·      Showed that nucleic acid is the infectious agent

·      Also investigated about double standard RNA viruses (ds RNA)

Ø  1967 – Doi et al – First observed Phytoplasma (In mulberry dwarf disease)

Ø  1971 – Dienner and Raymer – reported 1^st viroid disease potato spindle tuber viroid.

Ø  1972 – Davis et al – First observed the Spiroplasma (in Corn stunt disease)

1976 – Voller et al, 1977 – Clark and Adams – Developed ELISA technique and used ELISA in Plant virus detection.

 

CLASSIFICATION OF PLANT DISEASES

DEFINITIONS AND CONCEPTS

·      Disease: Disease may be defined abnormal deviation or changes in the normal physiological functioning of plants.

·      Disorder: The diseases caused by the deficiency of nutrients or unfavourable environmental are sometimes termed as disorders or physiological disorders.

·      Pathogen: It is the agent responsible for inciting pathos  i.e. ailment or damage.

·      Parasite: These are the organisms which derive the food materials needed for their growth from other living organism (the host). All the pathogens are parasites but all the parasites are not pathogens.

·      Biotrophs are the organisms which regardless of the ease with which they can be cultivated on artificial media obtain their food from living tissues only in nature in which they complete their life cycle). They were earlier also called

·      Obligate parasites – Only live on living hosts/ plants. e.g., rusts, smuts, powdery mildews etc.

·      Saprophytes/saprobes are the organisms which derive their nutrition from the dead organic matter. Some parasites and saprophytes may have the faculty or (ability) to change their mode of nutrition.

·      Facultative saprophytes are ordinarily parasites which can grow and reproduce on dead organic matter under certain circumstances.

Note - A parasite is called necrotroph when it kills the host tissue in advance of penetration and then lives saprophytically, e.g. Sclerotium rolfsii and Pythium species. Similar to necrotrophs are facultative parasites which live as saprophytes but under favourable conditions they can attack living plants and become parasites. The necrotrophs are also known as perthotrophs or perthophytes.

·      Pathogenicity is the ability of a pathogen to cause disease under a given set of environmental conditions. Whereas, pathogenesis is the chain of events that leads to development of a disease in the host.

·      Parasitism is a phenomenon by which a plant parasite becomes intimately associated with the plant; it draws nutrition and multiplies and grows at the expense of the plant host.

·      Virulence is the ability of a pathogen to cause disease. The term aggressiveness is often used to describe the capacity of a pathogen to invade and grow.

 

Classification

1.   Non-infectious diseases (in simple nutrient deficiency disorders)

·      Diseases with which no animate or virus pathogen is associated.

·      Cannot be transmitted.

·      No parasite is associated (Non-parasitic diseases).

·      Ex-  Tip rot or Necrosis of mango - B deficiency.

        Black heart of potato - Oxygen deficiency.

       Khaira disease of paddy - Zn deficiency

2.   Infectious diseases

                     ·         A specific pathogen is responsible for the diseases.

                     ·         diseases are infectious, contagious and transmittable

Koch's postulates are:

The Four Koch postulates

1. The organism must always be present, in every case of the diseases.

2. The organism must be isolated from a host containing the diseases and

    grown in Pure Culture .

3. Samples of the organism taken from pure culture cause the same diseases

     when inoculated into a healthy, susceptible animal in the laboratory

4. The pathogen must be re-isolated and on comparison with original culture it

     must be found to be identical)

Note - 4^th Koch postulate was given by E. F. Smith

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

GENERAL CHRACTERISTICS OF FUNGI

Ø The branch of biology that deals with fungi is called ‘Mycology’

Ø Fungus is a Latin word which means ‘Mushroom’

Ø Fungi (definition)- Fungi is eukaryotic, achlorophylls, spore bearing organisms that can reproduce by both sexual and asexual manner and can obtain nutrients through haustoria

§  Eg – Yeast, mould, rusts, smuts and mushrooms

Morphological characters of fungi

Thallus – Entire body of fungus is called thallus (mass of hyphae constitute to form thallus). Vegetative/ somatic thallus gives rise to reproductive structures, from which spores are produced either sexuall or sexually

·      Holocarpic – whole thallus is converted into one are more reproductive structures

Eg – Synchytrium and Olphidium

·      Eucarpic – only a portion of thallus become reproductive

Eg – Oomycota, Ascomycota and Basidiomycota

Mycelium – filamentous vegetative body of the fungus is called mycelium/ Single thread of hyphae

Hypha - Individual branch of mycelium which are generally uniform in thickness, usually about 2-10 μm in diameter. The hyphae may be septate or aseptate

·      Coenocytic hyphae - The aseptate or non-septate hyphae having the nuclei scattered in the cytoplasm (obscene of septa/ cross walls).

·      Septate hyphae- The hyphae have septa having perforations through which cytoplasmic strands, containing nuclei can migrate from one cell to the other. (presence of septa)

 

 

Doipore septa

·      It is a complex type septa with barrel shaped central pore and hemi spherical cap is called parenthosome/ pore cap

·      Dolipore septum is formed in Agaricomycotina certain basidiomycetes.

 

Plasmodium – Naked,motile multinucleated mass of protoplasm is called plasmodium

Rhizomorphs: Thicker root like aggregates. Also called mycelial cords

Sclerotium: It is a hard and compact vegetative resting structure resistant to unfavourable conditions. It is mostly made up of pseudoparenchymatous cells

Eg – Sclerotium, Rhizoctonia, Sclerotinia, Claviceps

Stroma: some fungi also develop mat like structures which contain the fruiting bodies.

Fungal cell structure

·      Fungal cell wall is made up of Chitin + glucan, whereas

·      Oomycota cell wall is made up of cellulose

·      Zycomycota cell wall is made up of  Chitosan chitin

Special somatic structures

·      Appresorium – It is the anchoring organ/ attachment organ of fungi

·      Haustorium – It is absorbing organ, which absorb nutrients from host.

·      Rhizoid – short root like filamentous outgrowth devoid of nuclei

Eg - Rhizopus

Modifications of fungal hyphae

1.   Plectenchyma: Hyphae are closely packed together, easily indistinguishable from true tissues of higher plants

2.   Rhizomorph: Hyphae is aggregated longitudinally and form long root like strands of compact masses. (Eg) Armillariella mellea.

3.   Sclerotium: Hard, compact resting body, made up of mass of mycelium produced after a vigorous active growth.

Ex. Brown irregular - Rhizoctonia solani, Black irregular – Rhizoctonia bataticola,

4.   Chlamydospore: Swollen or thickened resting structures by the rounding up of cells (resting cells) Ex. Fusarium, Volvariella.

·      Rhizomorph, selerotium and chlamydospores - resting spores of fungi

5.   Gemnae: Thin walled chlamydospre borne terminally. Eg. Mucor sp.

6.   Appressorium: Localized swellings of the tip of germ tube for attachment in the infection.

7.   Haustoria: Lateral outgrowth of intercellular or superficial hyphae which will help to absorb food and nutrients from the host. Eg. Erysiphe

 

TYPES OF PARASITISM

I. Parasite: Obtain food from living source

1.   Ectoparasite - Live on the external surface (eg) Erysiphe polygoni.

2.   Endoparasite - Grow inside the host cell (intracellular) or in between the cell (inter cellular) of the host plant and draw nutrition. (eg) Leveillula taurica.

3.   Facultative parasites - Usually live as saprophyte but can attack living tissue (eg)

Pythium, Rhizoctonia sp.

4.   Facultative saprophyte - Usually live as parasite but can grow saprophytically (eg)

Phytophthora sp. Venturia inaequali, Spacelotheca sp.

5.   Obligate parasite - occur as parasites in nature and cannot be cultured. (eg) Downy mildew, Powdery mildew.

6.   Biotrophs - obligate parasites which are cultured under laboratory condition

7.   Necrotrophs - There are some intermediate parasites which invade and kill host cell (eg) Phytophthora, Claviceps, Venturia.

II. Saprophyte: Obtain food from non-living source

1.   Synergism - ability of two organisms to grow better conjointly than singly (eg) Diplodia natelensis and Colletotrichum gleosporioides on citrus

2.   Symbiosis - Derive nutrition from a host and provide some benefit in return. (eg) VAM.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

REPRODUCTION IN FUNGI

·      Spore – minute, simple and basic reproductive unit of fungus, which are capable of growing into a new thallus. The process of formation of spores are called Sporogenesis/ Sporulation

·      Sporangia – It is a sac like structure in which spores are formed

·      Sporangiphore – sporangia are produced at the end of the of the undifferentiated or on specialized spore bearing structure are called Sporangiphone

 

Reproduction in fungi of two types

1.   Asexual reproduction – It does not involve the union of nuclei or gametes and hence called as somatic or vegetative reproduction 

ü Spores are produced by asexual are production are celled mitospores/ asexualspores

a)   Fission – parent cell divides into two daughter cells by constriction. The nucleus is divided into two halves b formation of transverse septum

Eg – Yeast

b)  Budding – Small outgrowth or bud produced from the parent cell enlarges gradually and nuclei migrates into the growing bud an then bud eventually breaks off to form the new thallus 

c)   Fragmentation – Small fragment of hyphae detached from the parent mycelium to grow into new thallus. These small fragments/spores are called arthrospores/Oidia

Eg– Powdery mildew

d)  Asexual spores

·      Zoospores – Motile asexual spores of Oomycota produced with in zoosporngium. They are always naked (without cell wall)

·      Planospores = motile spores = Swarm spores

·      Aplanospores = non motile spores

·      Chlamydopsores  - Thick walled resting spore formed either single or in chains from terminal or intercalary cells o the hyphae eg – Fusarium, Saprolegnia

·      Gemmae – Chlamydospores dispersed inn water currents is called gemmae

 

Types of flagella in fungi

·      Flagella – Locomotory organ of fungi

·      Axoneme – feather like a central rachis, the hair of flagella is called flimmers hairs/ mastogoneme

Two types of flagella are found.

1. Whiplash - long rigid base with a short flexible end

2. Tinsel - Feather like

Asexual fruiting bodies –

A.  Pycnidium – It is a hallow , flask shaped or globose fruiting bodies with  narrow circular mouth called ostiole. It has a wall made up of multilayer pseudoparenchymatous sterile tissue, called peridium. The inner wall of the fruiting body is lined with numerous short conidia called pycnidiospores

Eg – Macrophomina phaseolina, Diplodia natalensis, Botrydiplodia

        theobromae

B.  Spordachium – It is a hemispherical, barrel shaped compound conidiophore produced by Fusarium, Tubercularia and Epicoccum. It consists of cushion shaped  aggregation of hyphae in the lower part and expresses the conidia on the upper part.

C.  Acervuli – It is a saucer shaped depressed pseudoparenchymatous aggregation of hyphae which develops beneath the surface of the host with a bed of closely packed parallel simple conidiophores

Eg – Colletotrichum, Pestalotia

D.  Synemma – loose aggregation of branched or unbranched erect conidiophore to form dene fascicle, similar to mycelial strands

Eg – Ceratocystis, Graphium

E.  Sori – Spore bearing hyphae eg – Smut sori, Rust sori

 

2.        Sexual reproduction –

       Three typical phases occurs in sequence during sexual reproduction

A.  Plasmogamy - Union of protoplasts bringing their nuclei togeather within the same cell

B.  Karyogamy – Fusion of two nuclei result in the formation of zygote/ diploid nuclei. The organ in which karyogamy takes place is celled Zeugites

C.  Meiosis – Fused diploid nucleus undergoes meiosis, which reduced the number of chromosomes to haploid. The organ in which meiosis takes place is celled Gonotoconts

Types of plasmogamy

                              i.     Planogametic copulation/ Gametogamy

a)   Isogamy/ isogamous fertilization – fusion of isogametes of same size and shape

Eg – Olphidium and Synchytrium

b)  Anisogamy/ anisogamous fertilization - fusion of anisogametes in which gametes are morphologically similar but differ in size

Eg – Allomyces

c)   Heterogamy/ ooplanogametic copultion – fusion of motile male gametes with non-motile female gametes

Eg - Monoblephariales

                            ii.     Gametangial contact/ Gametangiogamy

Fusion of two morphologically distinguishable gametangia with undifferentiated protoplasm and nuclei. The gametes pass either through pore dissolved at the point of contact called Fertilization tube/ trichogyne

                         iii.     Gametangial copulation/ Aplanogametic copulation/ Gametangy

a)   Hologamy – entire content of one gametangium passes into another through pore developed in the gametangial wall at the point of contact

Eg – Yeast

b)  Direct fusion/ isogamous copulation – two morphologically similar gametangia fuse and to become a single cell

Eg - Mucor and Rhizopus

c)   Anisogametangial copulation -  fusion between unequal gametangia

Eg -  Zygorhyncus

                          iv.     Spermatization – some fungi produce numerous, non-motile minute, spherical uninucleate spores are called spermatia, which are produced from the flask like sexual apparatus called spermagonium

                            v.     Somatogamy – no sex organs are produced, but the undifferentiated somatic cells functions as gamtes

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Parasexual reproduction – Plasmogamy, karyogmy and meiosis takes place in sequence but not at specified points in life cycle. The phenomenon of parasexuality was first discovered by Pontecarvo and Roper in 1952 in Aspergillus nidulans.

 

 

Subdivision	Sexual spore	Asexual spore
Mastigomyctina	Oospore	Sporangiospore
Zygomycotina	Zygospore	Aplanospore
Ascomycotina	Ascospore	Conidia
Basidiomycotina	Basidiospore	Conidia
Deuteromycotina		Conidia

 

 

 

TAXONOMIC RULES FOR FUNGI AND FUNGI LIKE ORGANISMS

Taxonomy is a part of biological science which deals with the study of naming and classification of organisms.

Taxonomist	Groupings / classification
Linnaeus (1753)	2 kingdoms
Ernst Haeckel (1866)	3 kingdoms
Herbert Copeland (1956)	4 kingdoms
Whittaker (1969)	5 kingdoms
Carl Woese (1977)	6 kingdoms

Systematics of fungi and fungi like eukaryotes

The nomenclature is the branch of systematics that determines the correct scientific name for taxon. The naming of fungi was previously governed by International Code of Botanical Nomenclature (ICBN)

The rules of writing scientific names

1.   Binomial system – Use two names, generic name and species name.  the genus and species have no fixed endings

2.   Trinomial nomenclature – Add a third name to the binomial to provide further information of the organism (eg – forma specialis, race, pathovar)

3.   Author’s name – Place the name of the taxonomists who were the first person who gave the names to given organism and the end of the binomial, and abbreviate

Guidelines for writing scientific names

·      Capitalize first letter of generic name, while the rest, including whole of species, in a small cases. Leave a single space between genus name and species name. in case where the author’s name is to be included use standard abbreviation for the author name.

·      Use Italics for genus name and species name, but not the author name, in hand written manuscript, or when use a type writer with no Italics, underline that are to be italicized.

·      Name lower the species level are to be treated in the same way as the binomial, i.e. italicized note that the whole subspecies, forma specials, race, variety, etc. which are abbreviated are not italicized

Eg – Fusarium oxysporum f.sp. vasinfectum (G.F.Atk) W.C. Synder & H. N.Hansen

 

 

 

 

Difference between Eukaryotes and prokaryotes

S.no	Eukaryotes	prokaryotes
1	Possess advanced cellular organism	Show primitive cellular organisms
2	Cell wall is made up of cellulose (plants), chitin (fungi)	Cell wall is made up of peptidoglycan (mucopeptides)
3	Membrane bound organelles such as ER, golgi complex, mitochondria, chloroplast and vacuoles are present	Membrane bound organelles such as ER, golgi complex, mitochondria, chloroplast and vacuoles are absent
4	Ribosomes are larger made up of 80S units	Ribosomes are smaller made up of 80S units
5	Genetic material is found in well organised chromosomes	Genetic material is not found in well organised chromosomes
6	DNA is long and liner, histone bound	DNA is shorter and circular, not histone bound
7	Cell divides by mitosis and meiosis	Cell divides by fission
8	9+2 arrangement of flagella	Flagellum is single fibrillar type

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

GENERAL SYMPTOMS OF FUNGAL DISEASES

1. Leaf spots - Localized lesions produced on the leaves consisting of dead and collapsed cells. 

Eg – Brown leaf spot of rice (Bipolaris oryzae)

2. Blight – Browning and death of leaves, floral organs, stems and branches.

Eg - Early blight of tomato (Alternaria solani)

3.      Wilts - Generalized loss of turgidity and drooping of leaves or shoots.

Eg - Quick wilt of pepper (Phytophthora capsici)

4.      Rusts – Infected plants shows small lesions on stems or leaves, usually rusty appearance on the leaves and stems, but can also be black or white.

Eg – Wheat stem rust (Puccinia graminis tritici)

5. Smuts – The grains or seeds are replaced by black colour spore masses
6. Mildews - Leaves, stems, blossoms, and fruits, covered with whitish mycelium and the fructifications of the fungus.

Eg – Downy mildew of grapes – (Plasmopara viticola)

7. Canker - Localized necrotic lesion on woody tissue, often sunken.

Eg - Apple European Canker (Nectria galligena)

8. Dieback - Death of shoots and twigs generally starting at the tip of the infected plant part.

Eg - Die back (Diplodia rosarum)

9. Root rot - Disintegration or decay of plant root system.

Eg – Root rot (M. phaseolina)

10. Scab - These are the localized lesions which are due to the slightly raised and cracked outer layer of the fruits, leaves or tubers etc. the cracked tissue becomes dry and corky.

Eg - Apple Scab (Venturia inaequalis) and Pear Scab (Venturia pirina).

11. Damping off – Rapid death and drying of young seedlings.

Eg – Pythium damping off (Pythium aphanidermatum)

12. Soft and dry root rots – Disintegration and decay of the tissues fleshy leaves, roots, tubers and fruit –

Eg. Phytophthora Root Rot (P. cinnamomi)

13. Anthracnose – Produce Ulcer-like lesion that can be necrotic and sunken. These lesions can appear on the fruit, flowers and stems of the host.

Eg - Beans  anthracnose (Colletotrichum lindemuthianum)

14. Leaf curls - Curling, thickening & distortion of leaves. 

Eg - Peach leaf curl (Taphrina deformans)

15. Decline - Progressive loss of vigour over a period of time. Poor growth, small leaves, brittleness, defoliation, discolouration of leavers and die back.
16. Galls – Enlargement of plant parts and organs, usually caused by excessive multiplication or enlargement of plant cells.

Eg- Club root of Crucifers (Plasmodiophora brassicae).

 

 

          Wheat stem rust                             Corn smut - Ustilago maydis

  

          Powdery mildew                   Root rot                            Leaf spot

         

      Wilt                       Anthracnose (leaf)             Anthracnose (fruit)

   

Damping off                                 Scab                         Die back

 

 

          

                                             Galls or tumours      

                 

 

 

 

 

 

 

 

 

 

 

 

 

LIFE CYCLE OF WHEAT STEM RUST – Puccinia graminis tritici

   Domain – Eukarya

    Kingdom – Fungi

    Phylum – Pucciniomycota

    Sub phylum - Pucciniomycotinia

    Class – Puccniomycetes  

    Order – Pucciniales

    Family – Pucciniaceae

    Genus – Puccinia

                      Species – graminis

 

Stage	spores	Colour	Appearance
O	Pycniospores	Hyaline	Upper
I	Aeciospores	Yellow	Lower
II	Uredospores	Golden brown	Primary host
III	Teliospores	Black	Primary host
IV	Basidiospores	Hyaline	Soil debris

 

Symptoms – Red colour rust pustules appears in stem and leaves. Alternate host is Barberry

Life cycle – When wheat crop attains maturity the uredinia appears on rut pustules and developed as urediniospores, these are single celled, which contains enormous amount of food reserves for long distance dissemination, at the end  of the wheat season it starts to produce less urediniospores and more teiospores.

         Telia are black, elongated, bi-celled, dark brown in colour, it is a resting spore which represents sexual apparatus of the fungus in which karyogamy ad meiosis takes place, when favourable conditions occurs its germinate and produce basidispores of opposite mating types

         Basidiospores infect barberry but not wheat, several basidiospores produce flask shaped pycnium. Several pycnia of opposite mating types are generally formed in the same leaf. On the corresponding to the lower surface it produce aecia

         Aeciospores it contains reserve food material, the aeciopsores can’t germinate on berberry and germinate on wheat leaf.

 

Types of rust –

Ø Autoecious rust – Completes its entire life cycle in a single host

Ø Heteroecious rust  - Requires genetically two hosts to complete their life cycle

Ø Autoecious macrocyclic rust – Eg – B – Bean rust

                                             F – Flax rust

                                             S - Sunflower rust

                                             S - Safflower rust

Ø Autoecious demicyclic rust – Eg – Rubus orange rust – Gymnoconia peckiana

Ø Heteroecious macrocyclic – Eg – Wheat stem rust – Puccinia graminis tritici

                    White pine blister blight – Cronartium rubicola

Ø Heteroecious demicyclic – Eg – Cedar apple rust – Gymnosporangium juniperi  viriginianae

Ø Types of teliospores –

Ø  

Types of teliospore	Example
Single celled  teliospore	Uromyces
Double celled teliospore	Puccinia
Multicelled teliopsore	Phragmidium
Durnip shaped uredospore	Hemileia
Kidney shaped teliospore
Crust like telispore	Melampsora
Parachute like teliospore	Ravenelia

           

 

Life cycle

 

 

 

GENERAL INTRODUCTION TO BACTERIA

Ø The term bacteria was coined by – Ehrenberg

Ø Size of bacteria ranges from – 0.5 to 1.0 µm breadth and 2.0 to 5.0 µm in length

Ø Bacteria belongs to prokaryota (contains a primitive type of nucleus and lacking of well-defined membrane like fungi {except blue green algae}).The bacteria are smaller than fungi and measures about 0.5-1.0 - 2.0-5.0µm

Ø Anton van leeuwenhoek (1676 ) discovered the microbial world with his simple microscope .

‘’Dear god what marvels they are in so small a creature’’  

            Leeuwenhoek

 

 

 

 

 

 

Ø Morphological features of bacteria

Morphologically the bacteria are rod shaped (bacilli), spherical (cocci), spiral (spirilli), coma shaped (vibrios) or thread like (filamentous)

§  Rod shaped bacterium is called  - Bacillus

Bacilli (singular :  Bacillus)

·      Monobacillus – A single rod shaped bacterium

·      Diplobacillus – Rod shaped bacterium arranged in pairs

·      Streptobacillus – A chain of rod shaped bacterium

§  Spherical shaped bacterium called  - Coccus

Cocci (Singlular : Coccus)

·      Monococcus -  A single spherical bacterium

·      Diplococcus -  A pair of spherical bacteria

·      Tetracoccus – A group of four spherical bacteria

·      Streptococcus – A chain of spherical bacteria arranged in a single row

·      Staphylococcus – A group of cocci bacteria forming irregular shapes

·      Sarcina – Cocci arranged in cubes if eight

                  (link - Side share < classification of bacteria< Hima shankar)

·      Bacterial nucleus is called - Genophore (by Ris, 1961) composed of ds DNA

Structure of bacterial cell

                          

i.     Cell wall - The cell walls of bacteria is made of peptidoglycan/ mucopepetide

Differences between gram^+ve and gram^-ve bacteria

Gram+ve	Gram-ve
Teichoic acid present	Teichoic acid absent
Homogenois layer	Three(3)layers
Major portion of cell wall is mucopeptides (85%)	Mucopetides (3-12%)
Protoplast completely digested cell wall	Sphaeroplast
L,P rings are present	L,P,M,S rings are present
while stating it produce violet/purple in colour	while stating it produce pink colour
Ex.bacillus,streptomycin,     Corynebacterium	Most of the bacterium are gram-ve
Much rigid due to the presence of  greater amount of muciopeptides	Less rigid due to the plastic nature of     lipoprotein, lipopolysaccaride

ii.   Pili/ fimbriae -  Fimbriae are hair like structure that are observed as surface appendages on some bacteria where they serve to connect to cells during conjugation (also called sex pili )and allows the DNA to pass from donor to recipient.

iii. Flagella : These are the organs used for locomotion in  motile forms and many times longer than bacteria (4-5 times) than the bacterial cell.

iv. Types of bacterial flagella

1. Atrichous : no flagella are present on the bacterial cell surface

2. Monotrichous : single flagella are present on the bacterial surface

3. Amphitrichous :single flagella are present on the either side of the bacterial surface                       

4. Peritrichous: flagella are present on all over the body

5. Cepalotrichous: turfts of flagella are present on either side of the bacterial surface

6. Lophotrichous: tufts of flagella are present on both the sides

           

v.   Capsule/ slime layer – which protects the bacteria from desiccation

vi. Plasmids: Bacterial plasmid is circular, extra chromosomal double standard DNA present inside the bacteria, which provides additional genetic information to the bacteria

 

 

 

 

 

 

 

 

 

 

 

 

 

REPRODUCTION IN BACTERIA

There are two types of asexual reproduction observed in bacteria

1.   Asexual reproduction

2.   Sexual reproduction

1. Asexual reproduction

i.     Binary fission

·      Cell divided into similar daughter cells by forming a constriction and cellular material (genetic material) is equally shared.

·      A cross wall is formed between the separating daughter chromosomes.

·      This process will take 20-30 minutes

ii.   Budding - A small protuberance or bud developed at one end of the cell

iii. Fragmentation - The multicellular organism break up into small pieces upon maturation

iv. Endospore

·      Produced mostly by Bacillus and Closteridium singly

·      Dormant cell, resistant to desiccation, staining, disinfecting chemicals, radiation and heat.

·      All endospores contain large amount of dipicolinic acid (DPA)

2. Sexual reproduction

i.     Conjucation

·      This was discovered by Lederberg and Tatum in 1946 on Escherichia coli.

·      In this process, two cells come in contact among which one is called as donor and the otherone is receptor cell.

·      Minute portion of donor DNA can pass through the sex pilus into the recipient cell.

ii.   Transformation

·      In 1928 Frederik Griffith, while working with the bacterium Pneumococcus pneumonia (then called diplococcus) the causal organism of pneumonia.

·      One bacterial cell absorbs the genetic material secreted (or) liberated by the rupture of cell wall of another bacterial cell.

iii. Transduction

·      Lederberg and his student Zinder in 1952 discovered transduction in Salmonella tymphimurium

·      DNA from one cell is transferred into another by a virus (bacteriophage)

Genetic mechanism	Organism	Scientist discovered	Year
Conjugation	E. coli	Lederberg and Tatum	1946
Transformation	Pneumonia	Griffith	1928
Transduction	Salmonella	Lederberg and Zinder berg	1952

 

Bacteriophage: A virus which infects the bacterium is called bacteriophage. Bacterophage grows within a cell. That infects the bacterial cell bursts and bacteriophages particle are liberated.

 

Asexual reproduction

 

                  Binary fission                               Budding

   

Fragmentation                        Endospores

Sexual reproduction

 

Conjugation                                          Transformation

 

 

 

SYMPTOMS PRODUCED BY PLANT PATHOGENIC BACTERIA

Plant pathogenic bacteria are basically facultative saprophytes and they enter into the host

plant mostly through wounds and natural openings. The important symptoms are

1. Leaf spot

·      Symptom include the appearance of water soaked, circular or irregular, necrotic spot on leaves. Sometimes the spots are encircled with a yellow halo.

·      Eg. Bacterial leaf spot in tomato : X. axonopodis. pv. vesicatoria,

Angular leaf spot in cotton : X. a. pv. malvacearum

Bacterial leaf streak in paddy : X. oryzae. pv. oryzicola

2. Leaf blight

·      Rapid and extensive necrosis of affected eaves resulting in scorched appearance.

·      Eg - Bacterial blight in paddy : X. oryzae. pv. oryzae

       Bacterial blight in beans : X.c. pv. phaseoli.

3. Soft rot

·      Affected area is soft, watery, discoloured and somewhat depressed, or wrinkled or blistered.

·      Eg. Soft rot of carrot caused by Erwinia carotovora pv. carotovora.

4. Canker

·      Formation of corky outgrowth on the surface of leaves, swigs and fruits as a result of necrosis of host

·      Eg. Citrus canker : Xanthomonas axonopodis. pv. citri,

Bacterial canker in mango : Xanthomonas axonopodis pv. mangiferae indica

5. Scab

·      The infected area becomes rough, corky, slightly raised with rusty surface and pitted due to the abnormal proliferation of tissues in the epidermis. It is only by epidermal infection and are not deep seated.

·      Eg. Potato scab: Streptomyces scabies

6. Galls and tumours

·      Development of elongated (or) irregular targe sized outgrowth on the affected plant part due to the hypertrophy and hyperplasia of cell.

·      Hypertrophy - abnormal increase in size of individual cells

·      Hyperplasia - abnormal increase in number of cells

·      Eg - Crown gall in apple – Agrobacterium tumefaciens.

7. Wilt

·      Yellowing, dropping, wilting and death of the above ground parts of the plant.

·      Eg. Bacterial wilt in solanaceous plants: Pseudomonas solanacearum

 

 

 

 

 

 

 

 

 

 

 

 

GENERAL INTRODUCTION TO VIRUS, VIROIDS

Ø Study of plant virus is called Plant Virology

Ø The term virus was derived from ‘Latin’ word which means Poison/ venom/ slimy liquid

Ø Virus – virus is a sub-microscopic, infectious, obligate intracellular parasite which do not replicate without host

Ø Capsid – protein coat or shell which encloses the viral genome

Ø Vector – An agent/ organism which carries virus

Ø Bacteriophage  - virus which infects the bacteria (which means bacteria eater)

Ø General characters of plant viruses

·      Virus is acellular which only contains singe type of nucleic acid, either DNA or RNA

·      They are smaller than bacteria, and can pass through bacteriologic filter

·      Contains Nucleic acid (NA), packed inside the protein coat

·      Plants viruses transmitted through seeds, vegetative propagation, mechanical and vectors.

Ø Morphology, structure of plant viruses

·      All plant viruses contains two major components i.e. nucleic acid and protein coat

·      Nucleic acid (NA) is considered as infectious material of plant virus, which is protected or coved by protein coat

·      COMPOSITION OF VIRUSES: Plant viruses contain selective amounts of nucleic acids and protein. Viruses with isometric particles may contain between 15% and 45% nucleic acid whereas viruses with rod shaped particles have only about 5% nucleic acid. They also contain polyamines, enzymes and lipids.

 

 

 

 

Short note on TMV

·      Positive (+) ss RNA viruses

·      TMV is a rod shaped which measures about 300 × 15-18 nm

·      TMV contains 158 amino acids

·      TMV contains 2130 capsomere subunits

·      TMV contains approximately 6400 nucleotides.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VIROIDS

·      Viroids – Small circular, single standard RNA without protein coat(nucleic acid devoid of protein coat), consists of 250-370 nucleotides

·      Viroid was 1^st discovered by Diener (1971)

·      1^st viroid disease – Potato spine tuber viroid

·      Examples – Potato spindle tuber viroid (357-359 nucleotides)

        Citrus exocortosis viroid (371 nucleotides)

        Coconut cudang cudang viroid (246 nucleotides)

General characters of viroid

·      Viroids are circular, single stranded pathogenic RNAs of few hundred nucleotides long (240 – 400nt) smallest of known agents of infectious diseases.

·      They do not code for any protein and are replicate independently of any associated plant virus

·      They lack protein coat

Difference between virus and viroid

Virus	Viroid
Discovered by Beijerinck (1898)	Discovered by Diener (1971)
Infects all types of organisms (both plants and animals)	Infects only plants
Contains protein coat	Contains no protein coat
Contains genetic material as DNA or RNA, but not both	Only RNA as genetic material
Transmitted by insects, seeds and pollen	Mainly mechanical or contact
Rod and spherical in shape	Circular in shape
Eg - TMV	Eg – Potato spindle tuber viroid

 

 

 

 

COMMON SYMPTOMS OF VIRAL DISEASES

 

‘Symptoms’ are the manifestation of the effects that a virus causes on the growth, development and metabolism of an infected host plant, which are mostly visible to the naked eye.

Common symptoms

1. Reduction in growth

·      Reduced plant height

·      Almost all parts show reduction

2. Mosaic and related symptoms

·      Development of patternof dark green and light green areas giving mosaic effect

·      Seen on leaves and fruits

·      Eg. Tobacco mosaic virus, Cucumber mosaic virus

3. Chlorosis

·      Whole leaf become yellow due to loss of chlorophyll

·      Chlorosis confined to the vein – Vein clearing

·      Eg. Bhendi yellow vein virus

4. Ringspotting

·      One or more concentric rings of dead cells with normal green tissue between them

·      Eg. Tobacco ring spot virus, Papaya ring spot virus, Tomato spotted wilt virus

5. Necrosis

·      Death of tissue, organs or whole plant

·      Eg. Potato virus X, Potato virus Y

6. Abnormalities in growth of leaves

·      Texture of leave become thick and brittle

·      Veins become unusually thickened

·      Leaves become smaller, mishappened and blistered

·      Eg., Papaya ring spot virus, CMV on tomato

7. Enation or tumours

·      Outgrowth from upper or lower surface of leaves

·      Eg. Pea enation mosaic virus

8. Symptoms on stem and Roots

·      Tumours are produced on the stem and roots of woody plants

·      Eg. Cocao swollen shoot virus – Swollen stem on cocao plant

·      Wound tumour virus – Tumours on roots of clover

9. Flower symptom

·      Color breaking on flowers

·      Reduced size, deformed shape and reduced flowering

·      Eg. Tulip color breaking virus

10. Abnormalities in Fruits, Seeds and Pollens

·      Color change on fruits, Mottling, ring spotting and necrotic symptoms, distorted and mishappened

·      Eg. Cucumber mosaic virus on cucumber

 

 

 

 

 

 

 

 

 

 

 

 

 

PHYTOPLASMA AND SPIROPLASMA

PHYTOPLASMA

·      Lack of cell wall, pleomorphic and filamentous shape

·      Discovered by Doi et al., 1967

·      Initially called as mycoplasma like organisms (MLOs), then renamed as phytoplasma in 1994

·      Contains both DNA and RNA as genetic material

·      Size ranges from 0.1 – 1 µm

·      Phytoplasma cannot be cultured on artificial media

·      Transmitted by leafhoppers, plant hoppers and psyllids but not seeds

·      Resistant to penicillin and sensitive to tetracycline

·      1^st phytoplasmal disease – Mulberry dwarf

·      Eg – Little leaf of brinjal

        Sesame phyllody

        Coconut lethal yellowing

        Rice yellow dwarf

        Apple proliferation

SPIOPLASMA

·      It is the smallest, wall less, helical, self-replicating prokaryote

·      Discovered by Davis et al., 1972

·      Contains both DNA and RNA

·      It can be cultured in the artificial nutrient media

·      Cultural colonies are appeared as fried egg appearance

·      Resistant to penicillin and sensitive to tetracycline

·      1^st spiroplasmal disease – Corn stunt

·      Eg – Citrus stub born

                                    Pear decline

Fastidious vascular bacteria

·      Previously called as rikettsia like organism (RLO)

·      Cause plant diseases and cannot be grown on artificial media

·      Limited only fastidious to xylem/phloem.

Important fastidious vascular bacterial diseases

1) Xylem inhabiting fastidious bacteria

    i) Grame positive

a) Sugarcane ratoon stunting (Clavibacter xyle subsp. Xyli).

    ii) Gram Negative - Xylella fastideosa

a) Pierce's disease of grapes

b) Citrus variegation

c) Peach phony disease

d) Plum leaf scald

e) Almond leaf scorch

2) Phloem inhabiting fastideous bacteria (Gram negative)

a) Citrus greening

b) Clover club leaf

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

SOME IMPORTANT FUNGAL DISEASES AND THEIR CAUSAL ORGANISMS

Oomycota –

·      Damping off – Pythium aphanidermatum

·      White rust of crucifers – Albugo candida

·      White rust of amaranthus – Albugo bliti

·      Late blight of potato – Phytophthora infestans

·      Downy mildew of grapes – Plasmopara viticola

·      Downy mildew/ green ear of cumbu – Sclerospora graminicola

Chytridiomycota –

·      Potato wart – Sychytrium endobioticum

·      Jack fruit rot – Rhizopus atrocarpi

Ascomycota

·      Peach leaf curl – Taphrina deformans

·      Banana sigatoka leaf spot – Mycosphearella musicola

·      Brown leaf spot of rice – Helminthosporium oryzae/ Bipolaris oryzae

·      Early blight of tomato and potato – Alternaria solani

·      Apple scab – Venturia inaequalis

·      Root rot of pulses – Macrophomina phaseolina

·      Rice blast – Pyricularia oryzae

Basidiomycota

·      Button mushroom – Agaricus bisporus

·      Milky mushroom – Calocybe indica

·      Paddy straw – Volvariella volvacea

·      Oyster mushroom – Plerotus sojar caju

·      Sheath blight of rice – Rhizoctona solani

·      Wheat stem rust – Puccinia graminis tritici

·      Coffee rust – Hemileia vastratrix

·      Flax seed rust – Melampsora lini

 

 

 

 

PHANEROGAMIC PLANT PARASITES AND NEMATODES

Phanerogamic plant parasites depend upon another vascular plant for food and water.

All the Phaenerogamic parasites can absorbs nutrients through haustoria

Complete stem parasite	Cuscuta
Partial stem parasite	Loranthus/ Dendrophthoe
Complete root parasite	Orobanche (Broom rape)
Partial root  parasite	Striga (Witch weed)

 

Characteristics of Flowering Parasitic Plants

      ·         The pathogenic flowering plants, also called parasitic angiosperms can be classified as root parasites or stem parasites.

      ·         Root parasites (witchweed and broomrape) are more common and more diverse

taxonomically.

      ·         Stem parasites include the dodder (Cuscuta) and mistletoes (Arceuthobium).

      ·         The angiospermic parasites can also be classified as holoparasites (total parasites) or

hemiparasites (semiparasites).

      ·         The holoparasites lack chlorophyll and are totally dependent on the host for nutrition. Thus, they are obligate parasites.

      ·         The hemiparasites contain chlorophyll and make their own food, and absorb water and minerals from their host. But, in some cases, e.g., Arceuthobium, the photosynthesis is negligible and the parasite draws nutrition from the host. Practically, it is an obligate parasite.

 

Cuscuta                                        Loranthus

                            

          Orobanche                                           Striga

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

NEMATODES

Study of nematodes – Nematology

Father of modern nematology – N. A. Cobb

Nematode	Scientific name / causal organims
Wheat/ rye ear cockle nematode (seed gall nematode)	Anguna tritici
Cyst nematode	Heterodera, Globodera
Dagger nematode	Xiphinema
Stubby root nematode	Trichodorous
Potato cyst nematode/ Potato root  nematode	Globodera rostochiensis
Golden nematode Golden eelworm or  Yellow potato cyst nematode	Globodera rostochiensis
Reniform nematode	Rotylenchulus reniformis
Banana burrowing nematode	Rhadopholus similis
Rice white tip nematode/ leaf and bud nematode	Aphelenchoides besseyi

 

 

 

 

 

 

 

 

 

PLANT DISEASE EPIDEMIOLOGY

Ø Epidemiology or epiphytology is the study factors influencing the outbreak of an infectious disease.

Ø Epidemics otherwise called as - Epiphytotics

Ø Epidemiology otherwise called as - Epiphytology

1.   Endemic – A disease which more or less present constantly from year to year in a

particular area.

ü Eg. Potato wart disease in Darjeeling area, Club root disease of cabbage is endemic in the Nilgiris district

2.   Sporadic – A disease when occurs at irregular intervals, location and in relatively few

instances

ü Eg. Angular leaf spot of cucumber, Udubatta disease in rice

3.   Epidemic / Epipytotic – A disease which occurs in a severe form over a larger area for a limited period

ü Eg. Brown spot of rice, Powdery mildew disease in grapevine

4.   Pandemic – When a disease is prevalent throughout the country, continent or world

ü Eg., Late blight of potato, coffee rust, Damping off disease in Tomato.

Plant disease triangle

There are three main components of a disease               

1. Host – Agent/ organism which harbours/   supports the activities of a pathogen

2. Pathogen – Organisms which are responsible for the initiation of disease. The pathogen draws nutrients and interferes with metabolism of plant.

3. Environment – Different environmental factors affects the development and spread of the disease. The environmental includes temperature, sunlight, humidity, rainfall, pH etc. Here environment plays a major role in survivability and spread of inoculum.  

Types of Epidemics

1.   Rapid Epidemic / Compound interest disease

·      Pathogen multiply at a higher rate within a short period leads to rapid increase of disease

·      Eg. Late blight of potato, Stem rust of wheat, Powdery mildew of wheat

2.   Slow epidemic / Simple interest disease

·      Infection take several years to become epidemic

·      Eg. Vascular wilts, Soil borne smuts

 

Causes of epidemic

·      Inoculum potential

·      Unnatural culture

·      Introduction of a disease to a new area – Eg. TN1 rice variety from Japan – BLB susceptible

·      Due to plant breeding – Eg. HB3 Cumbu – highly susceptible to downy mildew

 

 

 

 

 

 

 

 

DISEASE SURVEY AND ASSESSMENT

1.   Methods of Survey

a)   Fixed plot survey

Select two villages and fix two fields per village. Select 5 sampling plots per field of

one acre away from bund. Sample plot size is 1sq. m. Select 20 plants or leaves per plot.   

b)  Roving survey

Select four villages and fix two fields in each village. Observe and score 100plants or

leaves by walking across field in each field.

Disease surveillance reports

i.     White card – Contains disease / pest surveillance detail in a particulr block/ division /

district for a week.

ii.   Yellow card – When the disease / pest occurrence attained half the level of ETL

iii. Red card - When the disease / pest occurrence exceeded ETL.

 

2.   Disease assessment

a)   Assessment in terms of percentage

·      Applicable for disease which cause complete death of plants (Eg. Damping off, Root rot, wilt, etc.), systemic diseases (eg. Virus, Phytoplasma, etc.,) and in diseases leading to total destruction of infected organs (eg., Smut, greenear, etc.,)

Percent disesase incidence = (No. of plants infected / No. of plant observed) x 100

b)  Assessment using disease grades

·      Applicable for the foliar diseases like downy mildew, powdery mildew, leaf spot, leaf blight, canker, rust, etc.

 

 

                  DISEASE FORECASTING

Forecasting: Advance warning to prevent the outbreak of the disease.

Computer simulation models 

Sl.no	Forecasting model	Diseases name	Causal organism
1	EPIDEM	Early blight of Potato, Tomato	Alternaria solani
2	EPIMAY	Southern leaf blight of maize	Heliminthosporium maydis
3	EPICORN	Southern corn blight	Heliminthosporium maydis
4	CERCOS	Blight of celery	Cercospora spp
5	MYCOS	Blight of chrysanthemum	Mycosphaerella spp
6	EPIVEN	Apple scab	Venturia inaequalis

 

Difference between vertical and horizontal resistance

Particulars	Vertical resistance	Horizontal resistance
Efficiency	Resistance is strong, but effective against one or few races of pathogens,	Partial resistance which is weak, but equally effective against to all races of pathogens
Other names	Major gene Race specific	Minor gene resistance Race nonspecific
Controlled by	Major genes	Minor genes
Nature of gene action	Oligogenic	Polygenic (rarely oligogenic)
Selection and evaluation	Comparatively easy	Comparatively difficult
Host pathogen interaction	Present	Absent
Examples	Kufri Naveen, kufri jeevan	IR 20

 

 

DISPERSAL OF PLANT PATHOGENS

SEED

Seed borne fungal disease

Externally seed borne

·      Brown spot of rice, Wheat bunt, Sorghum grain smut, Sorghum loose smut, Sorghum head smut, Chilly fruit rot, Bean anthracnose

Internally seed borne

·      Loose smut of wheat, Barley loose smut

Infected tubers

·      Late blight of potato, Black scurf of potato

Through setts

·      Sugarcane Whip Smut, Red rot, Wilt of sugarcane

Through ratoon stumps

o   Sugarcane Whip Smut, Red rot

Seed borne bacterial disease

·      BLB, Bacterial leaf streak of rice, Black arm of cotton, Black rot of cabbage, Brown rot of potato, Tundu disease of wheat

·      Cornybacterium tritici alone cause Yellow ear rot of wheat

·      Anguina tritici cause Ear cockle disease / Tundu disease

Seed borne viral disease

·      Bean, Soybean, Lettuce Mosaic virus, Bean common mosaic virus, Tobacco mosaic virus, Cucumber mosaic virus, etc.,

INSECTS

Fungi spread by insects

·      Puccinia graminis tritici in wheat, Claviceps purpurea in rye, C. fusiformis in cumbu,

·      Sphacelia sorghi in sorghum through ants and honey bees

·      Dutch elm disease (Ceratocystis ulmi) by bark beetle (Scolytes multistriatus)

Bacteria spread by insects

·      Erwinia amylovora in apple – Honey bees

·      Xanthomonas stewartii in maize – Corn flea beetle (Chaetonema pulicaria)

VIRUSES TRANSMITTED BY INSECTS

Aphids

·      Pentalonia nigronervosa – Katte disease of cardomom, Banana bunchy top virus

·      Toxoptera citricida – Citrus triteza virus

·      Aphis craccivora – Groundnut rosette, Bean common mosaic, Pea mosaic

·      gossypii – Chilli mosaic

·      Myzus persicae – Papaya ring spot virus

Thrips

·      Scirtothrips dorsalis, Frankliniella schultzii, Thrips tabacci – Greengram leaf curl virus,

·      Groundnut bud necrosis virus, Tomato spotted wilt virus

Leaf hoppers (Jassids)

·      Nephotettix virescens, N. impicticeps (GLH) – Rice tungro virus, Rice dwarf virus

·      Nilaparvatha lugens (BPH) – Rice ragged stunt virus

Whiteflies

·      Bemisia tabaci – Bhendi yellow vein clearing, Blackgram leaf crinckle, Cassava mosaic,

·      Leaf curls (Chilli, Tomato, Cotton, Tobacco)

Mites

·      Aceria cajani – Redgram sterility mosaic virus

Mealy bug

·      Cocoa swollen shoot disease – Planococcus njalensis

Insects transmitting Phytoplasma (Only Leaf hoppers)

·      Nilaparvata lugens – Rice yellow dwarf disease

·      Hishimonas phycitis – Brinjal little leaf

·      Orosius albicinctus – Sesamum phyllody

·      Rhaphalosiphum maydis – Sugarcane grassy shoot disease

·      Nephotettix virescence & Moonia albimaculata – Sandal spike disease of sandal wood

NEMATODES

·      Anguina tritici – Tundu disease (Cornybacterium tritici) in wheat

·      Meloidogyne incognita var. acrita – Pseudomonas solanacearum in tomato

·      Longidorus – Tobacco ring spot virus (NEPO)

·      Xiphinema – Grapevine fan leaf virus (NEPO)

·      Trichodorus & Paratrichodorus – Tobacco rattle virus (NETU / TOBRA)

FUNGI

·      Olpidium brassicae – Lettuce big vein mosaic virus, CMV

·      Polymyxa graminis – Wheat mosaic virus

·      Spongospora subterranean – Potato mop top virus

·      Synchytrium endobioticum – Potato virus X

 

 

 

 

 

 

 

 

 

GENERAL PRINCIPLES OF PLANT DISEASE MANAGEMENT

Six fundamental principles of disease management are

1. Exclusion

2. Eradication

3. Protection – chemicals

4. Resistance – resistant varieties

5. Therapy

6. Avoidance of insect vectors and weed hosts.

Exclusion

·      Plant disease legislation

·      Inspection of plant product

·      Elimination of pathogen from planting material

Eradication

·      Direct removal of pathogen

·      Elimination by actual practices

·      Destruction of pathogen

Avoidence

·      Choice of geographic area

·      Selection of field

·      Time of sowing

·      Disease escape (klenducity)

·      IR-50 susceptible host to blast – sown during summer escaped from blast.

·      Selection of seed and planting materials

·      Modification of cultural practices

ü Closer spacing increase – Powdery mildew, sigatoka disease

ü Less shade –increase – tea blister blight and coffee rust

ü Mixed cropping of pulse and Cumbu reduce yellow mosaic incidence.

Exclusion

·      Exclusion is to prevent the spread of disease when avoidance failed

·      It can be achieved by

ü Seed certification

ü Crop inspection

ü Plant quarantine

 

Eradication from seeds and seed materials

Mechanical

·      20% brine solution

Physical

·      Steam at 52 – 540 c for 20 mins – ex. BLB and Blast

·      Sugarcane grassy shoot – hot water treatment 500 c for 2 – 2.30 hrs

·      Hot air @ 500 c for 8 hrs

·      Aerated steam theraphy at 500 c for 1 hr

·      Moist hot air treatment – 54 0 c for 2 hrs

·      Luthra solar treatment – loose smut of wheat.

Eradication of infected / diseased plants

1.   Sanitation

2.   Surgery and rouging

3.   Eradication of alternate host / collateral host

4.   Crop rotation

Successful for

a. Pathogens live in soil for short time

b. Having short host range

c. Annual diseases

5.   Mixed cropping

6.   Modifying soil reaction

a.    Application of lime –Reduces club root of cabbage & Brown rot of potato

b.   Application of Gypsum – Reduces Potato scab & wilt of cotton

7.   Cultural practices

8.   Eradications of pathogens in soil

Protection – Accomplished by the application of chemicals to the plats

i.     Protection from air borne disease

ii.   Protection from seed borne disease

iii. Protection from soil borne disease

a. Physical method

ü Soil solarisation – Irrigate field upto 10 cm depth and cover the soil with polythene sheet after 2 days of and leave it undisturbed for 4-6 weeks.

ü Steaming

ü Direct flaming – Burning plant residues to manage disease caused Pythiumspp. and Red rot.

ü Hot water

b. Chemical method

c. Biological method

Immunization

      ·         Process of developing resistance in plants to diseases

      ·         Best way is planting resistant variety

      ·         Immune plants never affected by the pathogens

Resistance – Ability of the plant to reduce or retard the attack of pathogen

Methods of developing resistance variety

i. Introduction

ii. Pureline selection

iii. Crossing and hybridization

iv. Mutation – X ray, UV, Gamma & chemical mutagens

 

 

 

PLANT QUARANTINE

·      Quarantine - 40

·      Legal registration on the movement of plants and plant materials between countries and between states within the country in order to prevent the establishment and

·      introduction of diseases.

Regulations

·      First quarantine law – France, 1960 – prevent spread of barberry plants

·      First quarantine act – USA, 1912

·      Destructive insects and pests act, 1914 – India.

·      Quarantine offices in India – Mumbai, Cochin, Chennai, Calcutta, Vizagapattinam.

·      Airports – Amritsar, Mumbai, Chennai, Calcutta, New Delhi.

·      NBPGR – National Bureau of Plant Genetic Resources involved in import / export of plant materials.

CLASSIFICATION OF QUARANTINE

·      Exclusive – Prohibition of importation of plant materials.

·      Regulatory – import permitted if accompanies “Phytosanitary certificate” Also

1.   DOMESTIC: Restricts spread of a disease with in a country from one place to another with in state or between states.

·      In TN Madras Agricultural pests and diseases Act, 1919 - Control of sandal spike, Cardamom mosaic, Orabanche, Wheat stem rust, blister blight.

·      In INDIA DIP Act 1914.

ü Prevent spread of BBTV from Assam, Kerala, Orissa, Tamil Nadu andwest Bengal.

ü Prevent spread of potato cyst nematode from TN.

2.   INTERNATIONAL (Foreign)

·      Coffee leaf rust – Hemilieavastatrix (Srilanka)- 1940

·      Late blight of potato – Phytophthorainfestans(Srilanka)- 1883

·      Banana bunchy top virus- (Srilanka)-1940

·      Paddy blast- (Srilanka)-1918

·      Cardamom suckers – prohibited from Anamalais to avoid Katte mosaic virus

3.   Embargo

Total prohibition on import or export of transport of plant material in a country. Categorization of quarantine restrictions:

·      Unrestricted

·      Restricted – require phytosanitary certificate

·      Post entry quarantine

·      Prohibited – require phytosanitary certificate and import permit

Eradication

1.   Aims at killing of pathogen that have already gained entry in to the country.

 

 

 

 

 

 

 

 

 

 

FUNGICIDES AND ANTIBIOTICS, BIOLOGICAL CONTROL

LANDMARKS

      ·         1882 – P.M.A. Millardet of France – Used Bordeaux mixture on the control of downy mildew of grapes

Terminologies

      ·         Fungicide is a chemical capable of killing fungi

      ·         Fungistat - chemicals do not kill but simply arrest the growth of the fungus

      ·         Antisporulant - chemicals that inhibit the spore production without affecting the vegetative growth

Fungicides grouping:

1.   Mode of action

                   ·         Protectant - effective only if applied prior to fungal infection eg., Zineb, Sulphur

                   ·         Therapeutant - Capable of eradicating a fungus after it has caused infection and there by curing the plant eg. Carboxin, Oxycarboxin antibiotics like Aureofungin

                   ·         Eradicant - eradicate the dormant or active pathogen from the host. eg. Organic mercurials, lime sulphur, dodine etc.

2.   Based on general use

i.     Seed protectants: Eg. Captan, thiram, organomercuries carbendazim, carboxin etc.

ii.   Soil fungicides (preplant): Eg. Bordeaux mixture, copper oxy chloride, Chloropicrin, Formaldehyde Vapam, etc.,

iii. Soil fungicides (for growing plant): Eg. Bordeaux mixture, copper oxychloride, Capton, PCNB, thiram etc.

iv. Foliage and blossom protectant: Eg. Capton, ferbam, zineb, mancozeb, chlorothalonil etc.

v.   Fruit protectants: Eg. Captan, maneb, carbendazim, mancozeb etc.

vi. Eradicants: Eg. Organomercurials, lime sulphur, etc.

vii. Tree wound dressers: Eg. Boreaux paste, chaubattia paste, etc.

viii.                 Antibiotics: Eg. Actidione, Griseofulvin, Streptomycin, Streptocycline, etc.,

Based on chemical Nature

i.     Mercurial fungicides

ii.   Copper fungicides

iii. Sulphur fungicides

iv. Quinones

v.   Heterocyclic nitrogenous compounds

vi. Aromatic compounds

vii.                 Non – aromatic compounds

viii.               Organotin compounds

ix. Organophosphorus compounds

x.   Nickel compounds

xi. Miscellaneous fungicides

xii.                 Systemic fungicides

xiii.               Antibiotics

1. Mercury fungicides -

2. Composition of copper fungicides

Compound	Scientist	Year	Composition	Uses/ disease managed
Bordeaux mixture	P.M.A. Millardet	1882	1 kg of copper sulphate, 1 kg of lime, 100 lit of water                      (1:1:100)	Downy mildew of grapes, blights and anthracnose
Burgundy mixture	Masson	1887	1 kg of copper sulphate, 1 kg of sodium carbonate, 100 lit of water                      (1:1:100)
Chestnut compound	Bewely	1921	2 parts of copper sulphate 11 parts of ammonium carbonate (2:11)	Pythium damping off
Chaubattia paste	Singh	1942	copper carbonate -800 g, red lead -800 g linseed oil or lanolin -1littre                           (800gm:800gm:1 lit)	Damping off of seedlings

3. Sulphur fungicides

i.     Inorganic – WP, Dust (Kosam, Thiovit)

ii.   Organic – (Carbamate fungicides)

ü Monoalkyl dithiocarbamates – Zineb, Maneb, Mancozeb, Nabam, Vapam

ü Dialkyl dithiocarbamates – Thiram, Ziram, Ferbam

4. Quinone fungicides

      ·         Chloranil – Spergon

      ·         Dichlone – Phygon, Phygon XL

5. Heterocyclic nitrogen compounds

      ·         Captan, Folpet, Captafol, Vincozolin (rolinan), Iprodione

6. Aromatic compounds

      ·         Quintozene (PCNB) – Brassicol, Terraclor (Soil treatment)

      ·         Dinocap – Karathane, Arathane

7. Non-Aromatic compounds - Dodine

8. Organotin compounds (Triphenyl tin)

      ·         Fentin hydroxide, Fentin acetate, Fentin chloride

9. Organophosphorus compounds - Ediphenphos

10. Nickel compounds

      ·         Nickel chloride – For Tea blister blight

11. Miscellaneous fungicides

      ·         Chinomethionate – Morestan (Acaricidal)

12. Systemic fungicides

i. Acetamides: e.g., cymoxanil

ii. Acylalanines: e.g., Metalaxyl, Furalaxyl, Benalaxyl

iii. Aliphatics: e.g., prothiocarb, Propamocarb

13. Antibiotics

Chemical substance produced by one microorganism which in low concentration can inhibit or even kill other microorganisms.

i.     Antibacterial antibiotics - Streptomycin, Tetracycline

ii.   Antifungal antibiotics – Aureofungin, Griseofulvin, Cycloheximide, Blasticdin, Antimycin, Kasugamycin

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

BIOLOGICAL CONTROL

Biological control - reduction of inoculum density or disease producing activities of a Pathogen by introduction of one or more antagonists. Biological control is nothing but control of plant diseases using living microorganisms.

The four main mechanisms involved in the biocontrol are

(i) Parasitism - antagonist parasite the other organism,

(ii) Antibiosis - antagonist may secrete harmful metabolites

(iii) Competition - antagonist may compete with the pathogens for nutrients or space

(iv) Lysis - may cause death of the parasite by producing enzymes

Fungal biocontrol agents

      ·         Trichoderma viride

      ·         Chaetomium globosum (Gliocladium virens)

      ·         Trichoderma harzianum

      ·         T. hamatum

      ·         Paecilomyces lilacinus (Verticillium leccani)

      ·         Pochonia chlamydosporia

      ·         Laetisaria arvalis

Bacterial bioconrol agents

      ·         Pseudomonas fluorescens

      ·         Bacillus subtilis

      ·         B. thuringiensis

      ·         Streptomyces griseoviridis

      ·         Agrobacterium radiobacter

      ·         Pasteuria penetrans (for RKN)

 

 

 

 

MUSHROOMS

Group of fleshy macroscopic fungi or large fleshy fruiting bodies of some fungi or large

reproductive structures of edible fungi belonging to two sub divisions viz. Ascomycotina

and Basidiomycotina.

·      Grow epigeal or hypogeal.

·      Edible fruiting bodies – mushroom

·      Poisonous - toadstools (death chair).

·      Silver ear / Jelly fungus - Tremella fuciformis

·      Morels - Morchella

·      Truffles - Tuber

·      Pine mushroom - Tricholoma mastsutake

·      Shaggy mushroom (Inkcap) – Coprinus comatus

·      Honey fungus / Honey Agaric / Shoestring mushroom – Armillaria mellea

·      Edible Boletus – Boletus edulis

Common cultivated mushrooms

·      Paddy straw mushroom - Volvariella spp.

·      Oyster mushroom - Pleurotus spp.

·      Button mushroom - Agaricus spp.

·      Milky mushroom - Calocybe spp.

·      Shiitake mushroom - Lentinus spp.

·      Jew’s ear mushroom - Auricularia sp.

 

Parts of mushroom

      ·         Mycelium

      ·         Cap / Pileus

      ·         Stipe / Stalk

      ·         Gills / Lamellae

      ·         Veil – Inner veil (Annulus) & Universal veil (Volva)

ü Both annulus and volva present           e.g., Amanita

ü Only annulus present and volva absent  e.g., Agaricus

ü Only volva present and annulus absent e.g., Volvariella

ü Both annulus and volva absent            e.g., Marasmius oreades

 

 

              

 

Poisonous Mushroom

      ·         MYCETISM - mushroom poisoning

      ·         Due production of toxins

ü Amanitin - Amanita phalloides, A. verna, A. verosa

ü Helvella poisons - Helvellea esculenta, H. gigas

ü Muscarine toxins - Amanita muscaria, A. pantherina, Boletus spp.

ü Pilzatropin - A. muscaria, A. pantherina

ü Psilocylin and Psilocin - Psilocybe, Panaeolus, Russula

Important Poisonous Mushrooms

      ·         Amanita muscaria - Fly agaricus

      ·         Amanita pantherina - Panther cap

      ·         Amanita phalloides - Death cap

      ·         Amanita verna - Fool’s mushroom

      ·         Amanita virosa - Destroying angel

      ·         Psilocybe spp. - hallucinogenic effects

 

Difference between edible and poisonous mushrooms

Particulars	Edible mushrooms	Poisonous mushrooms
Pileus colour	White or light coloured	Brightly coloured from yellow to brown
Pileus shape	Radial	Triangular
Stipe	Stout and fleshy in nature	Stiff and hallow in nature
Stipe length	Short	Long
Annulus	Present	Absent
Vovla	Absent	Present (Volvariellla volvacea is an exception)
Exudations	No exudations	Milky substances
Flavour/ smell	They have pleasant flavour/ smell	Unpleasant smell
Colour and taste	Won’t change  while cooking	Unusual change of odour and taste
Phytoplasmic toxins	Absent	Present 1.   Phallotoxin  (Amanita phalloides) 2.   Amanotoxin (A. virosa)
Examples	Agaricus bisporus, Calocybe indica	Amanita phalloides, Amanita virosa

 

 

 

Comparison of important commercially cultivated mushrooms

Character	Oyster Mushroom	Button Mushroom	Milky Mushroom (APK2)	Paddy Straw Mushroom
Scientific Name	Pleurotus sp.	Agaricus spp.	Calocybe indica	Volvariella spp
Substrate	Paddy straw	Compost	Paddy straw	Paddy straw
Growing temperature	20-25oC	15-20oC	30-35oC	30-35oC
Required RH	Above 80 %	85-95 %	Above 85 %	85 - 90 %
Crop cycle	40-45 days	85-100 days	45-50 days	25-30 days
Days for first harvest	15-25 days	60-70 days	24-28 days	10-15 days
Yield per bed	400-600 g / 500g bed	20-25 kg/100 kg compost	250-350 g / 250g bed	5 kg / 30 kg bed
Shelf life	1-3 days	3-5 days	3-5 days	1-3 days
Bioefficiency	80-120%	20-30%	100-150%	15-20%

 

 

 

 

 

 

 

 

 

 

POST HARVEST DISEASES OF STORAGE GRAINS

Losses

      ·         Fruit & vegetables – 20-30%

      ·         Food grains – 9.3%

      ·         Post-harvest disease occurs in transit and storage are mainly due to the activity of fungi, bacteria and of non-parasitic origin.

Effects of storage fungi on grains

1. Decrease the germination

2. Reduce the quality of grains

3. Cause discoloration of seeds

4. Produce toxins in stored grains

5. Cause biochemical changes and damage seeds

6. Cause heating and affect quality

Aflatoxin produced by Aspergillus flavus in groundnut, which is highly toxic. Heating

favours growth of storage fungi. At higher temperature (45^oC) grains get killed.

i.     Aspergillus flavus & A. glaucus - 45^oC

ii.   Mucor - 30^oC

iii. Fusarium - 35^oC

iv. Alternaria - 25^oC

Fungus require Moistrure content of about Aspergillus flavus – 17.5 – 18%

Aspergillus candidus – 15 – 15.2%

A. restrictus – 13.2 – 13.5%

Management

      ·         Harvest and store the crops at optimum moisture content 12-13% and temperature 12- 15^oC

      ·         Fumigate the storage godowns

      ·         Provide proper ventilation to storage godowns

 

 

Disease of vegetables and fruits

Infection may occurs before harvesting, during post harvest handling or storage. Ripened

fruits are infected easily, while green fruits show resistance. Reasons are,

1. Nutritional requirement of fungus is not met out by the fungus

2. Higher enzyme potential is needed to invade greenfruits

3. Phenolics and some other toxins present in the green fruits

4. Energy requirement of fungus is met out in ripening stage of fruit only.

Causal organism

      ·         Biotic factors

Soft rot producing bacteria, Fungus due to predisposing factors such as humidity, temperature, presence of bruises or lesions on fruits and vegetables

      ·         Abiotic factors

When fruits and vegetables stored in poor ventilated conditions such s High level of CO2, Low O2 post-harvest disease may happen.

Black heart of apple and Potato – caused by lack of oxygen (High temp, poor ventilation)

 

Write short notes on important post-harvest diseases of fruits and vegetables

Fruits/ vegetables	Diseases	Causal organisms
Apple, Pear	Blue mould	Penicillium expansum
	Grey mould	Botrytis cinerea
	Lentil rot	Gloeosporium album
Banana	Crown rot	Colletotrichum musae, Fusarium roseum
	Anthracnose	Colletotrichum musae
Citrus (lemon, orange etc)	Grey mould	Botrytis cinerea
	Blue mould	Penicillium italicum
	Green mould	Penicillium digitatum
	Stem end rot	Phomopsis citri, Alternaria ciri
	Sour rot	Geotrichum candidum
Grape	Grey mould	Botrytis cinerea
Peach	Brown rot	Sclerotinia fructicola or Monilinia fructicola
	Rhizopus rot	Rhizopus stolonifer
Mango	Anthracnose	Colletotrichum gloeosporiodes
Cherry	Brown rot	Sclerotinia fructicola or Monilinia fructicola
Strawberry	Grey mould	Botrytis cinerea
	Rhizopus rot	Rhizopus stolonifer
Pineapple	Black rot	Ceratocystis paradoxa
Potato	Bacterial soft rot	Erwinia carotovora
	Dry rot	Fusarium sp.
Sweet potato	Black rot	Ceratocystis fimbriata
Carrot	Watery soft rot	Sclerotinia sclerotiorum
Leafy vegetables	Grey mould	Botrytis cinerea
	Bacterial soft rot	Erwinia carotovora
	Watery soft rot	Sclerotinia sclerotiorum

 

 

 

 

 

 

 

 

 

VECTORS INVOLVED IN VIRUS DISEASES SPREAD

Name of the disease	Vector
APHIDS
Potato virus Y (Poty virus)	Myzus persicae
Potato leaf roll virus (PLRV)	Myzus persicae
Bean common mosaic virus	Aphis craccivora
French bean mosaic virus	Aphis craccivora, A. gossypii, Myzus persicae
Chilli mosaic virus	Aphis craccivora, A. gossypii
Cucumber mosaic virus	Aphis craccivora, A. gossypii
Papaya ring spot virus (PRSV)	A. gossypii, Myzus persicae
Katte disease of cardamom	Pentalonia nigronervosa
Banana bunchy top	Pentalonia nigronervosa
Alfaalfa mosaic	Acryrthosiphon pisum
Lettuce mosaic	Myzus persicae
Soybean mosaic	Aphis gossypii
Sugarcane mosaic virus	Rhopalosiphum maidis
Groundnut rosette	Aphis craccivora
Citrus tristeaza virus (Citrus quick decline)	Toxoptera citicidus
Cauliflower mosaic virus	Myzus persicae
Grassy shoot of sugarcane (Phytoplasma)	Rhopalosiphum maidis
WHITEFLY
Cotton leaf curl virus	Bemisia tabaci
Yellow mosaic of legumes	Bemisia tabaci
Yellow vein mosaic of bhendi	Bemisia tabaci
Leaf curl of cotton, Tobacco, Tomato, Chilli, Papaya, etc	Bemisia tabaci
Cassava mosaic virus	Bemisia tabaci
Cowpea mild mottle	Bemisia tabaci
Tomato yellow leaf curl	Bemisia tabaci
Squash leaf curl	Bemisia tabaci
Bean golden mosaic virus	Bemisia tabaci
Horse gram yellow mosaic	Bemisia tabaci
LEAF HOPPERS AND PLANT HOPPERS
Rice tungro virus	Nephotettix virescens
Rice yellow dwarf (Phytoplasma)	Nephotettix virescens
Rice stripe	Nephotettix impecticeps
Rice dwarf	Nephotettix impecticeps
Rice grassy stunt	Nilaparvatha lugens
Rice ragged stunt	Nilaparvatha lugens
Sandal spike (Phytoplasma)	Nephotettix virescens, Moonia albimaculata
Little leaf of brinjal (Phytoplasma)	Hishimonas phycitis
Sesamum phyllody	Orosius albicinctus
Grassy shoot of sugarcane (Phytoplasma)	Proutista moesta
Coconut root wilt / Kerala wilt (Phyotplasma)	Proutista moesta
Citrus stubborn (Spiroplasma)	Circulifer tenellus
Corn stunt (Spiroplasma)	Dulbulus maidis
BEETLES
Potato virus X	Epilachna ocellata
Urdbean leaf crinkle	Henosepilachna & Epilachna
Bottle gourd mosaic virus	Red pumpkin beetle
Squash mosaic virus	Diabrotica undecimpunctata
Bud rot of coconut (Phtophthora palmivora)	Orycles rhinoceros
Bacterial wilt of cucumber	Cucumber beetles
Fire blight of apple (Erwinia amylovora)	Bees, wasps, flies, beetles, etc
Dutch elm disease	Hylurgopinus rufipes
MEALY BUG
Cacao swollen shoot virus	Planococcoides njalensis
Grapevine leaf roll virus
Banana streak virus
PSYLLIDS
Citrus greening (Fastidious vascular bacteria)	Diaphorina citri
THRIPS
Tomato spotted wilt virus (Tospovirus), Groundnut bud necrosis virus	Thrips tabaci
Tobacco streak virus – Sunflower necrosis virs	Franklinella
Tobacco ring spot virus	Thrips tabaci
MITES
Pigeon pea sterility mosaic virus	Aceria cajani
Wheat streak mosaic virus	Aceria tulipae
FUNGUS
Lettuce big vein mosaic virus	Olpidium brassicae
Wheat mosaic virus	Polymyxa graminis
Potato virus X	Synchytrium endobioticum
Potato mop top virus	Spongospora subterranean
NEMATODE
Grapevine fan leaf virus	Xiphnema index
Tobacco rattle virus (Tobra / NETU)	Trichodorus
Tobacco ring spot virus	Longidorus
Tundu disease	Anguina tritici

 

 

 

ALGAE AND FLAGELLATE PROTOZOA CAUSING PLANT DISEASES

Algae

      ·         Parasitic algae are green in colour.

      ·         Cephaleuros is the best known genus, and is a plant parasite living under leaf cuticle.

      ·         It was first reported from India in the 19th century, causing damage to tea and coffee plantations.

      ·         Now, over 400 hosts of Cephaleuros are recorded all over the world infecting hibiscus, orchids, euphorbias, citrus and forest trees, and 90 percent of its hosts are dicot.

      ·         Cephaleuros belongs to phylum Chlorophtya, class Ulvophyceae, order Trentepohliales, and family Trentepohliaceae.

      ·         There are 13 species of Cephaleuros, but 6 are more common. These are: C. expansa, C. .henningsii, C. karstenii, C. minimus, C. parasiticus, and C. virescens. Among these, C. parasiticus and C. virescens are most common and cause maximum damage.

      ·         C. virescens causes red rust of tea and mango.

Red rust

      ·         Fluffy, bright-orange red spots occur on leaves and stems that look very much like rust fungi.

      ·         C. virescens has the misleading common name ‘red rust’.

      ·         Species of Cephaleuros have fungus-like filaments, sterile hairs and produce

      ·         Sporangiophores and zoosporangia on the lower surface of leaves that look like downy mildew fungi. Necrosis may be limited to the epidermis or spread into the deeper tissues of the leaves. Severe damage usually occurs on older leaves leading to defoliation.

Lichens

      ·         Fungi parasitize Cephaleuros to form lichens.

      ·         The lichenized state of C. virescens is identified as Strigula elegans.

      ·         Early literature suggests that the fungus portion of the lichen (mycobiont) was responsible for plant damage.

      ·         Recent findings show that the fungus parasitizes the alga, not the plant. Plant injury is caused by the alga much before a fungus colonizes it.

Protozoa

      ·         The protozoa as such may be living freely, or living symbiotically or as parasites subsisting on organisms such as algae, yeasts, bacteria and other protozoa.

      ·         Only the flagellates among the protozoa have been found to be associated with plant diseases. (which means the protozoa with flagella re only involved in causing plant diseases).

      ·         Eg – Club root of cabbage  - Plasmodiophora brassicae

 

 

 

 

 

 

 

 

 

 

 

 

26. Detailed Classification of Plant Diseases

1.   On the basis of their mode of perpetuation and mode of primary infection:

i.     Soil borne diseases: In these diseases, the pathogens survive in soil or on infested plant.

Eg: Damping off (Pythium sp.)

ii.   Air borne diseases: Some pathogens infects the host plant through air and bring primary as well as secondary infection.

Eg: Rusts, Powdery mildews.

iii. Seed borne diseases: Some pathogens survive as dormant mycelium in the seeds or other propagative structures of host plants.

Eg. Loose smut of wheat (internally seed borne)

2.   On the basis of their cause, diseases are classified as:

i.     Infectious plant diseases: These diseases are caused by living agents, These are characterised by the ability of the pathogen to grow and multiply rapidly.

Ex: Powdery mildews, Rusts.

ii.   Non-infectious diseases: These diseases do not spread from plant to plant (non-infectious). These diseases are caused due to abiotic factors (non parasitic or physiological).

Eg: Black heart of potato.

3.   On the basis of production and spread of the inoculum:

i.     Single cycle disease or simple interest disease: The pathogen completes entire life cycle in one year.

ii.   Multiple cycle or compound interest disease: The pathogen completes multiple cycle per year.

iii. Polyetic diseases:

Eg.: Cedar Apple Rust

4.   On the basis of plant parts affected:

i.     Localized: If they affect only specific organs or parts of the plants.

Eg.: Root Rot, Leaf spot.

ii.   Systemic: If entire plant is affected.

Eg.: Downy mildew, damping off.

5.   On the basis of group of causal organisms:

i.     Fungal disease: Caused by plant pathogenic fungi.

Eg. Anthracnose

ii.   Bacterial disease: Caused by plant pathogenic bacteria.

Eg. Citrus canker

iii. Viral disease: Caused by plant viruses.

Eg. Rice tungro disease

iv. Phanerogamic phytopathogenic diseases: Caused by phanerogamic plant parasites. Eg. Striga, Cuscutta.

v.   Nematode Diseases: Diseases caused by plant pathogenic nematodes.

Eg. Wheat Ear cockle (Anguina tritici).

6.   On the basis of occurrence and consequent effects:

i.     Endemic: When a diseases more or less constantly prevalent from year to year in a moderate to severe form in a particular country.

E.g., Wart disease of potato is endemic to Darjeeling.

ii.   Sporadic : These diseases occurs at irregular intervals and location.

Eg. Blights, Rusts.

iii. Pandemic : These diseases occur all over the world and cause mass mortality.

Eg. Late blight of potato.

iv. Epidemic or epiphytotic: A disease occurring periodically but in a severe form involving major area of the crop.

Eg. Rust, Late blight, Mildews.

v.   Pandemic: Diseases occurring throughout the continent or sub-continent resulting in mass mortality.

Eg. Late blight of potato.

7.   On the basis of organs affected:

i.     Fruit diseases: In these diseases fruits are mainly affected

Eg. Apple scab. (Venturia inaequalis)

ii.   Root diseases: In these disease, root is mainly affected.

Eg.Root rot of papaya.(Pythium aphanidermatum)

iii. Leaf diseases: Disease is localised in the foliage.

Eg. Leaf spot of cotton. ( Alternaria gossypii (Jacz.)

iv. Seedling diseases: Seedlings are affected in which stem and root tissues rot.

Eg. Damping off of seedling.(Rhizoctonia sp.)

8.   On the basis of host crop plants affected:

i.     Cereal diseases: Disease which affect cereal crops

eg. Wheat,barley and oat.

ii.   Pulses diseases: Diseases which affect pulses crop.

Eg. Ascochyta blight of chickpea.

iii. Millet diseases: Diseases which affect millets.

Eg. Green ear disease of Bajra.

iv. Vegetable diseases : Diseases which affect vegetable crops.

Eg. Early blight of Tomato (Altrnaria solani).

v.   Fruits diseases : Diseases affect fruit crops.

Eg. Apple Scab

vi. Ornamental plant diseases: Diseases affecting ornamental plants.

Eg. Chrysanthemum stunt.

vii.                 Forest diseases: Diseases affecting forest trees and plantation.

Eg. Sudden Oak Death (Phytophthora ramorum)

 

 

 

 

 

27. DISEASES OF RICE

1.   Rice blast or rotten neck - Pyricularia grisea (Perfect stage: Magnaparthae grisea)

Symptoms

i.     Leaf blast/ leaf infection

                          ·         Initially formation of reddish brown specks on the leaf blade.

ii.   Nodal blast/nodal infection

                          ·         Black discoloration on the nodal region.

iii. Neck blast/rotten neck

                          ·         Initially black discoloration on the neck region.

                          ·         Weakening of the tissue in the neck region - ear heads are broken and hang down.

iv. Grain blast

                          ·         Black irregular lesion on the grain is seen.

    Management:

               ·         Iprobenphos, Tricyclazole (neck blast), Tridemorph.

2.   Brown spot of rice / Sesamum leaf spot – Bipolaris oryzae / Cochliobolus miyabeanus.

Symptoms

               ·         Coleoptile infection - brown circular spots on first emerged leaf which leads to seedling blight.

               ·         Leaf sheath & leaf infection - circular brown leaf spot on the leaf sheath as well as on the leaf surface.

               ·         Neck infection - reddish brown lesion on the neck region but there is no rotting of the neck portion.

               ·         Nodal infection - reddish brown lesion on the nodal region.

               ·         Grain infection - reddish brown discoloration on the grain surface.

       Management

               ·         Tridemorph, mancozeb.

3.   Sheath blight of rice: Rhizoctonia solani / Thanatephorus cucumeris

Symptoms

               ·         Sheath blight: Greenish grey lesion initially seen on the sheath portion which later turns to dark brown margin and whitish grey centre.

     Management

               ·         Systemic: Carboxin, Oxycarboxin, Iprobenphos

4.   Sheath rot of rice: Sarocladium oryzae

Symptoms

               ·         Sheath infection: reddish brown lesion on the sheath enclosing the young panicle. This leads to ear head chocking. Grain discoloration (black).

Management

               ·         Tridemorph – 0.1%, mancozeb - 0.25%.

5.   Foot rot/bakanae/foolish rice: Fusarium moniliforme / Gibberella fujikuroi

Symptoms

               ·         Compared with healthy plants, infected plants are pale yellow, thin and lanky

               ·         Taller than the healthy plant and mature early.

               ·         Adventitious roots are seen in the 2nd and 3rd adventitious roots.

Management

               ·         Tridemorph - 0.1%.

6.   False smut / Lakshmi disease - Ustilaginoidea virens / Claviceps oryzae sativa.

Symptoms

               ·         At flowering stage, individual ovaries of the spikelets/grains are converted into orange yellow spore mass. Later stage it turns to greenish grey.

Management

               ·         Thiophanate methyl (Topsin M) 0.1%, Mancozeb 0.25%.

7.   Bacterial leaf blight: Xanthomonas oryzae pv. oryzae

Symptoms

               ·         Kresek / wilting: wilting of entire plant within 30 days after transplanting.

               ·         Leaf blight: water soaked lesion at the tip of the leaf.

               ·         Later it leads to drying of the leaf from tip to bottom with wavy margin.

Management:

               ·         Seed treatment and foliar spray with Streptomycin sulphate - 200ppm.

               ·         Copper hydroxide – Kocide

8.   Bacterial leaf streak: Xanthomonas oryzae pv.oryzicola

Symptom

            ·       Initially water soaked streaks are formed. Later it turns to reddish brown streaks.

Management

            ·       Seed treatment and foliar spray with Streptomycin sulphate - 200ppm.

9.   Rice tungro disease: Rice tungro bacilliform virus / Rice tungro spherical virus.

Vector: Nephotetix virescens/ Nephotetix impecticeps

Symptoms

            ·       Reduced tillering and stunting of the plant. Orange yellow discoloration of leaves.

     Management

            ·       Foliar spray with systemic insecticide and 2% urea.

10.     Rice yellow dwarf: Phytoplasma Vector: Nephotetix virescens/ Nephotetix impecticeps.

Symptoms

            ·       Excessive tillering and stunting of the plant. Yellow discoloration on leaves.

      Management

            ·       Foliar spray with systemic insecticide and 2% urea.

Other important diseases:

1.   Udbatta disease: Ephelis oryzae (Sexual stage: Balansia oryzae-sativa).

2.   Narrow brown leaf spot :Cercospora janseana (Sexual stage : Sphaerulina oryzina)

3.   Stackburn disease :Trichoconis padwickii (Syn : Alternaria padwickii)

4.   Bunt or Kernel Smut or black smut : Tilletia barclayana

5.   Stem rot :Sclerotium oryzae (Sexual stage : Magnaporthe salvinii)

6.   Grassy stunt disease: Grassy stunt virus

7.   Ragged stunt disease: Ragged stunt virus

 

 

 

 

 

 

 

 

 

 

 

 

 

 

28. DISEASES OF WHEAT

1.   Black stem rust: Puccinia graminis f.sp. tritici

Symptoms

·      Seen only on the stem. Initially linear, elongated reddish brown raised pustules. Later it turns to black raised linear pustules.

2.   Brown / orange leaf rust: Puccinia graminis f.sp .recondida

Symptoms

·      Mostly seen on the leaves. Reddish brown/orange raised pustules scattered on the leaf surface. Later the orange pustules turn to black lesion.

3.   Leaf yellow stripe rust: Puccinia graminis f.sp. striformis

Symptoms

·      Mostly seen on the leaves. Yellow, linear and elongated raised stripes on the leaf surface. Later it turns to black elongated stripes.

Management

                 ·         Foliar spray with Carboxin or Oxycarboxin 0.1%

4.   Loose smut of wheat: Ustilago nuda f.sp. tritici/ Ustilago tritici

Symptoms

                 ·         Individual spikelets are converted into smut sorus (black kernals). These are easily blown off by wind leaving the rachis alone.

Management

                 ·         Luthra’s solar treatment – soak the seeds in cold water for 4 hours from 8 to 12 noon. Decent the water and dry the seeds in sunlight for four hours (12pm to 4pm) by spreading over the threshing floor.

                 ·         Foliar spray with Mancozeb 0.25%.

5.   Tundu disease / Yellow ear rot / Ear cockle disease: Clavibacter tritici associated with

nematode: Anguina tritici.

Symptoms

                        ·         Exudation of yellow, slimy liquid from individual spikelets. Oozing is deposited on the stalk of the ear head, stem as well as surface of the leaves.

Management:

                        ·         Soak the seeds in brine solution -10%, remove the floating infected grains and wash the good seed with running tap water.

                        ·         Seed treatment with streptomycin sulphate – 200ppm.

Other important diseases:

      ·         Flag smut : Urocystis tritici

      ·         Rough spored bunt or Stinking smut : Tilletia caries

      ·         Smooth spored bunt: Tilletia foetida

      ·         Karnal bunt: Neovassia indica

      ·         Foor rot: Pythium graminicolum and P. arrhenomanes

      ·         Powdery mildew: Erysiphe graminis var. tritici

 

 

 

 

 

 

 

 

 

 

 

29. DISEASES OF SORGHUM

1.   Downy mildew: Peronosclerospora sorghi

Symptom:

·      Downy mildew: White downy growth on the lower surface of the leaf. Yellow discoloration on the corresponding upper surface.

·      Leaf shredding: formation of chlorotic streaks along the veins due to oospore formation.

Management:

·      Foliar spray with Metalaxyl - 0.4%.

2.   Charcoal rot: Rhizoctonia solani / Macrophomina phaseolina

Symptom:

·      Seen only at the flowering phase when crop is subjected to moisture stress. When we split open the internal portion is fibrous and hallow with black vegetative structures namely the sclerotia and pycnidia.

Management: Frequent irrigation at the time of flowering phase.

3.   Rust disease: Puccini sorghi

Symptom:

·      Reddish brown raised pustules on the leaf surfaces.

·      Later the reddish brown pustules turn to black pustules.

Management:

·      Foliar spray with carboxin or oxycarboxin 0.1%

4.   Ergot/ sugary diseases: Claviceps purpurea

Symptoms:

·      Mostly seen when the flowering phase coincides with the winter season.

·      Characteristic honey dew secretion from individual spikelets.

Each spikelets is converted into black ergot/sclerotia.

Management:

·      Foliar spray with Mancozeb 0.25% (consumption purpose), Thiophanate methyl 0.1% (seed purpose).

Diseases / casual organism	5. Grain smut / Kernel smut / Covered smut / Short smut: Sphacelotheca sorghi	6.Loose smut / Loose kernel smut: Sphacelotheca cruenta	7.Long smut : Tolyposporium ehrenbergii	8.Head smut : Sphacelotheca reiliana
Symptom	Almost all the individual grains are smutted. Sorus is small. Externally seed borne disease	Almost all the individual grains are smutted. Externally seed borne disease.	Only 2% of grains are smutted. Air borne disease.	Entire head is converted into a single smut sorus. Soil borne disease.
Management	Seed treatment with captan/ thiram – 4g/kg of the seed.	Seed treatment with captan/ thiram – 4g/kg of the seed.	Foliar spray with mancozeb 0.25%	Seed treatment with captan/ thiram – 4g/kg of the seed.

 

Other important diseases:

1.   Anthracnose or Red leaf spot: Colletotrichum graminicolum.

2.   Leaf blight: Helminthosporium turcicum

3.   Twisted top/Bokah boeing: Fusarium moniliforme

4.   Phanerogamic parasite/Witch weed: Striga asiatica/Striga densiflora

5.   Symptom: yellowing of the entire plant. Stunted growth.

6.   Management: application of the 2,4 D

7.   Leaf spot: Cercospora sorghi

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

30. DISEASES OF PEARL MILLET

1.   Downy mildew / Green ear: Sclerospora graminicola

Symptom:

·      Downy mildew: White downy growth on the lower surface of the leaf. Yellow discoloration on the corresponding upper surface.

·      Green ear: Ear head are converted into green leaf like structure. It may be partially or fully.

Management:

·      Foliar spray with Metalaxyl 0.4%.

2.   Rust disease: Puccini penniseti

Symptom:

·      Reddish brown raised pustules on the leaf surfaces.

·      Later the reddish brown pustules turn to black pustules.

Management:

·      Foliar spray with carboxin or oxycarboxin 0.1%.

3.   Smut : Tolyposporium penicillariae

Symptom:

·      Individual grains are converted into smut spores. Numerous black smut spores are formed.

Management: foliar apray with mancozeb 0.25%

·      Ergot or Sugary disease :Claviceps fusiformis

4.   Charcoal rot: Rhizoctonia solani/ Macrophomina phaseolina

 

 

 

 

 

 

 

 

31. DISEASES OF MAIZE

1.   Downy mildew/ crazy top: Peronosclerospora sorghii

Symptom:

·      Downy mildew: White downy growth on the lower surface of the leaf. Yellow discoloration on the corresponding upper surface.

·      Crazy top: the tassels are converted into green leaf like structure which leads to tassel malformation.

Management:

·      Foliar spray with Metalaxyl 0.4%.

2.   Rust disease: Puccini sorghi

3.   Charcoal rot: Rhizoctonia solani/ Macrophomina phaseolina

4.   Head smut :Sphacelotheca reiliana

 

 

 

 

 

 

 

 

 

 

 

 

32. DISEASES OF REDGRAM

1.   Wilt: Fusarium oxysporum fsp.udum.

Symptom:

·      Yellowing and drooping of the plants.

·      Partial wilting or entire wilting of the plant is seen.

·      Pink discoloration in the vascular region is the characteristic symptom.

Management:

·      Spot soil drenching with copper oxychloride @0.25%.

2.   Dry root rot: Macrophomina phaseolina/ Rhizoctonia bataticola

Symptoms:

·      Yellowing of the plant.

·      Drying and wilting of the whole plant.

·      Typical bark shedding is seen.

Management:

·      Frequent irrigation at the time of flowering phase.

3.   Wet root rot: Rhizoctonia solani/ Thanatephorus cucumeris

Symptoms:

·      Reddish brown lesion at the collar region. This leads to girdling of the basal stem.

·      External symptom is yellowing of the plant.

Management:

·      Spot soil drenching with copper oxychloride @0.25%.

4.   Powdery mildew: Leveillula taurica

Symptom:

·      White powdery growth on the lower surface of the leaf.

·      On the corresponding upper surface yellow discoloration of the leaves is seen.

Management:

·      Foliar spray with Wettable powder-0.25%, dinocap – 0.05%, tridemorph- 0.1%.

5.   Sterility mosaic: Pigeon pea sterility mosaic virus. Vector: Aceria cajani

Symptom:

·      Reduction of leaf size and proliferation of auxillary buds.

·      Sterility of the plant is also observed.

Management:

·      Spraying of dicofol-0.1%, inorganic sulphur.

6.   Yellow mosaic: Pigeon pea yellow mosaic virus.

Symptom: plants become stunted and on the leaves alternate patches of yellow and green discoloration is observed.

Management:

·      Destruction of the infected plants and foliar spray with systemic insecticide.

 

 

 

 

 

 

 

 

 

 

 

 

 

33. DISEASES OF BLACKGRAM AND GREENGRAM

1.   Powdery mildew: Erysiphe polygoni

Symptom:

·      White powdery growth on the upper surface of the leaf.

·      In severe case it leads to drying of the leaves.

Management:

·      Foliar spray with Wettable Sulphur - 0.25%, Dinocap – 0.05%, tridemorph- 0.1%.

2.   Rust disease: Uromyces phaseoli

Symptom

·      Reddish brown raised pustules on the leaf surfaces.

·      Later the reddish brown pustules turn to black pustules.

Management:

·      Foliar spray with carboxin or oxycarboxin 0.1%.

3.   Leaf spot: Cercospora canescens

Symptom: Circular spots on the leaves with reddish brown margin and grey centre.

Management: Foliar spray with chlorothalonil - 0.25%.

4.   Leaf crinkle: Blackgram leaf crinkle virus. Vector: Bemisia tabaci

Symptom:

·      Crinkling of the leaves, thickening of the interveinal area.

·      Stunting of the plant.

Management:

·      Destruction of the infected plants and foliar spray with systemic insecticide.

5.   Yellow mosaic: Mungbean yellow mosaic virus Vector: Bemisia tabaci

Symptom:

·      Mosaic mottling of the leaves with alternate green and yellow patches.

·      Stunting of the plant.

Management:

·      Destruction of the infected plants and foliar spray with systemic insecticide.

6.   Dry root rot: Macrophomina phaseolina/ Rhizoctonia bataticola

7.   Wet root rot: Rhizoctonia solani/ Thanatephorus cucumeris

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

34. DISEASES OF BENGALGRAM / CHICKPEA

1.   Wilt: Fusarium oxysporum f.sp.ciceri

2.   Dry root rot: Macrophomina phaseolina/ Rhizoctonia bataticola

3.   Wet root rot: Rhizoctonia solani/ Thanatephorus cucumeris

4.   Rust disease: Uromyces ciceris arietini

5.   Aschochyta blight: Ascochyta rabiei

Symptoms:

·      On the leaves water soaked lesions seen, which later develop into round spot with brown margin and grey centre. The symptom spreads to the stem and fruits.

·      Spots on the stem lead to girdling of the stem.

·      Spots on the leaves and fruits coalesce and lead to blighting symptom.

Management:

·      Foliar spray with Tridemorph-0.1%, copper oxy chloride -0.25%, mancozeb -0.25%

COWPEA, LAB LAB, PEAS

1.   Anthracnose: Colletotrichum lindemuthianum

Symptoms:

·      On the pods initially water soaked lesion appear.

·      Later it turns to brown and enlarge into circular spots.

·      Spots are depressed at the centre with reddish brown margin and black centre.

Management:

·      Foliar spray with Tridemorph-0.1%, copper oxy chloride -0.25%, mancozeb -0.25%

2.   Downy mildew of peas: Pernospora pisi

3.   Dry root rot: Macrophomina phaseolina/ Rhizoctonia bataticola

4.   Wet root rot: Rhizoctonia solani/ Thanatephorus cucumeris

5.   Aphid borne mosaic: Cowpea aphid-borne mosaic virus

Symptom:

·      Mosaic mottling of the leaves with alternate dark green and light patches.

·      Stunting of the plant.

Management:

·      Destruction of the infected plants and foliar spray with systemic insecticide.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

35. DISEASES OF GROUNDNUT

1.   Dry root rot: Macrophomina phaseolina/ Rhizoctonia bataticola.

2.   Wet root rot: Rhizoctonia solani/ Thanatephorus cucumeris

3.   Crown rot: Aspergillus flavus

Symptom:

·      Pre emergence: Rotting of the seeds before the emergence of the seedling.

·      Post emergence: Rotting at the collar region of the seedling.

·      Crown rot: On the well-established plant, rotting at the basal portion and spreads upward and leads to death of the entire plant.

Management:

·      Shallow sowing of the seeds and adopt wider spacing.

·      Spot soil drenching with copperoxychloride.

4.   Tikka disease: Cercospora arachidicola (early leaf spot) & Cercospora personata (late leaf spot)

Symptom:

·      Early tikka leaf spot: seen within 3-4 weeks of sowing. On the leaves irregular to circular reddish brown/ black lesions surrounded by “yellow halo”

·      Late tikka leaf spot: seen within 5-7 weeks of sowing. Mostly on the leaf margin, enlarged black lesion without yellow halo.

Management:

·      Foliar spray with chlorothalonil -0.25%.

5.   Rust disease: Puccinia arachidis

6.   Rosetting: Groundnut rosette virus

Vector: Aphis craccivora

Symptom:

·      Mosaic mottling of the leaves with alternate dark green and light patches.

·      Stunting of the plant.

·      Bushy appearance due to the proliferation of the auxillary buds.

Management:

·      Destruction of the infected plants and foliar spray with systemic insecticide.

7.   Bud necrosis: Tomato spotted wilt virus

Vector: Thrips tabaci

Symptom:

·      Necrotic symptom on the terminal portion of the leaf.

·      Stunting of the plant.

·      Bushy appearance due to the proliferation of the auxillary buds.

Management:

·      Destruction of the infected plants and foliar spray with systemic insecticide.

 

 

 

 

 

 

 

 

 

 

 

 

36. DISEASES OF SESAME AND SUNFLOWER

SESAME

1.   Wilt: Fusarium oxysporum fsp. Sesami

2.   Powdery mildew: Erysiphe cichoracearum

3.   Leaf spot: Cercospora sesami

4.   Leaf blight: Alternaria sesami

5.   Dry root rot: Macrophomina phaseolina/ Rhizoctonia bataticola

6.   Wet root rot: Rhizoctonia solani/ Thanatephorus cucumeris

7.   Sesamum phyllody: Phytoplasma

Vector: Orosius albicinctus

Symptom:

·      Formation of the phylloid flowers.

·      All the floral parts are converted into green leaf like structure.

Management:

·      Foliar spray with tetracycline – 100ppm.

·      Foliar spray with systemic insecticides from two-leaf stage.

 

SUNFLOWER

1.   Head rot: Rhizopus nigricans

Symptom:

·      Irregular water soaked lesion is seen on the backside of the head portion.

·      Lesion turns to black and spread to entire head and leads to rotting of the head.

Management:

·      Foliar spray with mancozeb -0.25%, calixin -0.1%

2.   Rust: Puccinia helianthi

3.   Leaf blight: Alternaria helianthi

4.   Dry root rot: Macrophomina phaseolina/ Rhizoctonia bataticola

5.   Wet root rot: Rhizoctonia solani/ Thanatephorus cucumeris

6.   Powdery mildew: Erysiphe cichoracearum

7.   Sunflower necrosis: Tobacco streak virus

Vector: Thrips tabacci

Symptom:

·      Stunting of the plant.

·      Necrotic lesion is seen on the veins, petioles and the stem.

·      Malformation of the flower.

Management:

·      Destruction of the infected plants and foliar spray with systemic insecticide.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

37. DISEASES OF COCONUT AND CASTOR

COCONUT

1.   Basal stem end rot: Ganoderma lucidum

Symptom:

·      Reddish brown oozing from the base of the stem and spreads upward.

·      Drooping of the lower fronds.

·      Oozing is through the cracks.

·      Formation of sexual fruiting body – basidiocarp.

Management:

Curative:

·      Isolation trench : apply sufficient amount of sulphur dust inside the trench.

·      Soil drenching : Bordeaux mixture – 1% @40 litres/ tree.

·      Trunk injection: Calixin @ 3ml/ trunk, 4 injections @ 4 month interval.

·      Root feeding : Calixin @ 3ml + 100ml water.

2.   Kerala wilt: Phytoplasma

Symptom:

·      Production of the small fronds.

·      Fronds became pale yellow in color.

·      Ribbing and flaccidity of the fronds.

·      No decay of roots and rootlets.

Management:

·      Remove the plant and burn it.

3.   Stem bleeding of coconut: Ceratocystis paradoxa

Symptom:

·      Reddish brown oozing through the cracks @ any parts of the trunks. External symptom only.

Management:

·      Scrap the bleeding patches and sterilize the scrapped portion with fire.

·      Swab the Bordeaux paste 10% on the sterilized surface.

4.   Cracking and malformation: Botrydiploidia theobromae

Symptom:

·      Malformation of the coconut

·      Splitting of the exocarp. Hardiness of the coconut.

·      Nut fall is commonly seen.

Management:

·      Crown clearing: Removal of infected plant parts.

·      Trunk injection – Calixin - 3ml

5.   Bud rot of coconut: Phytophthora palmivora

Symptom:

·      Pale yellow discoloration of the heartleaf. Withering of the heartleaf.

·      Infected leaves can be easily pulled out.

·      At the base of the fronds reddish brown rotting is seen.

Management:

·      Foliar spray and trunk injection with fosetyl aluminium – 0.1%

6.   Grey blight : Pestalotia palmarum

Symptom:

·      Irregular/ circular shaped lesions with brown margin and grey centre.

Management:

·      Foliar spray with copper oxychloride.

·      Trunk injection with calixin.

7.   Lethal yellowing: Phytoplasma

Symptom:

·      Stunting and yellowing of the plant.

·      Reduction of leaf size.

Management:

·      Destruction of the infected plants and foliar spray with systemic insecticide.

CASTOR

1.   Seedling blight: Phytophthora parasitica

Symptom:

·      Irregular water soaked lesion on the leaves.

·      Later it turns to black color and it spreads to petiole and stem.

Management:

·      Foliar spray with fosetyl aluminium -0.1%

2.   Dry root rot: Macrophomina phaseolina/ Rhizoctonia bataticola

3.   Wet root rot: Rhizoctonia solani/ Thanatephorus cucumeris

4.   Rust disease: Melampsora ricini

5.   Leaf blight: Alternaria ricini

6.   Leaf spot: Cercospora ricini

 

 

 

 

 

 

 

 

 

 

 

38. DISEASES OF SUGARCANE

1.   Damping off: Pythium aphanidermatum

Symptom:

·      Pre emergence: before the emergence of the seedling. Death of the sets occurs inside the soil itself.

·      Post emergence: after the establishment of the seedling. Reddish brown lesion at the collar region of the seedlings is seen.

Management:

·      Spot soil drenching with copperoxychloride -0.25%.

2.   Redroot of sugarcane: Colletotrichum falcatum

Symptom:

·      Shrinkage of the cane.

·      Yellowing and drying of leaves in patches.

·      Reddish brown discoloration interrupted with white patches of fungal growth.

·      On the leaves reddening of midrib is also seen.

Management:

·      Set treatment with carbendazim -0.1%

·      Foliar spray with tridemorph – 0.1%

3.   Wilt: Cephalosporium sacchari

Symptom:

·      Stunting, yellowing of crown leaves.

·      Midrib of the leaves turn yellow white leaf lamina remains green.

·      Reddening of internal tissues without any white patches.

·      Infected canes emit foul smell.

Management:

·      Set treatment with carbendazim -0.1%

·      Foliar spray with tridemorph – 0.1%

4.   Set rot/ pineapple disease: Ceratocystis paradoxa

Symptom:

·      Reddening of internal tissues without any white patches.

·      Infected cane emits pineapple odour.

·      Internodes become hollow and black in color.

Management:

·      Set treatment with carbendazim -0.1%

·      Soil drenching with coc-0.25%

5.   Whip smut: Ustilago scitaminea

Symptom:

·      Severe infection is seen in ratoon crop.

·      Central shoot is converted into single whip like smut spores.

Management:

·      Foliar spray with carboxin/oxycrboxin -0.1%

6.   Rust: Puccinia melanocephala

7.   Eyespot: Helminthosporium sacchari

8.   Ratoon stunting disease: Clavibacter xyli pv. xyli

9.   Sugarcane mosaic: Sugarcane mosaic virus

Vector:Melanaphis sacchari

10.                 Grassy shoot disease: Phytoplasma

Vector: Aphis sacchari

 

 

 

 

 

 

 

 

39. DISEASES OF COTTON

1.   Wilt diseases: Fusarium oxysporum f.sp. Vasinfectum

2.   Verticillium wilt: Verticilium dahliae

Symptom:

·      Infected stem and roots show dark brown discoloration if we split open the stem.

·      On the leaves tiger stripe symptom is seen. Veins turn brown and interveinal areas become chlorotic.

·      Cupping of leaf and tissues b/w the veins dry in patches.

Management:

·      Spot soil drenching with copperoxychloride -0.25%

3.   Black arm of cotton: Xanthomonas axonopodis pv.malvacearum

Symptom:

·      Seedling blight: Watersoaked lesions on the cotyledon leaves.

·      Angular leaf spot: On mature plants, water soaked spots on the leaves restricted in b/w the vein and veinlets.

·      Vein blight: Angular spots in leaf lamina extend to the vein and veinlets. The vein and veinlets become black and blighted.

·      Black arm: Blackening extends from veins to the sympodial branches leaving the plant as bare resembles like black arm.

·      Boll rot: On the boll depressed, circular, reddish brown lesion is seen.

Management:

·      Spot soil drenching with copperoxychloride -0.25%.

·      Foliar spray with streptomycin sulphate- 200pm.

4.   Areolate mildew/ grey mildew: Ramularia areola

Symptom:

·      Frosty white to grey mildew patches appear on the under surface of the leaf.

Management:

·      Foliar spray with calixin-0.1%.

5.   Leaf blight: Alternaria macrospora

6.   Leaf spot: Cercospora gossypina

7.   Rust disease: Phakopsora gossyii

8.   Anthracnose: Colletotrichum capsici

9.   Stenosis: Phytoplasma

Vector: Unknown.

Symptom:

·      Rosetting of plant and reduction of leaf size.

Management:

·      Destruction of the infected plants and foliar spray with systemic insecticide

 

 

 

 

 

 

 

 

 

 

 

 

 

40. DISEASES OF TOBACCO

1.   Damping off: Pythium aphanidermatum

2.   Black shank: Phytophthora parasitica var nicotianae

Symptom:

·      Black lesion is seen at the collar region which spreads both upward and downward.

·      Later it leads to girdling symptom.

Management:

·      Foliar spray with fosetyl aluminium -0.1%

3.   Frog eye spot: Cercospora nicotianae

Symptom:

·      Reddish brown spots with grey centre and look similar to that of frog’s eye.

Management:

·      Foliar spray with mancozeb -0.25%

4.   Powdery mildew : Erysiphe cichoracearum var. nicotianae

5.   Wild fire: Pseudomonas tabaci

Symptom:

·      Symptom is seen on the leaves, stem and twigs.

·      Initially water soaked lesions is seen on the above said parts, which later turns to drying of the leaves.

·      This gives a wild fire like appearance.

Management:

·      Foliar spray with streptomycin sulphate – 200ppm

6.   Tobacco mosaic: Tobacco Mosaic Virus (TMV)

Symptom:

·      Stunting of the plant.

·      Reduction of the leaf size.

·      Mosaic mottling with alternate patches of green and yello colour.

·      Malformation of the leaf.

7.   Leaf curl : Tobacco leaf curl virus

8.   Phanerogamic parasite/ broom rape: Orobanche cernua var. desertorum

9.   Anthracnose: Colletotrichum tabacum

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

41. DISEASES OF BANANA

1.   Panama disease – Fusarium oxysporumf.sp. cubense

Symptoms

Symptoms appears only after 6 months of transplanting

·      Spliting of pseudostem @ the base near soil level

·      Cross section of the corm shows – vascular discoloration (Reddish brown streak around the

periphery of center of the corm

·      If we split open the infected rootlets – pinkish discoloation is seen due to nematode

Management

·      Pairing & prolinage before plant for elimation of nematode damage

·      Sprinkle wthcarbofuran @20g/corm on surface before planting

·      Corm injection – with 2% carbendazim – 3ml / corm @ 6th and 7th month

·      Capsule application with carbendazim

2.   Sigatoka disease – Mycosphaerella musicola

Symptoms

·      Spindle shaped lesions characterized by dark brown margin & grayish centre

·      It is surrounded by yellow halo and later they coalesce and cause drying

Management

·      Foliar spray – Chlorothalonil – 0.25%

3.   Anthracnose – Colletotrichum musae

Symptoms

·      Initially circular reddish brown spots on surface fruit surface turns to irregular black lesion with acervuli leads to rotting of fruits

4.   Cigar end rot – Verticillium theobromae

Symptoms

·      Tip of fruit are turned to ash colored with malformation end resembles like burnt cigar

5.   Moko disease – Burkholderia solanacearum

Symptoms

·      Cavendish group of banana highly susceptible

·      Seen @ all stages of crop

·      Side suckers & main plants show wilting

6.   Tip over disease / Erwinia rot – Erwinia caratovora

Symptoms

·      In both nursery and main field drying and wilting of plants is seen

·      At the base of the pseudostem rotting is seen

·      By giving slight pressure pseudostem will fall leaving corm inside

7.   Bunchy top disease – Banana bunchy top virus (Vector: Pentalonianigronervosa)

Symptoms

·      Stunting of plants, bunching of terminal leaves gives resette appearance

·      Dark green streaks on petiole, midrib and leaf lamina

·      Green leaf like structure is seen at the tip of bract

8.   Bract mosaic / Kokkan disease – Banana bract mosaic virus

9.   Banana streak Disease – Banana streak virus

Vector: Aphis gossypii

10.                 Minor disease

·      Freckle – Phyllostictina musarum

·      Crown rot – Botrydiplodia theobromae

 

 

42. DISEASES OF MANGO

1.   Malformation – Fusarium moniliforme var. subglutinans

·      Symptoms – Vegetative malformation – Bunchy top symptom

·      Floral malformation – produce huge number of flowers gives bushy appearance

2.   Powdery mildew – Oidium mangiferae

·      Symptoms – White podery growth on leaves, Tender shoots, floral parts, Fruits

3.   Anthracnose – Gloeosporium gloeosporioides

Symptoms – Leaf spot – Circular, Reddish brown spot on leaf surface

          Die back – Dieing of twigs from tip to downwards

          Floral blight – blackening of floral axis

          Fruit – Irregular black lesion o fruit leads to rotting

4.   Die back – Botrydiplodia theobromae

5.   Sooty mould – Capnodium ramosum

6.   Grey blight – Pestalotiopsis mangiferae

7.   Red rust – Cephaleuros virescens

8.   Bacterial canker – Xanthomonas campestris pv. mangiferae-indica

9.   Giant mistletoe – Dendropthe sp.

10.                 Bacterial leaf spot – Pseudomonas mangiferae-indicae

 

 

 

 

 

 

43. DISASES OF CITRUS

1.   Gummosis, leaf fall and fruit rot – Phytophthora spp.

2.   Diplodia gummosis – Diplodia natalensis   

3.   Ganoderma root rot – Ganoderma lucidum

4.   Anthracnose – Colletotrichum gloeosporioides

5.   Citrus canker – Xanthomonas axonopodis pv. citri

Symptoms

·      On leaves: Small yellowish spots on leaves – spots swell and raised above the surface asbrown corky outgrowth of spongy eruption – spots surrounded by yellow halo.

·      On twigs: irregular raised cankers on the surface resulting in drying

·      On fruits: round to irregular raised cankerous growth on the surface.

6.   Cirus greening – Candidatusliberobacter (Fastidious phloem limiting bacteria)

Symptoms

·      Reduced foliage with severe die back of twigs

·      Fruits fails to ripen and remain green imparts unpleasant flavour to juice

7.   Tristeza – Citrus tristeza virus

Symptoms

·      Vein flecking seen on leaves

·      Severe stem pitting is seen

·      Die back of entire tree

8.   Exocortis – Citrus exocortis viroid

9.   Fruit rots

i.     Blue & Green mould – Penicillium spp

ii.   Alternaria rot – Alternaria citri

iii. Soft rot – Aspergillus niger

iv. Sour rot – Geotrichumcandidum

10.   Red rust – Cephaleuros virescens

 

 

 

 

44. DISEASES OF GRAPES

1.   Powdery mildew – Uncinulanecator

Symptoms

·      Occurs on all stages of crops

·      White powdery growth on the upper surface of leaves, tender shoots, tendrils, floral parts and immature fruits

·      Infected leaves dried and fall off

2.   Downy mildew – Plasmopara viticola

Symptoms

·      Occurs on all stages of crops

·      White downy growth on lower surface of leaves and corresponding to upper surface yellow discoloration is seen

·      Infection on fruits shows downy growth and fruit splitting is also seen

·      Infected leaf dried off and stick to plant itself

3.   Anthracnose (Bird’s eye spot) – Elsinoe ampelina

Symptoms

·      Fruits – Depressed, circular, brown spot on fruit surface resembling bird’s eye with grey

·      Centre Laves – Dark brown spot with grey centre surrounded by yellow halo

·      Stem – Black elliptical sunken lesions on young shoots cause girdling & death

4.   Fruit rot

·      Grey mould – Botrytis cinerea

·      Blue mould – Penicillium digitatum

·      Soft rot – Phomopsis viticola

·      Stalk end rot – Aspergillus niger

·      Penicillium rot – Penicillium canescens

·      Rhizopus rot – Rhizopus nigricans

5.   Fan leaf – Grapevine fan leaf virus (Vector: Xiphinema index)

6.   Leaf roll – Grapevine leaf roll associated virus (Vector: Mealy bug)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

45. DISEASE OF GUAVA, SAPOTA, PAPAYA

GUAVA

1.   Wilt – Fusarium oxysporum f.sp. psidii

2.   Fruit canker / Scab / Grey blight – Pestalotiopsis psidii

Symptoms

·      Infected green fruits has small, brown colord, unbroken, circular scabby raised lesions

3.   Anthracnose – Gloeosporium psidii

4.   Red rust – Cephaleuros virescens

5.   Fruit rot – Phomopsis psidii

SAPOTA

1.   Leaf spot – Phavophloeospora indica

2.   Sooty mould – Capnodium sp.

3.   Flat limb – Botryodiplodia theobromae

PAPAYA

1.   Stem rot / Foot rot – Pythium aphanidermatum and Rhizoctonia solani

Symptoms

·      On mature plants, show complete decay of basal portion of the stem

·      Fruits shriveled and drop off

2.   Powdery mildew – Oidium caricae

3.   Anthracnose – Colletotrichum papaya

4.   Leaf spots – Cercospora papaya

5.   Ring spot – Papaya ring spot virus

Symptoms

·      Leaves – Circular, chlorotic ring spot is seen

·      Severely infected leaves become linear & thread like showing shoe string / Rat tail symptom

·      Fruits – Chloroticringspot is seen on fruit surface with concentric rings

·      On petiole & stem of the plant having linear oil streaks

46. DISEASES OF POMEGRANATE AND PINE APPLE

POMEGRANATE

1.   Bacterial blight – Xanthomonas axonopodis pv. punicae

Symptoms

·      Small irregular water soaked spots on the leaves

·      Later becomes necrotic and angular – leaves dried and fall off

Management – Bordeaux mixture – 1%

2.   Cercospora leaf spot – Cecospora punicae

3.   Leaf spots – Colletotrichum gloeosporioides

4.   Cladosporium fruit rot – Cladosporium oxysporum

5.   Aspergillus fruit rot – Aspergillus spp.

6.   Mild soft rot – Penicillium chrysogenum

7.   Soft rot – Rhizopus arrhizus & R. stolonifer

8.   Phomopsis rot – Phomopsis sp.

PINEAPPLE

9.   Heart rot / Stem rot / Root rot – Phytophthora cinnamomi; P. parasitica

Symptoms

·      Affected leaves turn yellowish green and became brown

·      Inner whorl of leaves can be easily detached by slight pull

·      Fruit development arrested and entire plant wilts

·      Root also change in to black color

Management

·      Crown drenching with COC – 0.25%

·      Foliar spray – Fosetyl Aluminium – 0.1%

10.                 Base rot / Fruit rot and Leaf spot – Ceratocystis paradoxa

Symptoms

·      Tissues in the butt are destroyed followed by wilting

·      Diseased plants break off at ground level

·      On leaves – Spots seen with dark brown margin and grey centre

·      On fruits – Water soaked lesions turn to yellow and then tissues become soft, rotten and emit foul smell

11.                 Wilt – Pineapple wilt virus

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

47. DISEASES OF APPLE AND PEACH

APPLE

1.   Apple scab – Venturia inaequalis

·      Symptoms – Scattered, rough, Circular, brown spots appear on leaves and they may be slightly raised

·      On fruits – Small, rough, black, circular lesions on their skin and they enlarge and then depress leading to shrinkage

2.   Powdery mildew – Podosphaera leucotricha

Symptoms

·      All parts of tree are affected. Small grayish or white patches of fungal growth appear.

·      Affected leaves become crinkled, curled and the entire surface of leaf is covered with fungus.

·      On fruits causes depression andaffected fruits harden and develop cracks.

3.   Fire blight – Erwinia amylovora

Symptoms

·      Infected flowers, leaves and twigs become water soaked, shrivel, turn brown to blackish and fall or remain hanging in the tree.

·      Infected fruits mummified and finally turn black and clinging to tree

4.   Crown gall – Agrobacterium tumefaciens

Symptoms

·      Hard and corky galls appear on the stem and roots at the crown region and infected plants are stunted and chlorotic.

5.   Fruit rots

                                              i.     Brown rot – Sclerotiniafructigena

                                           ii.     Soft rot – Penicilliumexpansum

                                         iii.     Bitter rot – Glomerellacingulata

                                          iv.     Whisker’s rot – Rhizopusarrhizus

                                            v.     Pink mould – Trichotheciumroseum

                                          vi.     Core rot – Alternariaalternata

PEACH

6.   Leaf curl – Taphrina deformans

Symptoms

·      Leaf blade thickness and curls. Affected portion becomes yellow and finally to reddish purple. This area is converted with a whitish grey bloom of the fungus on the upper surface. Affected leaves exhibit drying.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

48. DISEASES OF VEGETABLES

TOMATO

1.   Damping off – Pythium aphanidermatum

·      Seedlings are affected.

·      Brown discolouration at the lower portion of stem.

·      Seedlings become weak and collapse.

2.   Early blight – Alternaria solani

·      Symptoms are observed on leaves, stem and fruits.

·      Brown, necrotic and irregular with concentric zones on leaf

·      On stem brown discoloration leads to girdling.

3.   Wilt – Fusarium oxysporium f. sp. lycopersici

·      Affected plants exhibits yellowing of lower leaves

·      Internal stem portion exhibits, vascular browning.

4.   Leaf curl - Tobacco leaf curl virus (Vector – Whitefly – Bemissia tabaci)

5.   Spotted wilt – Tomato spotted wilt virus - Thrips

·      Necrotic irregular spots are visible on the surface of leaf with green centre.

·      Leaf exhibits bronzing.

·      On fruit, pale yellow patches are scattered on the surface.

6.   Septoria leaf spot - Septoria lycopersici

BHENDI

1.   Powdery mildew – Erysiphe cichoracearum

2.   Cercospora leaf spot – Cercospora malayensis

3.   Yellow vein mosaic - Yellow Vein Mosaic Virus

                        ·         Main and lateral veins are bleached.

                        ·         Interveinal portion exhibits green color later bleached off.

BRINJAL

1.   Alternaria leaf spot - Alternaria melongena

2.   Cercospora leaf spot – Cercospora melongena

3.   Little leaf - Phytoplasma Vector - Jassids - Cestius phycitis. (Hishimonas phycitis)

CUCURBITS

1.   Anthracnose – Colletotrichum lagenarium

2.   Downy mildew – Pseudoperonospora cubensis.

                        ·         White patch of downy growth on undersurface of leaf.

                        ·         Upper surface correspondingly shows yellow patches.

                        ·         Leads to drying of leaves.

3.   Powdery mildew - Erysiphe cichoracearum

                        ·         Whites powdery growth on the upper surface of leaf.

                        ·         Leaf exhibit drying.

4.   Cercospora leaf spot - Cercospora citrunella

5.   Mosaic - Cucumis virus 1 (Vector: Aphids)

CHILLIES

1.   Damping off – Pythium aphanidermatum

2.   Die back and fruit rot - Colletotrichum capsici

                        ·         Symptoms are seen on stem and fruit – stem shows die back symptoms.

                        ·         Water soaked spots are seen on mature fruits - Affected portion turns white.

                        ·         Acervuli are formed on the spots and seen as black dots in large numbers.

3.   Alternaria leaf and fruit spot – Alternaria solani

4.   Cercospora leaf spot – Cercospora capsici

5.   Powdery mildew – Leveillula taurica

6.   Wilt – Fusarium oxysporium f.sp.vesicatoria

7.   Chilli mosaic – Chilli mosaic virus

CRUCIFERS

1.   Club root of cabbage – Plasmodiophora brassicae

Symptom

·      External symptom: Yellowing, wilting and stunting of the plant.

·      Internal symptom: Club like swelling of root and rootlets due to hypertrophy and hyperplasia.

Management

·      Lime application at the rate of 2.5t/ha.

·      Soil drenching with pentachloronitrobenzene.

2.   Black leaf spot – Alternaria brassicae

3.   White rust – Albugo candida

4.   Downy mildew - Peronospora parasitica

ONION

1.   Purple blotch / leaf blotch - Alternaria porri

2.   Root rot – Pythium aphanidermatum; P. ultimum and P. debaryanum

BEANS

1.   Anthracnose – Colletotrichum lindemuthianum

2.   Powdery mildew – Erysiphe polygoni

3.   Rust – Uromyces appendiculatus

4.   Cercospora leaf spot – Cercospora cruenta

5.   Mosaic - Been yellow mosaic virus (Vector: White fly - Bemisia tabaci)

6.   Collar rot and Root rot – Rhizoctonia solani

PEAS

1.   Powdery mildew – Erysiphe polygoni

2.   Dowby mildew – Pernospora pisi

3.   Leaf blight – Ascochyta pisi

4.   Fusarial wilt – Fusarium oxysporium f.sp. pisi

5.   Dry root rot – Macrophomina phaseolina

SWEET POTATO

1.   White rust – Albugo ipomoeae – panduranae

2.   Soft rot – Rhizopus stolonifer

3.   Cercospora leaf spot – Cercospora ipomoeae

ARECANUT

1.   Fruit rot – Phytophthora palmivora

Symptom

·      Watersoaked lesions near the petiole. Later it turns to black and it covers the entire fruit and leads to rotting of the fruit.

Management:

                        ·         Fosetyl aluminium – 0.1%

2.   Foot rot – Ganoderma lucidum

BEET ROOT

1.   Cercospora leaf spot - Cercospora bataticola

2.   Powdery mildew - Erysiphe polygoni

TURMERIC

1.   Leaf spot - Colletotrichum capsici

Symptom

                        ·         Elongated irregular lesions with brown margin and grey centre with acervulli.

2.   Leaf blotch – Taphrina maculans

Symptom

                        ·         Irregular reddish brown lesions formed in between the vein and veinlets.

3.   Rhizome rot – Pythium graminicolum

Symptom

                        ·         Rotting of the rhizome under the soil. Finally leads to the death of the plant.

GINGER

1.   Rhizome rot / soft rot – Pythium spp.

2.   Leaf spot - Phyllosticta zingiberi

POTATO

1.   Early blight - Alternaria solani

2.   Late blight - Phytophtor ainfestans

Symptom

                        ·         Irregular black lesions seen on the leaf tip and margin.

                        ·         Later spreads to whole parts of the plant and leads to death of the plant and rottingof the tuber

Management:

                        ·         Fosetyl aluminium – 0.1%

3.   Common scab - Streptomyces scabies

Symptom

                        ·         Scabby out growth on the surface of the tubers

4.   Black scurf – Rhizoctoniasolani

Symptom

                        ·         Brown, sunken, circular or elongated lesions on the lower portion of sproutsand girdling of infected stem

                        ·         Black irregular sclerotic are found in skin of tubers with brown discoloration

5.   Brown rot – Pseudomonas solanacearum

Symptom:

                        ·         Sudden wilting of the crop.

                        ·         Vascular browning is seen on the infected tube.

                        ·         It is also associated with bacterial ooze out.

6.   Mosaic – PVY, Vein banding virus

COFFEE

1.   Rust – Hemilia vastatrix

Symptom

                        ·         Orange or yellow raised pustules seen on the lower surface of the leaf.

Management

Ø Carboxin, Oxycarboxxin, Bordeaux mixture (0.5%)

2.   Anthracnose - Colletotrichum coffeeanum

3.   Brown eyespot – Cercospora coffeeanum

4.   Sooty mould – Capnodium sp.

TEA

1.   Blister blight – Exobasidium vexans

Symptoms

                        ·         Depression on the upper surface of leaf

                        ·         Bulging on lower surface covered with myceial growth

                        ·         On stem – Blisters are seen showing craking symptoms

Management

                        ·         Foliar spray – COC – 0.25% + Nickel Chloride – 0.1%