Introduction to plant pathogens
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The document outlines the historical development of plant pathology and mycology, detailing key figures, their contributions, and significant discoveries from the 17th century to the 20th century. It highlights milestones such as the introduction of concepts like phytoalexins, the identification of diseases caused by various pathogens, and the evolution of techniques in plant disease management. Notable individuals include Anton van Leeuwenhoek, Heinrich Anton de Bary, and Norman Borlaug, among others, who have shaped the fields of plant pathology and microbial science.
Introduction to plant pathogens
- 1. Prepared by N. HIMA SHANKAR REDDY M.Sc., Plant Pathology Annamalai University INTRODUCTION TO PLANT PATHOGENS HISTORY OF PLANT PATHOLOGY 1676 -Antonvon leeuwenhoek (Dutch 1632-1729)- Developed the 1st microscope (some books mentioned the years 1675,1676,1679) 1st 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 1st 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.
- 2. 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 1st president of the “Indian Phytopathological Society” (IPS) in 1948. Reported the 1st plant viral diseases in India (Sugarcane mosaic virus) 1874- 1943 – Edwin John Butler (Ireland)- 1st 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)
- 3. The 1st 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) 1966 – Von Schmeling and Marshal Kulka – Discovered the 1st systemic fungicide (Carboxin)
- 4. HISTORY OF PLANT PATHOLOGY IN INDIA 1885 - K R Kirtikar – First Indian scientist who collected and identified fungi 1886-1971 – JF Dastur - First Indian plant pathologist, internationally known for the establishment of genus Phytophthora and diseases caused by castor (Phytophthora parasitica) and potato 1st president of the “ Indian Phytopathological Society” (IPS) in 1948 1914 - 1999 – M. J. Thirumalachur – He was known for the development of antifungal antibiotics such as Aureofungin, Written a Book “ Antibiotics in Plant disease control ” 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 Advocated the family Phytobacteriacae with seven genera viz., xathomonas, Phytobacterium, Aplanobacter, Corynebacterium, Agrobacterium, Erwinia and plectobacterium to include all pathogenic bacteria. Y.L. Nene- Reported khira disease of rice is due to ‘Zinc’ deficiency Authored the book “ Fungicides in plant disease control” (Y. L. Nene & P. N. Thapliyal) and “The pigeon pea” 1892-1950 - K. C. Mehta – Considered as “Father of Indian Rust” Studied epidemiology of cereal rust in india Wrote monograph on “Further studies on cereal rust in India” 1896 -1952 – B. B. Mundukar Established Indian Phytopathological society with the Journal “ Indian phytopathology” Wrote “ Fungi and Plant Diseases” in 1949 ‘Monograph on Ustilaginales of india’ and the ‘Supplements to fungi of india’ and Gerena of rusts in collaboration with M. J. Thirumalachur. 1975 – S. Nagarajan and H. Singh – Formulated “Indian Stem Rust Rules” for Puccinia graminis tritici 1978 – S. Nagarajan and Joshi – Identified Puccinia pathway
- 5. BACTERIA Ehrenberg (1829) – Coined the term “Bacteria” 1675 – Leeuwenhoek – Developed 1st 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 1st 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 4th 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".
- 6. Wrote the 1st 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)
- 7. VIROLOGY Virus :- Plant viruses are sub-microscopic, infectious, obligate intracellular parasites, which do not replicate without a living host. Virus is derived from Latin word which means - Poison/ Venom/Slimy liquid Study of Plant viruses and virus like pathogens is called – Plant Virology HISTORY:- 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. 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. 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 1915 – Twort, 1917 -F. D. Herelle – Individually discovered bacteriophages 1929 – Mckinney – Developed cross protection/ pre-immunization technique for control of citrus tristeza virus (CTV) Cross protection was 1st used against TMV 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 ‘A virus is a virus’. It is neither a living organism nor a non-living chemical, but something between and betwixt Andrew Lwoff
- 8. Molecular plant pathology work can be initiated with W. M. Stanley 1936 – F. E. Bawden and N. W. Pirie – Demonstrated that virus is a nucleoprotein which consists both nucleic acid and protein 1939 – Kausche et al – Saw virus particles (TMV) for the first time with the help of electron microscope 1956 – Gierrer and Schramm – Showed that nucleic acid is the infectious agent Also investigated about double standard RNA viruses (ds RNA) 1967 – Doi et al – First observed Phytoplasma (In mulberry dwarf disease) 1971 – Dienner and Raymer – reported 1st viroid disease potato spindle tuber viroid. 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. The Four Koch postulates (Robert koch) 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 - 4th Koch postulate was given by E. F. Smith
- 9. General characters of fungi The branch of biology that deals with fungi is called ‘Mycology’ Fungus is a Latin word which means ‘Mushroom’ 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 (or) The hyphal mass or network of hyphae constituting the body (thallus) of the fungus is called as mycelium 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 Septa – The cross walls which divide the hypha into cells are called septa
- 10. 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 Hyphal modifications Mycelium of higher fungi is organised into loosely or compactly woven tissues, called fungal tissues/ plectenchyma. They are of two types Prosenchyma – loosely woven fungal tissues in which the individual hypha lie parallel to one another Pseudoparenchyma: compactly woven fungal tissue with more or less isometric resembling parenchyma of higher plants Stromata – Compact matters like structure made up of parenchyma and pseudoparenchyma usually form fruiting bodies off fungi of various shapes and sizes Eg – Acervuli (Colletotrichum), Sporodochia (Fusarium) 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 1. Asexual reproduction – It does not involve the union of nuclei or gametes and hence called as somatic or vegetative reproduction 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
- 11. Flagellum – Hair like structure that serves a motile cell (locomotory organ) Anterior (episthocont) – Posterior (opisthocont) - Axoneme – feather like a central rachis, the hair of flagella is called flimmers hairs/ mastogoneme Conidia- a spore produced asexually by various fungi at the tip of a specialized hypha. Conidiophore – The conidiophore may be free or aggregation of aggregated to form compound conidiophore/ fruiting bodies on which conidia are produced 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 It is thick walled and contains reserve food materials to withstand unfoavorble conditions Gemmae – Chlamydospores dispersed inn water currents is called gemmae
- 12. 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 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
- 13. 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 Homothallic - Fungi in which every thallus is sexually self-fertile. The male gametes fertilize the female gametes of the same mycelium Eg - common in Ascomycota and rare in Basidiomycota Heterothallic – The fungal thallus is sexually self-sterile and requires another compatible thallus of different mating types for sexual reproduction. The male gametes fertilize the female gametes of another sexually compatible mycelium. The phenomenon of heterothallism was reported by A. F. Blakeslee (1904) in Mucor Eg – Oomycota, Zygomycota and Basidiomycota Types of sexual spores – Oospore – globose, yellow to dark brown with two layer wall and a central oil globule in the form of lipids as food material Zygospore - thick walled resting diploid sexual spore Ascospore - haploid sexual resting spore Basidiospore - exogenous sexual spore
- 14. 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
- 16. 1. Life cycle of club root of cabbage – Plasmodiophora brassicae Systemic classification :- Domain – Eukarya Kingdom – Protozoa Phylum – Plasmodiophoromycota Class - Plasmodiophoromycetes Order – Plasmodiophorales Family – Plasmodiophoraceae Genus – Plasmodiophora Species – brassicae Symptoms – roots decay, followed by yellowing, permanent wilting or retarded growth, hypertrophy and hyperplasia occurs LIFE CYCLE Infected host roots gets decayed, spores are released into soil, the spores germinated immediately with the help of root exudates. During germination a naked spherical pears shaped uninucleate zoospore with biflagellate of unequal length A phase Zoospores get attached to the surface of the roots Eventually, inactivation of flagella, retraction of axonemes and encystment of zoospores takes place By punching the host cell the zoospores entered into the host cells, these zoospores are called multinucleate primary plasmodium or ‘Myxoamoeba’ The protoplast increases in size and undergoes cruciform divisions resulting in formation of plasmodium Later these multinucleate segments are delimited, each one develop into a zoosporangium The plasmodium consists of several sporangia. The sporangia become attached to the to the host cell Each sporangium form 4-8 uninucleate biflagellate zoospores are released through a pore, lateron zoospores function as a gametes B phase Zoospore settled on the root hairs, shreds flagella and entered into the cortex of the root cells Each of binucleate plasmodium enlarges and undergoes repeated mitotic divisions to form multinucleate body referred as multinucleate secondary plasmodium Hypertrophy – abnormal enlargement of cells (increase in number of cells) Hyperplasia – increase in number of cells (increase cell divisions)
- 17. These multinucleate secondary plasmodium get hypertrophied and takes place club The karyogamy takes diploid nuclei are formed, then after meiosis Akarote stage – Diploid nuclei of the plasmodium at the time of spore formation forms a special phase, during this phase the nuclei seem to be disappear and reappears during prophase of meiosis. Several haploid resting spores are formed and they liberate and infect host. (Note - while studying keep the diagram with you, then it will be very easy to understand) 2. Life cycle of damping off of vegetables – Pythium aphanidermatum Systemic classification :- Domain – Eukarya Kingdom – Chromista Phylum – Oomycota Class – Oomycetes Order – Pythiales Family – Pythiaceae Genus – Pythium Species – aphanidermatum Symptoms Pre emergence damping off – seeds and radicles rots before the seedling emergence out of the soil Post emergence damping off – newly emerging seedlings are killed at ground level after emerge from the soil Asexual reproduction – Mycelium consists of coenocytic hyphae, hyphae is both intercellular and intracellular. No haustoria are produced Pythium produces simple branched and globose zoosporangia (produces at terminal or intercalary) Germination is either zoospores on germtube, sporangiospore consists of sporangia with bubble like vesicle, the sporangial protoplast moves rapidly through tube into vesicle and appears remains delimitation of zoospores takes place Zoospore are released in a rocking motion and bounces on the vesicle The reniform zoospores are biflagellate with anterior tinsel and posterior whiplash type, spores come in rest and encyst and germinate by producing germ tube Sexual reproduction Sexual reproduction is oogmous and takes place by gametangial contact The male sex organ is antheridium and female is oogonium Upon the gametangial contact, a fertilization tube develops and penetrates the oogonial wall and enter the periplasm In the meantime meiosis takes place only functional nuclei remains, other disintegrate.
- 18. Now male nuclei passes to female nuclei (oosphere) through fertilization tube, which forms zygote The oospore develop a thick wall around it self and germinate by using germination tube (if favourable conditions occurs it germinates, otherwise it undergoes resting period) 3. Life cycle of late blight of potato – Phytophthora infestans Domain – Eukarya Kingdom – Chromista Phylum – Oomycota Class – Oomycetes Order – Pernosporales Family – Pernosporaceae Genus – Phytophthora Species – infestans Symptoms – ‘Phytophthotra’ means plant destroyer, water soaked light brown lesions develop on the leaves and later enlarges and cover the entire leaf, petiole and stem. Rotten portion emits characteristic odour. Asexual life cycle – Sporangia are borne aerial sympodially branched sporangiophore arise directly from internal mycelium Hyphae is inter and intracellular profusely branched and produced finger like haustoria The sporangiophores are with characteristic swellings at the nodes of indeterminate growth On falling suitable host the sporangia germinate (< 15o C) favours the zoospore production, high temperature favours the germ tube formation (> 20 o C) Sexual life cycle Sexual reproduction takes place means of antheridia and oogonia of opposite mating types Oogonia penetrates and go through the antheridia and form a globose structure above the antheridia is called amphigynous antheridia Migration of antheridium nucleus into oogonial wall by fertilization tube The fertilized egg secretes a heavy wall around it self and become oospore Oospore germinates by means of germ tube and produces zoospore and produced new thalli.
- 19. 4. 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 teliospores – 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
- 20. Types of rust – Autoecious rust – Completes its entire life cycle in a single host Heteroecious rust - Requires genetically two hosts to complete their life cycle Autoecious macrocyclic rust – Eg – B – Bean rust F – Flax rust S - Sunflower rust S - Safflower rust Autoecious demicyclic rust – Eg – Rubus orange rust – Gymnoconia peckiana Heteroecious macrocyclic – Eg – Wheat stem rust – Puccinia graminis tritici White pine blister blight – Cronartium rubicola Heteroecious demicyclic – Eg – Cedar apple rust – Gymnosporangium juniperi viriginianae
- 21. Taxonomy of fungi and fungi like organisms Taxonomy is a part of biological science which deals with the study of naming and classification of organisms Grouping of fungi and fungi like organisms by taxonomists Taxonomist Groupings / classification Name of the grouping Linnaeus (1753) 2 kingdoms Vegetabilia Animalia Ernst Haeckel (1866) 3 kingdoms Protista Plantae Animalia Herbert Copeland (1956) 4 kingdoms Monera Protista Plantae Animalia Whittaker (1969) 5 kingdoms Monera Protista Fungi Plantae Animalia Carl Woese (1977) 6 kingdoms Eubacteria Archaebacteria Protista Fungi Plantae Animalia Chatton (1937) 2 empires Eukaryota, Prokaryota Carl Woese (1990) 3 domains Bacteria Archaea Eukarya 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) Each fungus has unique scientific name that indicates its taxonomic placement among other organisms. The scientific names are Latin names assignee to particular fungus based on binomial system of nomenclature of to identify organisms throughout the world. The first part is binomial name is the genus and the second is the Specific species the genus
- 22. and species have no fixed endings. The genus name maybe common to several species, but the combination applies to only one species in the entire system of classification. 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 According to the International Code of Nomenclature for algae. fungi and plants (ICN), the following ‘suffixes’ are used for phyla and other categories of a fungal taxon Phylum ends with – mycota Sub-phylum ends with – mycotina Class ends with – mycetes Subclass ends with - mycetidae Order ends with – ales Family ends with – aceae
- 23. 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
- 24. Bacteria The term bacteria was coined by – Ehrenberg Size of bacteria ranges from – 0.5 to 1.0 µm breadth and 2.0 to 5.0 µm in length 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 Anton van leeuwenhoek (1676 ) discovered the microbial world with his simple microscope . ‘’Dear god what marvels they are in so small a creature’’ Leeuwenhoek 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 Bacteria was coined by Ehrenberg Father of bacteriology – Anton van leewenhoek Father of plant bacteriology – E. F. Smith Father of Indian plant bacteriology – M. K. Patel
- 25. Structure of bacterial cell Cell wall - The cell walls of bacteria and cyanobacteria differ from plants in being made of peptidoglycan/ mucopepetide and not cellulose. Mucopeptide is a polymer of NAG (N-acetyl glucasamine) and NAM(N-acetyl muric acid) joined by b 1-4 linkage The cell wall of gram+ve and gram-ve bacteria are differ in their chemical composition. The wall of Gram+ve bacteria is homogenious containing 85% more of mucopeptides and simple polysaccharide ,like teichoic acid which are polymers of ribitol and glycerol phosphates,teichoic acid serves as antigen and also regulate ions. The cell wall of gram –ve bacteria contains only 3-12%of mucopeptides,the rest being lipoprotein and polysaccharide. Differences between gram+ve and gram-ve bacteria Gram+ve Gram-ve 1.Teichoic acid present 1. Teichoic acid absent 2.homogenois layer 2. three(3)layers 3.major portion of cell wall is mucopeptides (85%) 3. mucopetides (3-12%) 4.protoplast completely digested cellwall 4. sphaeroplast 5.L,P rings are present 5. L,P,M,S rings are present 6. while stating it produce violet/purple in colour 6. while stating it produce pink colour 7.Ex.bacillus,streptomycin, Corynebacterium 7. most of the bacterium are gram-ve 8.Much rigid due to the presence of greater amount of muciopeptides 8. Less rigid due to the plastic nature of lipoprotein, lipopolysaccaride
- 26. Pili/ fimbriae - fimbriae are hair like structure that are observed as surface appendages on some bacteria ,fimbriae are common in plant pathogenic bacteria. Pili are also hair like structure found in some bacteria which are elongate, rigid, tubular appendages made of special protein called pilin, these have so far been reported in gram negative bacterium where they serve to connect to cells during conjugation (also called sex pili )and allows the DNA to pass from donor to recipient. Flagella : these are the organs used for locomotion in motile forms and many times longer than bacteria (4-5 times) than the bacterial cell, they are fundamentally different from the flagella or cilia of eukaryotes in lacking the ‘9+2’ arrangements. Flagella or cilia of eukaryotic cells are , morphologically and physiologically similar. 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 The plasmids: bacterial plasmid is circular, extra chromosomal double standard DNA , which provides additional genetic information which, tought not essential for basic life process, help the bacteria in various ways. Although plasmids usually contains 1-5% of the DNA, The affect of the small genetic information can decide survival, as happens with the antibiotic resistance gene. Capsule/ slime layer – which protects the bacteria from desiccation (refere slide share for more diagrammatic representation and inflation – Hima Shankar)
- 27. Growth and reproduction in bacteria: Bacteria multiply by all the known methods of reproduction. The novel methods of sexual reproduction that occurs in bacteria, though different from classical types involving karyogamy and meiosis, bring about the same end result Viz., genetic recombination. The bacteria reproduce asexually by fission, endospores, cysts, fragmentation, sporangiospores, and conidia. The asexual reproduction is represented by conjugation, transformation, transduction, transduction and lysogenic conversion. I. Asexual reproduction: Fission: The bacterial cell divided into two by fission. Mostly it is a binary fission in which the two daughter cells are identical. Division is a very quick process and it is completed in 30 minutes. II. Sexual reproduction: Until 1940 ,ant idea of sexual reproduction in bacteria was considered ridiculous. Bacterial cytology was a diffuse and a controversial subject.even the genetic material was not clearey demonstrated. 1 .Conjugation: The transfer of genetic material from one bacterial cell to another bacterial cell during conjugation. The two cells are genetically different, the donor cell transferred part of its genome to the recipient cell. This was discovered by Lederberg and Tatum in 1946 on Escherichia coli. 2. Transformation: In 1928 Frederik Griffith, an english bacteriologist, made an important observation which initiated a biological revolution. When he was working with the bacterium Pneumococcus pneumonia (then called diplococcus) the causal organism of pneumonia, he observed DNA from one type of bacterium is incorporated into the genetic makeup of another organism during transformation, A new individual which derives some of its genes from two genetically different parents is formed during this process. 3. Transduction: Lederberg and his student Zinder in 1951 started looking for recombination in salmonella tymphimurium , They used the same techniques which Lederberg and Tatum had used with E.coli. They obtained the nutritionally deficient
- 28. mutants (auxotrophs) which failed to grow on the mineral medium. When a mixture of the two mutants are plated together ,recombination appers in a few cases but not with other stains, When they analysed the cause they discoverd a new type of gene exchange, , Which involved the medium bacteriophage. Zinder and Lederberg described the new method of of gene transfer in 1952 as Transduction. Genetic mechanism Organism Scientist discovered Year Conjugation E. coli Lederberg and Tatum 1946 Transformation Pneumonia Griffith 1928 Transduction Salmonella Lederberg and Zinder berg 1952 (For easy remembering to students CTT = EPS Where C – conjugation, T- Transformation, T – Transduction that happens in organisms of - E – E. Coli, P – Pneumonia, S – Salmonella, in an order makes the right sense of answers) (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) The 1st plant pathogenic bacteria the genome which was completely sequenced was - Xylella fastidiosa (in 2000 by a Brazilian consortium/association, scientist associated with genome sequencing is A. J. G. Simpson) Pierce disease of grapes is transmitted by – Glassy winged sharp shooter (Homolodisca coagulata later name changed to Homolodisca vitripennis) Mode of entry of plant pathogenic bacteria Specialized structure (enters through) Causal organism Causal organism Hydathodes Black rot of cabbage/ Crucifers Xanthomonas campestris pv. campestris Floral parts (Nectaris) Fire blight of apple and pear Erwinia amylovora Lenticels Potato common scab Streptomyces scabies Trichomes Bacterial canker of tomato Clavibacter michiganensis Stomata Bacterial leaf streak Xanthomonas oryzae pv. oryzicola Citrus canker Xanthomonas citri Bacterial classification is mainly based on :- Bergey’s manual of determinative bacteriology (1923) Bergey’s manual of systemic bacteriology, 1st edition (1984) Bergey’s manual of systemic bacteriology 2nd edition (2004)
- 29. Virology Study of plant virus is called Plant Virology The term virus was derived from ‘Latin’ word which means Poison/ venom/ slimy liquid Virus – virus is a sub-microscopic, infectious, obligate intracellular parasite which do not replicate without host Capsid – protein coat or shell which encloses the viral genome Vector – An agent/ organism which carries virus Bacteriophage - virus which infects the bacteria (which means bacteria eater) 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. 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 Protein coat only protects nucleic acid (NA), which having no role in disease transmission and spread. GENOME: The genome may be RNA or DNA, either of which may be single stranded (ss) or double stranded (ds). CAPSID SYMMETRY: Found in either of two geometric configuration helical (rod shaped or coiled) or icosahedral (spherical or symmetrical). 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. Almost all plant pathogenic viruses contains – 5-40 % NA, 60-95 % protein coat TMV contains 5 % NA, 95 % protein coat All plant pathogenic viruses are inactivated/ killed at 50 - 60 0 C, whereas TMV requires 93 0 C Cell to cell movement of virus is mediated by Plasmodesmata
- 30. Short note on TMV Positive (+) ss RNA viruses which infects wide range of plants, especially tobacco TMV belongs to the genus Tobamovirus 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 Multiplication of plant viruses Virus initially enters into the host through wounds or physical injuries made by vectors Uncoating of protein coat Production of mRNA Translation of mRNA Replication of viral genome Assembly of progeny of virus Note – RNA viruses multiply in ‘Cytoplasm’ DNA viruses multiply in ‘Nucleus’ COMMON SYMPTOMS OF VIRUS 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. 1. Stunting and dwarfing. Reduced plant size is a common symptom of most virus infections and is most likely to be found in association with other symptoms. Growth may be reduced evenly throughout the plant or the stunting may be confined to certain parts or organs of the plant. Along with the aerial parts of the infected plant, root growth may also be stunted (e-g) Pea stunt disease caused by Red clover vein mosaic virus; Rice dwarf disease; Peanut stunt disease; Barley yellow dwarf disease. 2. Mosaic. Mosaic is one of the most important symptoms caused by virus infection in many plant species. The infected areas are usually pale green or chlorotic due to loss or reduced production of chlorophyll. (e-g) Tobacco mosaic; Tomato mosaic; Cucumber mosaic; 3. Yellow mosaic. The leaves of infected plants develop more of irregular yellow patches than the green portion and the infected plants are stunted (e-g) Bean yellow mosaic; Barley yellow mosaic. 4. Chlorosis. In the infected plants, the whole leaf may become chlorotic due to decreased chlorophyll production and break down of chloroplasts.
- 31. (e-g) Wheat yellow leaf; Potato yellow dwarf; Barley yellow dwarf; Cowpea chlorotic mottle; Beet yellows. 5. Vein clearing. Here the cells adjacent to the vein becomes translucent, while the interveinal areas remain green (e-g) Okra vein clearing; Lettuce vein clearing. 6. Vein banding. In the infected plant, the area adjacent to the veins of the leaf remain green, in contrast to the remaining areas of the leaf, which may be chlorotic (e-g) Chilli vein banding caused by Tobacco etch virus. 7. Ring-spotting. The disease is restricted to a ring or broken ring of infected cells. The infected cells may be chlorotic or necrotic and sometimes the rings may occur in concentric circles. (e-g) Cabbage necrotic ringspot; Chlorotic ringspot and Broken ringspot of celery; Tobacco chlorotic ringspot; 8. Necrosis. In some cases, the veins may become necrotic and the necrosis may spread to the stem and root apices and ultimately the plant may be killed. Necrosis may occur on fruits or seeds also. (e-g) Tobacco necrosis; Cucumber necrosis; Cacao necrosis; Clover necrotic mosaic. 9. Enations or tumors. Due to infection by some viruses, characteristic tumor-like outgrowths are formed on the leaves and roots. (e-g) Pea enation mosaic; Sugarcane Fiji disease; Maize rough dwarf - wart-like outgrowths are produced on the lower surface of leaves due to abnormal proliferation of the underlying phloem tissues; tumors on clover roots caused by Wound tumor virus. 10. Leaf distortion. In some virus infections, the leaf lamina is affected and it may become irregularly distorted or become strap-like. (e-g) Bean common mosaic in Phaseolus vulgaris; Strawberry latent ringspot in celery; Tobacco mosaic virus in tomatoes; Bean leaf roll virus in Vicia faba; Beet leaf curl; Tobacco leaf curl 11. Leaf roll. The leaf lamina roll and curl upwards (e-g) Potato leaf roll, Bean leaf roll and Pea leaf roll. Virus classified based in ICNV and ICTV ICNV – international committee on nomenclature of virus (1966) ICTV – international committee on taxonomy of virus (1973)
- 32. Viroids Viroids – Small circular, single standard RNA without protein coat(nucleic acid devoid of protein coat), consists of 250-370 nucleotides Viroid was discovered by Diener (1971) 1st 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) 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 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 1st phytoplasmal disease – Mulberry dwarf Eg – Little leaf of brinjal Sesame phyllody Coconut lethal yellowing Rice yellow dwarf Apple proliferation
- 33. 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 1st spiroplasmal disease – Corn stunt Eg – citrus stub born Pear decline 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 ALGAE Study of algae is called – Phycology/ Algology Father of Modern Phycology/ Algology - William Henry Harvey Father of Indian Algology – M. O. P. Iyengar Red rust of guava is caused by – Cephaleuros parasiticus
- 34. Some important plant diseases 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