Plant pathology

1. Plant pathology by Prof. Dr. Amany Abo Ellil

2. Part IIIFungal diseases • Introduction • Characteristics of plant pathogenic fungi • Classification of plant pathogenic fungi • Diseases caused by Fungal Like Organisms • Diseased caused by Myxomycota • Diseased caused by Plasmodiophoromycetes • Diseased caused by Oomycets • Diseases caused by True Fungi • Diseased caused by Chytridiomycota • Diseased caused by Zygomycota • Diseased caused by Ascomycota • Diseased caused by Basidiomycota • Diseased caused by Deuteromycota

3. Introduction • Fungi are small, generally microscopic, eukaryotic, usually filamentous, branched, spore – bearing organisms that lack chlorophyll. • Fungi have cell walls that contain chitin and glucans (but no cellulose) as the skeletal components. • These are embedded in a matrix of polysaccharides and glycoproteins.

4. Ecology • Almost all plant pathogenic fungi spend part of their lives on their host plants and part in the soil or in plant debris on the soil. • Biotrophs • Hemibiotrophs • Facultative saprophytes • Facultative parasites

5. During the parasitic phase, fungi assume various positions in relation to the plant cells and tissues.

6. Reproductive bodies [spore] are produced at or very near to surface ensure their prompt and efficient dissemination.

7. Overseason

8. Dissemination • Active • Passive

9. Classification of plant pathogenic fungi • Fungal-like organisms • Kingdom: Protozoa • Phylum: Myxomycota • Phylum: Plasmodiophoromycota • Kingdom: Cromista • Phylum: Oomycetes

10. Kingdom: True Fungi • Phylum: Chytridiomycota • Phylum: Zygomycota • Phylum: Ascomycota • Phylum: Basidiomycota • Phylum:Deuteromycota

11. Disease caused by fungal like organism • Disease caused by myxomycota • [myxomycetes] • Slime Mould • Physarum • Fuligo • Mucilago • Didymium

14. Diseases caused by Plasmodiophoromycota • Club root of crucifers caused by • Plasmodiophora brassicae • Root disease of cereals and grasses caused by • Polymyxa spp • Powdery scab of potato caused by • Spongospora subterranea

18. Polymyxa graminis is vector of several viruses of grain crops,peanuts • P.betae is vector of beet necrotic yellow vein virus. • Spongospora is vector of potato moptop virus.

23. Diseases caused by Cromista • Oomycota • Saprolegniales • Aphanomyces caused root rot; pea sugar beet • Peronosporales. • Pythium caused seed rot; root rot; seedling damping off. • Phytophthora caused late blight of potato ;root rot; fruit rot; stem rot; canker and diebacks of tree.

24. Prenospora; Bremia; PlasmoparaPseudopronospora caused downy mildew of cucurbits, lettuce, vitis, tobacco (dicot) . • Peronosclerospora; sclerophthora ;Sclerospora caused downy mildew of corn; sorghum; sugar cane(mocot). • Albugo caused white rust of crucifers.

25. Late blight of potato • Symptoms • In moist weather • In dry weather • Pathogen: Phytophthora infestans • Mating type A1 and A2

30. Development of disease • Epidemic disease • Overwinter • Two Mating types • Gene coding for enzyme(B-1,3 glucanase) defense related gene • Complex interest

33. Control • Combination of sanitary measures, resistant varieties and well time chemical spray may be obtain a satisfactory level of control of disease. • Systemic Acquired Resistance(SAR) by inducing DL3 amino-butyric acid or preinoculation with tobacco necrosis virus.

34. Downy mildew • Cromista Oomycetes prenosporaceae Obligate parasite Catastrophic and Spectacular epidemic on cool or warm not hot weather. It needs a film of water and high relative humidity. Disease stops on hot and dry weather.

36. Pathogen causes systemic shoot infection in young plant. • Pathogen causes local infection in old plant and locally systemic Infection in young tissue. • It destroys 40-90% of young plant • Severity losses of crop depend on cool & wet weather • Ucontrollable

37. Downy mildewMost common genera • Bremia • Haloperonospora • Peronospora • Peronosclerospora • Plasmopara • Pseudoperonospora • Sclerophthora • Sclerospora

38. Downy mildew of grape • Plasmopara viticola • Most suscept is Vitis vinifera • Severe losses through • 1-killing of leaf and defoliation • 2-low quality and entirely destroy grapes • 3-weakening,dwarfing and killing of young shoot.

39. Symptoms & signs

40. Small pale yellow Irregular Infected area killed White downy growth spots on upper surface turn brown underside of spot

41. Leatheary wrinkled reddish marbling to brown coloration

42. Plasmopara viticola • In one season ,it can easily destroy 50-70% of crop.

43. Development of disease • Overwinter: oospore in dead plant and mycelium in infected but not killed twigs • First inoculum : sporangium or zoospore • Infection: through stoma and lenticels • Habitat: intercellular with haustoria • Dissemination: by wind or water • Habit : biotrophs • Interest : complicated( 2ry infection cycle) • Cycle spend 5-18 days depending on temp, humidity and varietal susceptibility • Hot and dry stop disease development • 0

45. Control • American grape varieties are resistant European grape vinifera is quite susceptible. • Protection by copper based fungicides,bordeaux mixture (broad spectrum protective fungicide). • Application 7-10 days interval before blooming • Disease prediction depends on duration of leaf wetness, relative humidity and temperature.

46. Disease caused by True fungi Chytridiomcetes-Zygomycetes- Ascomycetes- Deuteromycetes- Basidiomycetes.

47. Disease caused by Ascomycota

48. Powdery Mildew Most common, wide spread affect all kinds of plant except gymnosperm

49. Obligate parasites