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Basidiomycete Plant Pathogens

Basidiomycete Plant Pathogens. Wood & Root Rots!. Rusts!. Smuts & Bunts!. Rots & Damping-Off!. Review: Pathogen Characteristics. Oospore. Asco -spore. Basidio -spore. no. Oomycota. yes. Ascomycota. yes. Basidiomycota. Basidiomycota. Mushrooms Agaricus Lentinula (shitake)

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Basidiomycete Plant Pathogens

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  1. Basidiomycete Plant Pathogens Wood & Root Rots! Rusts! Smuts & Bunts! Rots & Damping-Off!

  2. Review: Pathogen Characteristics Oospore • Asco-spore • Basidio-spore no Oomycota yes Ascomycota yes Basidiomycota

  3. Basidiomycota • Mushrooms • Agaricus • Lentinula(shitake) • Aminita (destroying angel) • Mycorrhizal fungi – forest ecosystems • Wood decay fungi • Pathogens on major crops: • Rusts of grains, soybean, coffee, ornamentals • Smuts of small grains and corn

  4. Basidio Sexual Reproduction • Sexual reproduction structure: • Basidium - “club” • Basidiospores (1n) • 4 per basidium n www.apsnet.org

  5. Tom Volk Basidiomycota apsnet.org

  6. Uredinales - Rusts • Puccinia – grass and cereal rusts • Phakopsora – Soybean Rust • Gymnosporangium – Cedar-Apple Rust • Hemileia – Coffee Rust • Cronartium – White Pine Blister Rust • Uromyces – carnation and bean rusts • Phregmidium – Orange rust of blackberry

  7. Wheat RustPucciniagraminis Urediospores erupting from uredinia on wheat stem. a.k.a. Stem Rust, Black Rust USDA, ARS

  8. Rusts in History • Described in Bible and Broadway: • Famine in Joseph and Amazing Technicolor Dreamcoat story • In writings of Theophrastus • (“Father of Botany”) • Robigus – Roman rust god • Honored by Robigalia – sacrificed reddish-colored animals

  9. Pucciniagraminis • Obligate biotroph– no saprophytic stage. • Heteroecious– 2 hosts required for lifecycle: • Grass species (monocot) • Barberry (dicot) • Polycyclic pathogen • Aerial urediospores spread 100s of miles.

  10. Spermatia and receptive hyphae Basidiospores Urediospore Lifecycle of Pucciniagraminis 2 1 3 Aeciospore Barberry Wheat 5 Teliospore 4

  11. Barberry infected by Basidiospore (n) in spring (primary inoculum) Barberry Wheat Overwinters as Teliospore (n+n) in crop debris

  12. Dikaryotic hyphae (n+n) form on Barberry. Direct penetration of barberry leaf

  13. Spermacia (n-) and (n+) Receptive Hyphae on upper barberry leaf surface Aeciospores (n+n) on underside of barberry leaf. Infect only wheat plants Pucciniagraminis Spermagonia (upper) and aecia (lower) on leaf of barberry seen in cross section by light microscopyAecia form from (n+n) hyphae created by fusion of receptive hyphae with spermatia of opposite mating type

  14. Pucciniagraminis infection of barberry showing aecia on lower leaf surface

  15. Aeciospores (n+n) wind blown to wheat host plants and infect leaves by penetrating stomates. Aeciospores (n+n) Urediospores ( n+n) erupt from upper leaf surface. Repeating stage. Stomate

  16. Pucciniagraminisuredia erupting from upper epidermis of wheat leaf. Urediospores

  17. Wheat hosts senesce and dry at end of season Teliospores n+n Urediospores n+n Barberry Wheat In Teliospore n+n  2n  4 (1n) Meiosis occurs

  18. PucciniagraminisTeliospore produced at end of season when grain plants begin to senesce and dry down Dark Teliospores Uredia shift production to thick-walled dark colored 2-celled Teliospores(n+n) that overwinter in debris Rusty Urediospores

  19. Spermatia and receptive hyphae Basidiospores Urediospore Life cycle of Pucciniagraminis Aeciospore Barberry Wheat Teliospore A MACROCYCLIC RUST

  20. Control of Wheat Rust • Resistant varieties • Fungicides • Many applications required = $$$ • Scouting and Forecasting • Barberry Eradication

  21. Spread of P. graminisin 1923 E.C.Stakeman and J.G.Harrar. 1957

  22. Rusts are very specific • Formaespeciales (f.sp.) – “special forms” • Pucciniagraminisf.sp. tritici - wheat • Pucciniagraminisf.sp. secalis– barley • Pathogen recognizes host morphology – only then will it penetrate and infect. • Guard cells of stomata • Leaf topography

  23. Stomate architecture influences penetration. Wynn, W. 1976. Phytopathology 66: 136-146Urediospores Bean rust fungus - Uromycesphaseoli

  24. Host Specificity appressorium guard cells stomate urediospore Bean rust fungus (Uromycesphaseoli) penetrating stomate in bean leaf host.

  25. Rust does not recognize non-host stomata: No penetration, no infection

  26. Host topography affects appressorium formation Polystyrene membranes with 6.7um ridges Uromyces Puccinia thigmotropism Allen et al., Phytopathology, 1991

  27. P. graminisas biological weapon • Rapidly spreading (aerial), polycyclic pathogen capable of destroying an economically important crop. • Potential use in bio-terrorism/warfare: • Rust pandemic would have negative economic, food security and psychological effects. • Has been weaponized in the past by USSR and US Army Biological Weapons lab at Fort Detrick, MD. • 1970 – USSR & USA signed Biological Weapons Treaty banning development and testing of biological warfare weapons.

  28. USDA-ARS Foreign Disease Containment Greenhouse Fort Detrick, Frederick, MD

  29. “New” race of P. graminis: UG99 • Uganda, 1999 • Defeats more of the known resistance genes than any other known strain. • Could infect 90% of world’s wheat varieties. • $26.8 million grant from the Bill & Melinda Gates Foundation.

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