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Rusts! Smuts & Bunts! Wood & Root Rots! Rots & Damping-Off!

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Presentation on theme: "Rusts! Smuts & Bunts! Wood & Root Rots! Rots & Damping-Off!"— Presentation transcript:

1 Rusts! Smuts & Bunts! Wood & Root Rots! Rots & Damping-Off!

2 Somatic ploidy 2nnn+n Chitin wall Motile zoospores yesno Septate hyphae noyes Sexual spore no Oomycota Ascomycota Basidiomycota yes Oospore Asco- spore Basidio- spore

3  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  Sexual reproduction structure: Basidium - “club”  Basidiospores (1n) 4 per basidium n

5 Hymenomycetes Mushrooms Urediniomycetes Rusts Ustilaginomycetes Smuts Tom Volk

6  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 Urediospores erupting from uredinia on wheat stem. a.k.a. Stem Rust, Black Rust USDA, ARS

8  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  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 Basidiospores Spermatia and receptive hyphae Urediospore Teliospore Aeciospore BarberryWheat 1 5 4 3 2

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

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

13 Aeciospores (n+n) on underside of barberry leaf. Infect only wheat plants Spermacia (n-) and (n+) Receptive Hyphae on upper barberry leaf surface

14 Puccinia graminis 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. Urediospores ( n+n) erupt from upper leaf surface. Repeating stage. Aeciospores (n+n) Stomate

16 Puccinia graminis uredia erupting from upper epidermis of wheat leaf. Urediospores

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

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

19 Basidiospores Spermatia and receptive hyphae Urediospore Teliospore Aeciospore BarberryWheat A MACROCYCLIC RUST

20  Resistant varieties  Fungicides Many applications required = $$$ Scouting and Forecasting  Barberry Eradication


22 E.C.Stakeman and J.G.Harrar. 1957

23  Formae speciales (f.sp.) – “special forms” Puccinia graminis f.sp. tritici - wheat Puccinia graminis f.sp. secalis – barley  Pathogen recognizes host morphology – only then will it penetrate and infect. Guard cells of stomata Leaf topography

24 Wynn, W. 1976. Phytopathology 66: 136-146 Urediospores Bean rust fungus - Uromyces phaseoli

25 guard cells stomate urediospore appressorium


27 Allen et al., Phytopathology, 1991 Uromyces Puccinia Polystyrene membranes with 6.7um ridges thigmotropism

28  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.

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

30  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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