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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

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 Phytopathology 66: 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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