PBIO 117 Lecture Notes - Stem Rust, Heteroecious, Basidiomycota
27 Dec 2013
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Uredomycetes: obligate parasites, 5000 species, produce multiple spore types. Autoecious entire life cycle on one host. Heteroecious- require 2 different hosts to complete lifecycle. Spore sequence: figure 11-130: uredospore- only spore type that can infect the same host it is grown on, critical to epidemics. Cedar apple rust skips uredospore part of cycle. Stem rust on wheat (puccinia graminis: worldwide problem, very destructive, obligate parasite, macrocyclic, heteroecious (wheat & barberry, pustules weaken plant, cause water loss, disease cycle: figure 11-134. Production of uredospores are where most of the damage occurs: management. Needs living plant to survive so killing the plant is sufficient. Sexual recombination is prevented, leaves uredospores (asexual) to maintain fungicides: now fewer races of stem rust (can"t evolve) Delays epidemics are delayed by several weeks. Fungicide (too expensive: emerging threat w/ genetic resistance. New rusts have emerged that overcome sr31 resistance gene (ug99 strain)
