Volume 19 Part 1 Article 24: Mycoparasites isolated from Agaricus macrosporus in nature

Volume 19 Part 1 Article 24
Year 2016
Title: Mycoparasites isolated from Agaricus macrosporus in nature
Author: Kiran Lakkireddy, Weeradej Khonsuntia and Ursula Kües

White button mushroom industry is threatened by mycoparasites such as Lecanicillium fungicola causing dry bubble disease and Cladobotyrum dendroides causing cobweb disease. The pathogens infect stages in mushroom development. They induce various symptoms on the host, such as bubbles, split stipes and spotty caps and destroy their host´s hyphae. Observations on these mycopathogens in nature are however rare, possibly because they are rather overlooked. Here, we describe mycopathogens found on Agaricus macrosporus in nature. Strains were isolated and we tested their behavior with different basidiomycetes in the laboratory.

Drumstick-like closed young fruiting bodies of A. macrosporus appear regularly each year in August to November underneath a Douglas fir on the North Campus of the University of Göttingen at sunny days of pleasant temperature. The young mushrooms open within 3 days by perforating the veil at the edges of the cap. In the next 2 days, the caps flatten in order to stretch out their pinkish-brownish gills for spore release and to then degenerate. Deformed fruiting bodies of irregular stipe and cap shapes appeared in September 2015. Fluffy mycelium covered the surface of the mis-shaped parts of the fruiting bodies. Microscopic analysis revealed ascomycetous types of conidiophores producing multiple 1-3 celled conidia. Similar structures were observed on decaying stipes of overturned mushrooms. The mycopathogens were isolated from infested mushroom tissues and used to infect in the lab commercially produced Agaricus bisporus and Pleurotus ostreatus mushrooms and mycelial cultures of basidiomycetes. The pathogens were very aggressive towards A. bisporus and produced huge amounts of conidiospores on the mushrooms. P. ostreatus in contrast was highly resistant. Slight infections were observed only with one of the isolates at stipe regions of only a few P. ostreatus mushrooms. Mycelium of lab strains of Coprinopsis cinerea was attacked by the mycoparasites but not mycelium of P. ostreatus. Conidiophores, conidiospores and ITS sequencing are used to determine the identity of the isolates.

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