Suppression of Ascocarp Formation inPyrenophora tritici-repentisbyLimonomyces roseipellis,a Basidiomycete from Reduced-Tillage Wheat Straw

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Abstract
A fast-growing basidiomycete, previously isolated from microbial communities of reduced-tillage wheat straw in which Pyrenophora tritici-repentis appeared to be declining, was tested in the laboratory for its ability to suppress sexual reproduction of Pyrenophora. Nonsterile straw pieces, which had been colonized by p. tritici-repentis during parasitic growth, were inoculated with the basidiomycete and incubated under various conditions of temperature and moisture. The basidiomycete reduced ascocarp and ascospore production significantly. The degree of suppression varied from 50-99%, depending on test conditions, but was especially effective in straw sheath tissue (vs. culm tissue) that was wetted daily and incubated under warm, low-humidity conditions. The basidiomycete was identified as Limonomyces roseipellis, which causes pink patch, a mild disease of turfgrass. The mechanism of antagonism is unknown but may involve mycoparasitism, as this fungus has chitinolytic ability. Although competition for nutrients also may be involved, this dose not appear to be the sole mechanism, because Trichoderma koningii, an aggressive colonist, did not significantly suppress sexual reproduction of P. tritici-repentis under any conditions tested.