Ascomycete communities associated with suppression of Sclerotium rolfsii in compost

Composts are known to facilitate biological control of soilborne plant pathogens and offer an opportunity to introduce and establish biocontrol agents in soils. In this study, biosolid composts were used for suppression of the plant-pathogenic fungus Sclerotium rolfsii. Our aim was to study the composition and development of fungal communities on and around the sclerotial surface, and to identify antagonists parasitizing S. rolfsii. By molecular profiling, we found the sclerotial environment to be enriched by some of the ascomycetes in compost, implying that sclerotia may serve as bait for compost mycoparasitic populations. Known mycoparasites such as Chaetomium, Geomyces, Penicillium, and Trichoderma species were identified and isolated, along with Thielavia and Petriella species. However, we were not able to identify any single species that could account for all of the naturally attacked sclerotia; rather, a variety of antagonists were revealed. We hypothesize that a consortium of antagonistic microorganisms parasitizes the sclerotia.