The good fight. Minimedusa polyspora and Chaetomium globosum effectively antagonize phytopathogenic fungi in in vitro conditions

In this study, Minimedusa polyspora and Chaetomium globosum and their metabolites were assessed in vitro for their ability to inhibit growth of Alternaria alternata, Berkeleyomyces basicola, and Botrytis cinerea, gaining insights into their biocontrol mechanisms. A dual culture, an assay for volatile antimicrobial compounds effectiveness (performed in two different conditions), and a culture filtrate antifungal assay were designed to discriminate the involved mechanisms. Moreover, the culture filtrates of these strains were assessed for fungistatic and fungicidal activities (determining also the minimum inhibitory concentration and the minimum fungicidal concentration) and for the occurrence of siderophores. The results show that both M. polyspora and C. globosum inhibited, to different extents, growth of all the pathogens in the plate assays. Both culture filtrates showed fungistatic and fungicidal activities, pointing to the release of diffusible compounds as an involved biocontrol mechanism. Based on the results of this study, M. polyspora and C. globosum are promising bioprotection agents of these phytopathogens and species of interest for further studies aimed at validating their potential in in vivo conditions.