Dynamics of compost microbiota during the cultivation of Agaricus bisporus in the presence of Bacillus velezensis QST713 as biocontrol agent against Trichoderma aggressivum

The edible button mushroom Agaricus bisporus is cultivated worldwide and appreciated for its organoleptic and nutritive qualities. It is nowadays cultivated at industrial scale in climatic units under controlled environmental conditions. Various organisms can trigger microbiological-induced losses, including Trichoderma aggressivum f. europaeum, the fungal agent of green-mould disease, which hinders the growth of A. bisporus mycelium. In France, the biocontrol agent Bacillus velezensis QST713 is used to control T. aggressivum and prevent production losses. Here, we evaluated the impact of B. velezensis QST713 on the natural microbiota of cultivation compost, artificially contaminated or not with the green-mould agent, under controlled conditions. Microbial enumeration and Miseq sequencing of 16S rRNA and ITS amplicons revealed the compost natural microbiota to be dominated by bacteria from the Nocardiopsaceae and Sphingobacteriaceae families, and fungi from the Chaetomiaceae family. Artificial contamination by Trichoderma aggressivum f. europaeum profoundly altered the fungal community, in contrast to B. velezensis QST713, which principally affected the abundance of the pathogen. This study provides new information on the dynamics, composition and structure of microbial communities of A. bisporus culture compost, the interactions that may occur in this ecosystem and will provide a better understanding of these biocontrol solutions for a better use of these tools.