Biocontrol potential of endophytic Bacillus velezensis strain QSE-21 against postharvest grey mould of fruit

Abstract Postharvest grey mould caused by Botrytis cinerea severely affects the storage and quality of fruit. Plant endophytic bacteria are potential new sources of biocontrol agents for safe and “green” control of fruit diseases. In this study, a bacterial strain, QSE-21, was isolated from tomato stems and identified as Bacillus velezensis. QSE-21 strain and its cell-free supernatant (CFS) strongly inhibited mycelial growth, conidia production and conidia germination of B. cinerea. The CFS effectively protected against B. cinerea infection on different tested fruit, controlling infection by 67.3 % and 60.5 % in tomatoes and apples, respectively. Transcriptome analysis of B. cinerea under QSE-21 strain stress revealed that a large number of genes widely involved in diverse biological processes, such as DNA replication, mismatch repair and carbohydrate metabolism, were differentially expressed. Moreover, CFS rapidly upregulated the expression of genes involved in the jasmonic acid (JA) signalling pathway in tomato fruit. Collectively, our results indicate that QSE-21 strain has the potential to be used as a biocontrol agent for B. cinerea in postharvest fruit and present a global view of B. cinerea gene expression in response to QSE-21 strain, providing a theoretical reference for elucidation of the molecular mechanisms underlying CFS-mediated biocontrol.