Endophytic Bacillus amyloliquefaciens Mdgb15 is a potential biocontrol agent against tree peony gray mold caused by Botrytis cinerea

Abstract

Abstract Botrytis cinerea is the causal agent of gray mold disease affecting Paeoniaceae plants. The present study focuses on the potential of Bacillus amyloliquefaciens Mdgb15 as a promising biological control agent toward B.cinerea. The strain Mdgb15 showed the highest inhibition rate (55.56%) against B. cinerea growth and was effective in controlling tree peony gray mold in detached leaves. A conventional PCR with three specific primer pairs detected lipopetides substance synthesis genes of Mdgb15. The results revealed that Mdgb15 had srfAA, fenA and ituD genes, which resulted in the production of surfactin, fengycin and iturin. An accurate RT-PCR protocol with designed specific primers was further developed to expression characterize of lipopetides synthesis gene of Mdgb15.The RT-qPCR analysis revealed that the expression of ituD and fenA genes in Mdgb15 was remarkably up-regulated during the coculture with B. cinerea. Following the lipopeptides was extracted by acid precipitation of culture filtrate of Mdgb15 and was separated by using Sephadex Gel chromatography column. Three separated fractions exhibited strong antifungal activity against B. cinerea, and were identified as bacillomycin D by MALDI-TOF-MS analysis. This study has demonstrated that B. amyloliquefaciens Mdgb15 is considered as a future potential new biocontrol agent for controlling tree peony gray mold disease. It suggests that the antifungal mechanisms of Mdgb15 may be at least partially associated with its ability to secret bacillomycin D.