Biocontrol ability and action mechanism of Bacillus amyloliquefaciens Baf1 against Fusarium incarnatum causing fruit rot in postharvest muskmelon (cv. Yugu) fruit

Muskmelon (Cucumis melo L. cv. Yugu) is favoured by consumers for its high quality, attractive appearance, and good palatability. However, fruit rot is a prominent threat during postharvest storage, resulting in potentially substantial serious losses. In this study, we investigated the biocontrol efficacy of Bacillus amyloliquefaciens Baf1 against fruit rot caused by Fusarium incarnatum in post-harvest Yugu muskmelon, and examined the underlying antagonistic mechanisms. Baf1 had more than 75% control effect on F. incarnatum in vitro and in vivo. In addition, Baf1 treatment effectively improved the fruit defense enzyme activities (PAL, POD, and PPO) and maintained the quality (weight loss, respiration rate, ascorbic acid and total soluble solid) of muskmelon during storage. A 5 mL/L lipopeptide extracted from Baf1 inhibited the hypha growth and conidia germination and production of F. incarnatum by 55%, 63.2%, and 65%, respectively, and caused hyphal malformation. The active antifungal substances of Baf1 were preliminarily identified as C13–C15 surfactins and C17 bacillomycin L based on matrix-assisted laser desorption ionization time-of-flight mass spectrometry. Thus, the biocontrol agent Baf1 showed great potential for inhibiting postharvest grey mould in muskmelons and could be a useful approach for enhancing the quality and storability of muskmelons.