Evaluation of Bacillus amyloliquefaciens isolate BX13 for the biocontrol of Fusarium incarnatum, a causal agent of fruit rot in postharvest muskmelon

Fruit rot, caused by Fusarium spp., is one of the most severe postharvest diseases of muskmelon (Cucumis melo L.). Biological control is among the most promising and effective methods for controlling fruit and vegetable postharvest diseases, which is also healthy and safe for people and the environment. The effectiveness of a broad-spectrum antifungal Bacillus amyloliquefaciens isolate BX13 as a biocontrol agent against F. incarnatum causing muskmelon fruit rot was screened, identified, and investigated. BX13 successfully inhibited F. incarnatum growth and hence mitigated the severity of muskmelon fruit rot. A concentration of only 10 mg L-1 purified lipopeptide achieved superior inhibition to that of the fungicide azoxystrobin. Fusarium incarnatum was also well inhibited by the use of 10 mg L-1 lipopeptide during conidial germination, production, and mycelial growth with 81.4%, 78.1%, and 51.8% inhibition efficacy, respectively. In addition, the mycelia of F. incarnatum treated with lipopeptide showed folding, deformation, protoplasm aggregation, inflated hypha, swelling, and dehydration malformation. Muskmelon fruit treated with BX13 exhibited elevated activities of the resistance-related enzymes polyphenol oxidase, phenylalanine ammonia-lyase, peroxidase, and catalase. Matrix-assisted laser desorption/ionization-time of flight analysis indicated that iturin A, bacillomycin D, and mycosubtilin were the primary antifungal compounds of BX13. The purified lipopeptides from BX13, when applied at 10 mg L-1, reduced fruit rot on muskmelon by 78.2%. BX13 has significant preservation benefits on muskmelon by decreasing decay and elevating the activities of resistance-related enzymes, which has considerable promise for controlling muskmelon postharvest fruit rot.