Antimicrobial peptide CB-M exhibits direct antifungal activity against Botrytis cinerea and induces disease resistance to gray mold in cherry tomato fruit

Gray mold is a common postharvest disease caused by Botrytis cinerea that causes fruit decay and reduces fruit storage quality. In this study, the antifungal activity of antimicrobial peptide CB-M against B. cinerea and its mechanism of action, as well as the ability of CB-M to induce disease resistance in cherry tomato fruit, were investigated. CB-M had a strong inhibitory effect on spore survival and mycelial growth of B. cinerea, and these effects were enhanced with increased CB-M concentration. Moreover, significant leakages of cellular constituents and fluorescence microscopy assay confirmed that CB-M treatment could destroy the cell membrane integrity of B. cinerea. Scanning electron microscopy observations further demonstrated obvious distortion and shriveling of B. cinerea hyphae. Gel retardation and SDS-PAGE assay showed that CB-M could likely bind to cellular DNA and degrade/inhibit protein synthesis in B. cinerea. Furthermore, preincubation with CB-M before pathogen inocu-lation significantly decreased lesion diameter and incidence of gray mold caused by B. cinerea in tomato, cherry tomato, and grape fruit throughout whole storage time. Cherry tomato was used to explore the ability of CB-M to induce gray mold resistance, and the results showed that CB-M preincubation enhanced the activities of su-peroxide dismutase, peroxidase, and catalase, accelerated the accumulation of pathogenesis-related proteins, flavonoids, and total phenolics, and increased the activities of beta-1,3-glucanase, chitinase, and phenylalanine ammonia-lyase during storage. These results indicated that CB-M is a good substitute for fungicides and has excellent prospects for controlling postharvest gray mold in horticultural crops.