Antifungal activity and mechanism of chaetoglobosin D against Alternaria alternata in tomato postharvest storage

The postharvest decay of tomatoes, induced by the pathogen Alternaria alternata during storage, has led to significant economic losses in the tomato industry. This study aimed to explore the effect and underlying mechanism of the marine-derived fungus bioactive compound chaetoglobosin D (ChD) against postharvest black spot disease in tomato fruit. In both in vitro and in vivo experiments, ChD was found to effectively inhibit the growth of A. alternata and reduce the lesion area caused by this pathogen. Electron microscopy observations revealed that ChD induces mycelia morphological deformations, increases branching, and disrupts the integrity of cell membrane and certain organelle. Enrichment analysis of transcriptome revealed a notable enrichment of genes associated with oxidoreductase activity and ATPase activity. Similarly, analysis of metabolome showed significant changes in glycerophospholipid metabolism, the pentose phosphate pathway, and the citrate cycle. These findings were further supported by fluorescence staining, increased relative conductivity, ergosterol, malondialdehyde, and hydrogen peroxide content, as well as decreased catalase, superoxide dismutase, ATPase activity, and ATP content. These results suggested that ChD could impact the synthesis of cell membranes, leading to oxidative damage within the mycelia. The application of ChD in preserving fresh tomatoes effectively maintained the quality and flavor of the product, positioning it as a natural agent for mitigating postharvest decay in tomatoes.