Compositional shifts in fungal community of chestnuts during storage and their correlation with fruit quality

Chestnut (Castanea sativa Mill.) is an economically important fruit in Asia, Europe and America. The quality of which is greatly affected by postharvest fungal contamination. In order to understand how the fungal community impacts on fruit decay, we compared the composition of fungal community at different fruit parts (shell and kernel), between different cultivars, and between storage at normal state or after vibration treatment. The results showed the decay incidences increased with longer storage period and depended on cultivar and vibration treatment. Using a high-throughput sequencing (HTS), identified fungi can be clustered into 1116 operational taxonomic units (OTUs), representing 402 genera belonging to 8 phyla in this study. Members of the phylum Ascomycota were dominant in all samples and accounted for 92.6% of the total fungal species. Interestingly, the abundance and diversity of fungal communities on chestnut were decreased during storage period. At the genus level, Talaromyces, Peniophora, Colletotrichum, Candida and Penicillium were highly detected in “Dahongpao” chestnut from Luotian county (LT) samples; Alternaria, Penicillium, Botryosphaeria, Fusarium and Cladosporium were significantly detected in “Yanshanzaofeng (3113)” chestnut from Qianxi county (QX) samples. Linear discriminant effect size (LEfSe) and FUNGuild analysis demonstrated that beneficially saprotrophic fungi including Penicillium, Candida, Debaryomyces and various Saccharomyces appeared at the beginning of storage. At the later stage, pathogenic fungi became dominant, which containing Fusarium, Botryosphaeria, Colletotrichum, Neofusicoccum, Phialophora and Diaporthe. Furthermore, Canonical correspondence analysis (CCA) and heatmap analysis revealed that fruit decay incidence, malondialdehyde (MDA) content, and yeast and mold count (YMC) had significant positive correlation with the pathogen community, whereas activities of peroxidase (POD), polyphenol oxidase (PPO), and starch content were highly positive correlated with beneficial fungal community. These data could serve as biomarkers for better monitoring decay occurrence and developing an effective measurement to control postharvest chestnuts.