Identification of Fungal Pathogens of Chinese Chestnut Fruit Rot and Analysis of Resistance Differences Among Major Cultivars

This study aimed to identify fungal species causing fruit rot of chestnut (<i>Castanea mollissima</i> Blume) in Hebei Province, China and analyze the resistance differences among major cultivars. A total of 220 fungal isolates were obtained from healthy and diseased kernels, which were classified into six distinct genera: <i>Diaporthe</i> (48.6%), <i>Talaromyces</i> (22.3%), <i>Alternaria</i> (10.5%), <i>Mucor</i> (9.5%), <i>Fusarium</i> (5.5%), and <i>Rhizopus</i> (3.6%). Based on both morphological and molecular analyses, six representative isolates of the six genera were identified as <i>Diaporthe eres</i> Nitschke, <i>Talaromyces rugulosus</i> Samson, N. Yilmaz, Frisvad & Seifert, <i>Alternaria alternata</i> (Fr.) Keissl., <i>Mucor circinelloides</i> Tiegh., <i>Fusarium proliferatum</i> (Matsush.) Nirenberg, and <i>Rhizopus stolonifer</i> (Ehrenb.) Vuill. Among these, <i>D. eres</i> was first reported to cause fruit rot on <i>C. mollissima</i> in China. Moreover, disease resistance evaluation of major cultivars showed significant differences: YG, YSSF, and DBH exhibited strong resistance under both natural conditions (with 1.67% to 5.27% DI after 180 days storage) and artificial inoculation (with 32.96 ± 0.64 to 52.61 ± 0.55 DI); while YJ was highly susceptible (with 47.71% decay incidence and 70.50 ± 7.22 DI). Correlation analysis revealed that the disease index was negatively correlated with sucrose and sorbitol contents, but positively correlated with stachyose and fructose contents. This study advances the understanding of postharvest chestnut fruit rot and provides a theoretical basis for breeding resistant cultivars and developing control strategies to mitigate losses and ensure food safety.