Identification and biological characteristics of <i>Colletotrichum</i> species causing persimmon anthracnose in China and screening of <i>Colletotrichum horii</i> antifungal agents

Persimmon anthracnose, caused by a diverse range of Colletotrichum species with genetic variations, poses a significant and widespread threat to persimmon cultivars. This study aimed to identify the causal agents via morphological characterization and multi-locus phylogenetic analysis, investigate their biological characteristics, and evaluate the efficacy of antifungal agents against the most virulent species. Six anthracnose isolates were identified: C. boninense, C. fioriniae, C. horii, C. gloeosporioides s.s, C. fructicola, and C. aenigma. All isolates were pathogenic to persimmon branches and leaves, with C. horii causing the largest leaf lesions and exhibiting strong pathogenicity on branches, resulting in severe infections on persimmon seedling leaves and branches. Beyond determining the pathogenicity of these Colletotrichum spp. on persimmons, this study also investigated the biological characteristics of the six anthracnose fungi, including optimal growth conditions for temperature, pH, light, and medium. The results showed that the optimal temperature for the growth of all six fungi was 25 °C, with no significant variation in the pH values ranging from four to ten. Light conditions significantly influenced sporulation: continuous darkness was most conducive to conidial formation and production, except for C. boninense. Mycelial growth of most species was insensitive to light, while C. boninense grew fastest under continuous light. In vitro screening of sixteen antifungal agents against C. horii revealed that Bacillus subtilis exhibited the strongest inhibitory activity against mycelial growth, followed by carbendazim, imidazole, thiophanate-methyl, pyraclostrobin, and difenoconazole. Field trials confirmed that imidazole, pyraclostrobin, and difenoconazole provided the most effective control of persimmon anthracnose. These findings provide a theoretical basis for understanding the epidemiology and developing management strategies for persimmon anthracnose.