Identification, Characterization, and Population Structure of Colletotrichum spp. Causing Grape Ripe Rot in China

Grape ripe rot, a globally significant fungal disease caused by Colletotrichum spp., severely threatens grape yield and quality. This study systematically investigated the pathogen species, biological characteristics, and fungicide sensitivity through multiregional sampling (2022 to 2024, covering seven districts across four provinces), morphological analysis, molecular identification, and EC 50 assays. The results revealed that 125 isolates were obtained and classified into five species, namely, Colletotrichum aenigma, C. conoides, C. viniferum, C. gloeosporioides, and C. fructicola, based on morphological traits and multilocus phylogenetic analysis (ITS, CHS, GAPDH, TUB2, and ACT). Among these, C. viniferum was identified as the dominant species responsible for grape ripe rot, with an isolation rate of 74.4%, and C. conoides represents a new species isolated from grape ripe rot in China. Biological assays revealed that the optimal temperature and pH for mycelial growth on PDA were 25 to 30°C and pH 5 to 6, respectively, and the pathogenicity significantly increased at 30°C following wound inoculation. Fungicide sensitivity tests indicated that prochloraz exhibited the highest inhibitory efficacy against all the species (EC 50 ≤ 0.03 mg/liter). This study elucidates the geographical distribution patterns of Colletotrichum spp. in China and their differential responses to fungicides, providing critical theoretical and practical insights for optimizing integrated management strategies against grape ripe rot.