Objective The study aims to identify the species and dominant physiological races of Colletotrichum causing anthracnose in litchi in Maoming, and to evaluate the resistance of 28 main litchi cultivars grown locally to anthracnose, providing scientific basis for disease-resistant breeding and disease control.

Method The tissue separation method was used to isolate Colletotrichum from suspected diseased leaves and fruits collected from the National Litchi Germplasm Nursery (Maoming). Pathogen identification was conducted through morphological observation and multi-gene phylogeny analysis. Subsequently, an in vitro inoculation method was employed to inoculate the leaves and fruits of 28 main litchi cultivars with anthracnose. The resistance of various cultivars was evaluated by measuring the lesion area and disease index, and cluster analysis was conducted by Euclidean square distance intra-group association method.

Result Two species of Colletotrichum, totaling 8 strains, were successfully isolated and identified. Phylogenetic tree analysis showed that, among these strains, 6 were Colletotrichum siamense and 2 were C. fructicola, with strain LZTJ1 exhibiting the strongest pathogenicity. The in vitro inoculation conducted on leaves of 27 cultivars and fruits of 18 cultivars revealed that, 40.74% (11) and 50.00% (9) of the cultivars exhibited good resistance to anthracnose, respectively. Specifically, five highly resistant cultivars were identified from leaves inoculations, and three from fruits inoculations, with 'Yujinqiu', 'Baila' and 'Bingli' being resistant to both leaf and fruit infections. Additionally, it was found that different parts of the same cultivar showed different susceptibility, with fruits generally more sensitive than leaves. Through cluster analysis, the resistance of 17 litchi cultivars was divided into four categories, with 35.29% being resistant and most cultivars being susceptible.

Conclusion The study revealed the differences in the categories and pathogenicity of litchi anthracnose pathogens in Maoming area, and identified the resistance of local main litchi cultivars to anthracnose. The identified anthracnose-resistant cultivars such as 'Yujinqiu', 'Baila' and 'Bingli' can be used as important parent materials for future disease-resistant breeding.