Objective The aim of the study is to identify the pathogen causing leaf anthracnose on Ailanthus altissima in the Tianchishan National Forest Park in Songxian County of He'nan Province, China, so as to provide references for the prevention and control of the disease.

Method Pathogenic fungi were isolated from diseased leaves of A. altissima using tissue isolation methods. The isolates were purified in potato dextrose agar (PDA) by single spore culture. Species identifications for the pathogens causing anthracnose on A. altissima were carried out using morphological characterization, phylogenetic analysis, and pathogenicity assays.

Result A total of 11 Colletotrichum spp. isolates were recovered from the samples by tissue isolation methods. Colonies were white to gray in color with cottony mycelia and darker underneath on PDA, conidia cylindrical, hyaline, smooth-walled, aseptate. Two representative isolates (CH-1 and CH-3) were selected for pathogenicity tests and phylogenetic analyses. Both the isolates CH-1 and CH-3 were able to infect A. altissima in wounded inoculations. A multi-locus phylogeny was established based on five genomic loci ITS, ACT, TUB2, CHS-1 and GAPDH. The phylogenetic tree showed that the isolates CH-1 and CH-3 from A. altissima clustered into a clade with high confidence (bootstrap value, BP=99%), together with Colletotrichum fructicola.

Conclusion Based upon morphological characteristics and multi-locus phylogenetic analysis, the isolates CH-1 and CH-3 were identified as C. fructicola. This study represents the first report of C. fructicola on A. altissima in China.