Morphological and pathological characterization of Colletotrichum species causing anthracnose of litchi leaves in Guangxi, China

Litchi (Litchi chinensis Sonn.) is an evergreen subtropical fruit tree native to southern China. Litchi is vulnerable to a wide range of diseases affecting yield and fruit quality. Anthracnose is one of the main diseases during the period of growth and storage, which has a serious impact on the quality and production of litchi. In December 2020 to May 2021, typical anthracnose symptoms were observed on litchi leaves in different orchards in Qinzhou City, Guangxi Province, Southern China. According to colony features, conidial and appressorial morphology, and sequence analysis of several genomic regions (internal transcribed spacer (ITS) region, chitin synthase (chs-1), actin (act), calmodulin (cal), glyceraldehyde-3- phosphate dehydrogenase (gapdh), beta-tubulin (tub2) and the intergenic region of apn2 and MAT1-2- 1 (ApMat)), 44 isolates were obtained, and 26 were identified as three Colletotrichum species: C. fructicola (50%), C. siamense (42.31%), C. gigasporum (7.69%). The pathogenicity tests were performed with conidial suspension and mycelia plugs to inoculate wounded litchi seedlings. The results of pathogenicity tests showed that the virulence of C. gigasporum was the weakest, and the virulence of C. fructicola was the strongest. This is the first report of C. gigasporum causing anthracnose of litchi worldwide.