Unravelling Species Diversity and Pathogenicity of Colletotrichum Associated with Anthracnose on Osmanthus fragrans in Quanjiao, China

Abstract

Osmanthus fragrans is a popular ornamental tree species known for its fragrant flowers and is widely cultivated in Asia, Europe, and North America. Anthracnose is a disastrous threat to the growth and development of O. fragrans and has caused significant economic losses. To reveal the potential pathogen diversity of anthracnose, 127 isolates of Colletotrichum were isolated from the symptomatic leaves. Morphological studies and multilocus phylogenetic analyses with the concatenated sequences of the internal transcribed spacer, glyceraldehyde-3-phosphate dehydrogenase, chitin synthase, actin, beta-tubulin, calmodulin, and the intergenic region between Apn2 and Mat1-2-1, as well as a pairwise homoplasy index, test placed the causal fungi as two new species, Colletotrichum anhuiense (two isolates) and C. osmanthicola (12 isolates), and three known taxa, C. fructicola (18 isolates), C. gloeosporioides (62 isolates), and C. karstii (33 isolates). Among them, C. gloeosporioides was the most dominant, and C. anhuiense was occasionally discovered from the host tissues. Pathogenicity tests in vivo on O. fragrans leaves revealed a significant difference in virulence among these species. Of them, C. gloeosporioides, C. osmanthicola, and C. anhuiense were significantly more virulent than C. fructicola and C. karstii, while C. karstii was the least virulent. To our knowledge, this study was the first to report the pathogen diversity of anthracnose on O. fragrans.