LAUSR

Leaf spot is a common and serious disease of sweet cherry worldwide and has become a major concern in China. From 2018 to 2020, disease investigations were carried out in Beijing City, Sichuan, Shandong and Liaoning Provinces in China, and 105 Colletotrichum isolates were obtained from diseased samples. Isolates were identified by morphological characterization coupled with multi-gene phylogenetic analyses based on six loci (internal transcribed spacer region, glyceraldehyde 3-phosphate dehydrogenase, calmodulin, actin, chitin synthase and β-tubulin). A total of 13 Colletotrichum species were identified, namely: Colletotrichum aenigma, C. gloeosporioides, C. fructicola, C. siamense, C. temperatum, C. conoides, C. hebeiense, C. sojae, C. plurivorum, C. karsti, C. truncatum, C. incanum and C. dematium. Among these, C. aenigma (25.7%) was the most prominent species isolated from diseased leaves, followed by C. gloeosporioides (19.0%) and C. fructicola (12.4%). Pathogenicity was tested on detached leaves of cv. 'Tieton' and 'Summit', and young seedlings of cv. 'Brooks' under greenhouse conditions. All 13 species were pathogenic to cherry leaves, and C. aenigma, C. conoides and C. dematium showed high levels of virulence. Seedlings inoculated with the isolates developed similar symptoms to those seen in the orchards. This study provides the first reports for 11 of the 13 Colletotrichum species on sweet cherry in the world, except for C. aenigma and C. fructicola. This is the first comprehensive study of Colletotrichum species associated with cherry leaf spot in China and the results will provide basic knowledge to develop sustainable control measures for cherry leaf spot.