Diversity of Colletotrichum species causing anthracnose on three oak species ( Quercus acutissima , Q. mongolica and Q. variabilis ) in China

Abstract Anthracnose of oak ( Quercus ) caused by Colletotrichum spp. is one of the most common diseases in oak forests. To investigate the species diversity of Colletotrichum associated with oak anthracnose, symptomatic leaf samples of three oak species ( Q . acutissima , Q . mongolica and Q . variabilis ) were collected from Anhui, Hainan, Henan, Shaanxi and Shandong Provinces, Inner Mongolia Autonomous Region, and Beijing City in China from 2019 to 2022. A total of 219 Colletotrichum isolates were obtained and identified by morphological and phylogenetic analyses of the rDNA internal transcribed spacer (ITS), glyceraldehyde‐3‐phosphate dehydrogenase ( gapdh ), chitin synthase 1 ( chs‐1 ), actin ( act ) and β‐tubulin ( tub2 ) sequences. Nine species were identified: C . fioriniae (two isolates, 0.9%), C . camellia‐japonicae (two isolates, 0.9%), C . karstii (three isolates, 1.4%), C . quercicola (two isolates, 0.9%), C . aenigma (three isolates, 1.4%), C . endophyticum (two isolates, 0.9%), C . fructicola (68 isolates, 31.1%), C . gloeosporioides sensu stricto (74 isolates, 33.8%) and C . siamense (63 isolates, 28.8%). Pathogenicity was confirmed using Koch's postulates, which showed that five species ( C . camellia‐japonicae , C . endophyticum , C . fructicola , C . gloeosporioides s. s. and C . siamense ) caused Q . acutissima anthracnose, four species ( C . karstii , C . fructicola , C . gloeosporioides s. s. and C . siamense ) caused Q . mongolica anthracnose and six species ( C . fioriniae , C . quercicola , C . aenigma , C . fructicola , C . gloeosporioides s. s. and C . siamense ) caused Q . variabilis anthracnose. This study demonstrates the pathogenic species diversity of Colletotrichum on Q . acutissima , Q . mongolica and Q . variabilis .