First report of anthracnose caused by Colletotrichum fructicola on Brassica parachinensis in China

Anthracnose caused by Colletotrichum species is a devastating disease on Brassica parachinensis which affect the crop production and cause economic losses in China. During the period from 2012 through 2018, samples of diseased leaves of B. parachinensis showing anthracnose-like symptoms, that is irregular and slightly sunken lesions in gray to brown color with or without small black spots symptoms were collected in open fields of B. parachinensis from 11 prefecture-level cities of Guangdong province in southern China. One hundred and two isolates of Colletotrichum were obtained from single spore cultures. Based on cultural and morphological characteristics, 86 and 13 isolates were identified as C. higginsianum and C. truncatum, respectively. However, other three isolates were morphologically different from C. higginsianum and C. truncatum, but similar to C. fructicola. To confirm the identification, the internal transcribed spacer (ITS) region, actin (ACT), chitin synthase 1 (CHS1), glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and beta-tubulin (TUB2) genes were amplified. Phylogenetic analysis showed that the ITS, ACT, CHS1, GAPDH and TUB2 sequences of these three isolates clustered with sequences belonging to the ex-type strain ICMP 18581 of C. fructicola with a posterior probability value of 1. Pathogenicity assays showed that all these three isolates could infect healthy leaves, stems and flowers of B. parachinensis and cause typical leaf and stem rot symptoms originally observed and also flower rot symptoms that rarely occurred on B. parachinensis in the fields. The same pathogen was re-isolated from lesions of inoculated plants. Distribution investigation showed that C. higginsianum is widely distributed and is the major pathogen causing anthracnose of B. parachinensis in Guangdong. C. fructicola and C. truncatum distributed across through the north to the south regions and through the east to the west regions of Guangdong, respectively. To our knowledge, this is the first report of C. fructicola as a causal agent of anthracnose on B. parachinensis in China.