Colletotrichum shisoi sp. nov., an anthracnose pathogen of Perilla frutescens in Japan: molecular phylogenetic, morphological and genomic evidence.

Species of the fungal genus Colletotrichum are among the most devastating pathogens of agricultural crops in the world. Based on DNA sequence data (ITS, GAPDH, CHS-1, ACT, TUB2) and morphology, we revealed Colletotrichum isolates infecting the oil crop Perilla frutescens, commonly known as shiso, to represent a previously unknown species of the C. destructivum species complex and described it as C. shisoi. We found that C. shisoi appears to be able to adopt a hemibiotrophic lifestyle, characterised by the formation of biotrophic hyphae followed by severe necrotic lesions on P. frutescens, but is less virulent on Arabidopsis, compared to its close relative C. higginsianum which also belongs to the C. destructivum species complex. The genome of C. shisoi was sequenced, annotated and its predicted proteome compared with four other Colletotrichum species. The predicted proteomes of C. shisoi and C. higginsianum, share many candidate effectors, which are small, secreted proteins that may contribute to infection. Interestingly, C. destructivum species complex-specific secreted proteins showed evidence of increased diversifying selection which may be related to their host specificities.