Molecular re-identification of strains of the colletotrichum acutatum species complex deposited in the nias genebank and morphological characteristics of its member species

Abstract

Recently, nine phylogenetic groups were proposed for a plurivorous fungus, Colletotrichum acutatum by some researchers. Some of them were named as C. simmondsii, C. fioriniae, C. acutatum sensu stricto and C. carthami based on morphology and phylogenetic analyses of β-tubulin-2 gene partial sequences. We re-identified 170 strains deposited as C. acutatum in the NIAS Genebank, Japan based on phylogenetic analysis with the β-tubulin-2 gene sequences. Eighty strains with reddish colony colors and relatively uniform conidia belonged to C. fioriniae, 37 with a grayish to yellowish color and short conidia to C. simmondsii, 25 with a blackish to cream color and short conidia to C. carthami, 12 with a cream to pale orange color and narrow conidia to 'C. acutatum group A2-P' newly designated in this paper, 5 with a brownish to orange color and larger conidia to C. acutatum group A4, and 11 to other species of Colletotrichum. No strain of C. acutatum s. str. was found. A dichotomous key to the member species and groups was designated based on reverse colony color and conidial morphology. Because pathogenic strains of 18 host plants were re-identified, updating of pathogen names was proposed. Ten of them should be changed to C. fioriniae, and the pathogens of each five host plants such as strawberry and apple should be replaced with 2 to 3 species or the group. Sweet pepper pathogen was tentatively classified into C. acutatum group A2-P.