Molecular re-identification of strains in NIAS Genebank belonging to phylogenetic groups A2 and A4 of the Colletotrichum acutatum species complex

INTRODUCTION An anthracnose pathogen, Colletotrichum acutatum J.H. Simmonds is known as a plurivorous and cosmopolitan fungus. Since it was first described to have fusiform conidia and reddish colonies in Australia (Simmonds, 1965), its distribution, host plants, macroscopic and microscopic morphology have been reported to vary in the extreme (Aa, et al., 1990; Sato, 1997; Sato et al., 1998; Vinnere et al., 2002). A ‘larger spored form’, which Simmonds (1965) described in the first report, appeared to be one of the morphologically distinct groups of C. acutatum. Because some strains of the fungus that are pathogenic to anemone were morphologically similar to Colletotrichum gloeosporioides (Penzig) Penzig & Saccardo, they were misidentified as the latter in Japan (Sato et al., 1996). Recently, several researchers recognized genetic groups A1 to A8 within the species based on sequences of the ribosomal DNA internal transcribed spacer region (rDNA-ITS) (Johnston & Jones, 1997; Lardner et al., 1999; Vinnere et al., 2002; Sreenivasaprasad & Talhinhas, 2005). Group A9 was added based on randomly amplified polymorphic DNA polymerase chain reaction (RAPD-PCR) and b -tubulin-2 (TUB2) gene partial sequences (Whitelaw-Weckert et al., 2007). Some of the researchers proposed dividing the groups into d i s t i n c t s p e c i e s ( G u e r b e r e t a l . , 2 0 0 3 ; Sreenivasaprasad & Talhinhas, 2005; Vinnere et al., 2002), indicating that C. acutatum sensu lato is a typical species complex. Colletotrichum fioriniae (Marcelino & Gouli) R.G. Shivas & Y.P. Tan (=group A3) and Colletotrichum simmondsii R.G. Shivas & Y.P. Tan (=group A2, A9) were separated from the C. acutatum species complex and also defined C. acutatum sensu stricto (=group A5) based on their morphological characteristics in culture and molecular phylogenetic analyses of the ITS region and the b -tubulin-2 gene sequences (Shivas & Tan, 2009). Colletotrichum carthami (Fukui) S. Uematsu, Kageyama, Moriwaki & Toy. Sato was revived as a member of the species complex. This species had distinct b -tubulin-2 gene sequences and specific pathogenicity for asteraceous plants (Uematsu et al., 2012). Although each of the three species except for C. carthami was reported to have characteristic colony color (Shivas & Tan, 2009; Uematsu et al., 2012), differences in microscopic morphology of the four species were still unclear. Quite recently, the species complex was split into 29 species based on phylogenetic studies with the 5.8S nuclear ribosomal gene including the two internal transcribed spacers (ITS), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), chitin synthase 1 (CHS-1), histone 3 (HIS3), actin (ACT) and TUB2 gene sequences of 331 strains (Damm et al., 2012). Twelve of the 29 species were separated from group A2 and Colletotrichum godetiae Neergaard was assigned to the monophyletic group A4. All of the member species including 21 new ones that have been studied in culture were characterized morphologically (Damm et al., 2012). On the other hand, 170 strains deposited as C. acutatum in the NIAS Genebank, Japan were re-identified as C. fioriniae, C. simmondsii, C. carthami, C. acutatum group A2-P, group A4 and other species of the C. acutatum species complex based on phylogenetic analysis with TUB2 (Sato et al., 2013). Morphological differences such as colony color, conidial shape and size of each *Corresponding author E-mail: s1043@affrc.go. jp Molecular re-identification of strains in NIAS Genebank belonging to phylogenetic groups A2 and A4 of the Colletotrichum acutatum species complex