Anthracnose caused by Colletotrichum spp. is arguably the most serious postharvest disease of subtropical and tropical fruit crops in high rainfall production areas. Fungi within the C. gloeosporioides species complex, and to a lesser extent the C. acutatum species complex, have historically been reported as principal causal agents of anthracnose in many of these hosts. Recent taxonomic revisions of the genus Colletotrichum using molecular phylogenetic techniques have however delineated new species within these broad species complexes. Despite this, many Colletotrichum accessions held in Australian collections still remain to be verified by molecular methods.
Over 300 isolates of Colletotrichum species from a range of subtropical and tropical fruit hosts were selected for this study. DNA extracted from these isolates were subjected to sequencing of partial gene loci of ITS, TUB2, GAPDH, GS and CAL. A relatively high degree of heterogeneity was seen in accessions from avocado, lychee, papaya and passionfruit. These isolates were assigned to a number of different taxa including C. siamense, C. alienum, C. fructicola, C. queenslandicum, C. gloeosporioides, C. karstii, C. theobromicola, C. acutatum, C. simmondsii and C. fioriniae. Isolates from mango displayed a much lower degree of heterogeneity, and were mostly identified as C. asianum. All of the isolates from banana were C. musae. Species were also assigned to a limited number of isolates of Colletotrichum from rambutan, jackfruit, mangosteen, carambola and custard apple. Several putative new species were found that are the subject of ongoing taxonomic study.