Characterisation of Colletotrichum Species Causing Anthracnose on Yam (Dioscorea rotundata) in Benue and Nasarawa States, North Central Nigeria

Anthracnose of yam (Dioscorea rotundata) caused by Colletotrichum species is a significant pre- and post-harvest disease in North Central Nigeria, contributing to stand loss, reduced tuber yield, and post-harvest quality deterioration. Despite the importance of anthracnose in yam production systems, the taxonomic identity of Colletotrichum species causing yam anthracnose in Benue and Nasarawa States has not been rigorously established using multi-locus molecular methods. This study characterised Colletotrichum isolates collected from 76 yam plants displaying anthracnose symptoms across both states, using a multi-locus phylogenetic approach incorporating ITS, ACT, TUB2, CHS-1, and GAPDH gene regions. Morphological characterisation, growth rate analysis, and pathogenicity assays on detached yam leaf and tuber tissue complemented the molecular work. Multi-locus phylogenetic analysis resolved isolates into three species: Colletotrichum gloeosporioides sensu stricto, C. truncatum, and a putatively novel Colletotrichum lineage nested within the C. gloeosporioides species complex. The putative novel taxon, provisionally designated Colletotrichum sp. nov. YAM-NC1, was recovered from 22 percent of isolates and was characterised by distinctively slow growth and elevated virulence on tuber tissue in comparison to described species. All three taxa produced visible anthracnose lesions in inoculation assays. These findings resolve a significant taxonomic gap in Nigerian yam pathology literature and provide the molecular reference framework necessary for developing species-specific management and breeding resistance strategies. Keywords: Colletotrichum, yam anthracnose, multi-locus phylogeny, North Central Nigeria, species characterisation.