Molecular and Morpho-cultural Characterization of Colletotrichum gloeosporioides Causing Grape Anthracnose

Abstract

Grape (Vitis vinifera L.) is an economically important fruit crop, and anthracnose can adversely affect vine growth, berry yield, and fruit quality. The present study characterised eleven isolates of Colletotrichum gloeosporioides collected from grape-growing districts of Northern Karnataka using morpho-cultural and molecular approaches. On potato dextrose agar, the isolates showed variation in colony colour, pigmentation, growth pattern, sectoring, conidial dimensions, and sporulation intensity. Colony colour ranged from white-grey to grey-white, and pigmentation varied from light orange to dark brown. Most isolates exhibited fluffy growth with regular margins, while sectoring was observed in Cg-1, Cg-3, Cg-4, Cg-5, and Cg-6. The isolates produced septate, hyaline mycelium and oblong, unicellular conidia with a single oil globule. Mean conidial dimensions ranged from 11.44 × 5.65 µm to 15.81 × 5.81 µm, with sporulation ranging from moderate to excellent. PCR amplification of the internal transcribed spacer region and species-specific markers produced amplicons of approximately 550 bp and 450 bp, respectively. Sequence comparison showed high similarity with reference sequences of C. gloeosporioides. Phylogenetic analysis of three representative isolates placed them within the C. gloeosporioides clade, consistent with the morphological observations and species-specific PCR results. These findings document morpho-cultural variability among the isolates and support their molecular identification as C. gloeosporioides.