morphological and pathological characterisation of colletotrichum sp. as casual agent of anthracnose in dioscorea sp.

Colletotrichum gloeosporioides and Colletotrichum dematium strains were isolated from yam plants in the Sucre depart-ment. Macro- and microscopic descriptions were made, finding that the predominant colour for the colonies was light purple. Sporulation was higher than 58,000 conidia/ml for most colonies. Growth rate lay within a range of 4 to 5mm/day. C. gloeosporioide isolate conidial morphology revealed a cylindrical spore having one rounded end whilst the other was acute shaped. Conidia length and width averaged between 7-8 micras and 3-4 micras, respectively. C. dematium colonies, however, were characterised by being grey and having radial growth. The fálcate and fusiform conidia tapered at the acute apex. They had a length and width of 16-18 micras and 3-4 micras, respectively. C. gloeosporioides colonies showed different macroscopic morphology but similar microscopic characteristics. Vegeta-tive compatibility was evaluated amongst different geographical isolates resulting in 90% compatibility. A patho-genic assay was done for evaluating isolate virulence on tolerant and susceptible cultivars. The isolates showed great variability regarding their virulence. The Colletotrichum isolate collection represents a tool for use in molecular characterisation and evaluating yam germplasm tolerance to this pathogen. Keywords: Colletotrichum, yam, anthracnose, phytopathology.