Morphological Characteristics of Scutellonema bradys Populations Responsible for Yam Dry Rot in Côte d’Ivoire

The great diversity of agroecological factors that cover the yam production area in Côte d’Ivoire can be a source of morphological variability within Scutellonema bradys species, responsible for yam dry rot. This study aims at identifying the morphological group(s) of S. bradys which infect(s) yam Dioscorea cayenensis-rotundata. Two hundred ten yam tubers for sale in food markets in the Autonomous District of Abidjan were sampled from traders. After extraction and identification, a morphological characterization was carried out on S. bradys populations using morphological descriptors. Yam tubers sampled from food markets came from three agroecological zones namely dry tropical savannah, semi-deciduous dense forest and transitional forest areas. Morphometric variables and ratios used individually did not help identify morphological groups. Principal component analysis, however, performed with the most discriminating variables and ratios revealed three morphological groups named "large", "medium" and "small" in males and females and confirmed by the agglomerative hierarchical clustering. Each group consisted of a rate greater than 48% of individuals from a given agroecological zone. Three morphological groups of S. bradys are associated with yam dry rot in Côte d’Ivoire. Pathogenic and molecular characterization of the morphological groups would be necessary with a view to researching control methods.