Occurrence of Dry Rot and Associated Plant-Parasitic Nematodes in Early-harvested Yam Tubers

Abstract

Dry rot is a major constraint on the quality and commercial value of yam tubers in Côte d’Ivoire. This study assessed the occurrence and severity of dry rot and characterized the plant-parasitic nematodes associated with early-harvested yam tubers marketed in the country. A total of 1740 tubers representing five cultivars of the Dioscorea cayenensis-rotundata complex were examined across three agroecological zones. Dry rot prevalence and severity index were assessed, while nematodes were extracted from tuber peel, morphologically identified, and quantified. Dry rot occurred in tubers from all three zones. Tubers from the tropical dry savannah zone had the highest prevalence (31.20%), whereas the semi-deciduous dense forest zone had the lowest prevalence (9.10%). Among cultivars, Assawa had the highest dry rot prevalence (36.40%) and severity index (35.00%), while Krenglè had the lowest values. Three plant-parasitic nematode taxa were detected: Scutellonema bradys, Pratylenchus coffeae, and Meloidogyne sp. Scutellonema bradys was dominant, accounting for 99.87% of recovered nematodes. Its density was strongly and positively correlated with dry rot severity (r = 0.98; P < 0.001). These findings indicate marked variation in dry rot and S. bradys density among tuber origins and cultivars and provide a basis for further evaluation of cultivar responses, nematode population diversity, and integrated management strategies.