Fluctuation in Yam Nematodes Depending on the Phenological Stages of the Main Yam Species (Dioscorea alata L.) Cultivated in Côte d’Ivoire

Abstract

The telluric factors favorable to nematode pathogenic diversity make yam nematode control ineffective. This work aims at studying the fluctuation in yam nematodes depending on yam phenological stages. Trials were implemented in four yam production areas in Côte d'Ivoire. After inventory of symptoms on yam tubers, the nematodes associated with the symptoms were extracted and identified. The correlation coefficients between the severity of symptoms on tubers and the size of the associated nematode populations were determined. The size of nematode populations associated with the symptoms were determined in 100 g of soil and 100 g of yam peel were determined depending on the phenological stages of yam plants. Galls, cracks, dry and wet rot were observed on harvested yam tubers. Globodera, Meloidogyne spp., Pratylenchus coffeae and Xiphinema were the nematodes associated with the symptoms. Pratylenchus coffeae was strongly involved in the development of cracks (r = 0.75) and dry rot (r = 0.86) then Meloidogyne spp. in that of galls (r = 0.78). Pratylenchus coffeae and Meloidogyne spp. fluctuation in cultivation soils and yam tubers is influenced by yam phenological stages. Their numbers increase in soils and tubers before tuberization initiation. Producers could draw on the results of this study to establish a schedule of nematicide treatments that could start as soon as yam seeds are planted.