Prevalence of yam nematodes in diverse soil communities, and their morphometrics in the Krachi-Nchumuru District of Ghana

Abstract

Yam (Dioscorea spp.) is susceptible to dry rot disease, which limits its yields in farmers fields in West Africa.The objective of this study was to assess the occurrence and characteristics of the plant-parasitic nematode (Scutellonema bradys) on yam from the Volta Region of Ghana. A survey was conducted in KrachiI-Nchummuru District in the Volta region in Ghana, using a semi-structured questionnaire in ten communities. Majority of the farmers (62%) were unaware of nematodes and their damage caused to yam. Most interviewees (84%) mentioned the ‘pona’ yam variety as the most susceptible genotype to rot, especially in storage. Twelve nematode genera were identified in soils, and eight under storage conditions. Soil samples had, for relative abundance, 31.5% of nematodes as Scutellonema bradys and 16.8% as Meloidogyne spp. On the other hand, relative abundances in yam peels for S. bradys, Meloidogyne spp. and Pratylenchus spp. were 88.4, 6.0 and 3.3%, respectively. Body lenghts of female S. bradys ranged from 747.3 to 861.9 um. There was a strong positive correlation between tail length and head region diameter (r = 0.81); and stylet knob height and vulva position (r= 0.68). Agglomerative hierarchical clustering (AHC) showed 5 major groups at a dissimilarity of 90%, with sub-groups formed at dissimilarity value of 50%. In-depth survey of communities in the Krachi Nchumuru district revealed that, Scutellonema bradys is a threat to yam production in this region, and results in considerable dry rot disease and yield losses.