Plant-parasitc nematodes as important constraints for yam (Dioscorea spp.) production in West Africa: assessment of damage in tubers collected from fields, markets and stores.

Surveys were conducted to assessthe incidence of plant parasitic nematodes and associated damage to yam (Dioscorea spp.) tubers in fields, markets and stores in Benin and Nigeria. In Benin, 695 yam local accessions including 2500 tubersamples from 202 farmers’fields were visually assessed for typical nematode (Scutellonemabradys and Meloidogyne spp.) damage symptomsduring harvest period. In Nigeria, visual assessmentof nematodes was carried out on1141 yam heaps from 218 vendorsin different markets and 26 farmers’ stores located in the vicinity of the surveyed markets. Damage assessment of fields’ tubers showed significant variability inseverity and incidence of galls, cracking and dry rot symptom between accessions and between agroecological zones. Severity of tuber galling, cracking and dry rot symptom was scoredby up to5 over 5 for some accessions such as “Môrôkô”, “Wodjoa” and “Wôrgôninti”, respectively. Incidence was also high for many accessions such as “Tchaboulangapa” and Kabletona (100% for galling, cracking and dry rot symptom). The markets’ survey indicated an incidence of galling ranging from 52 % (Derived Savanna) to 59 % (Humid Forest), dry rot symptom from 17% (Southern Guinea) to 44% (Humid Forest) and tuber crackingbetween 4% (Southern Guinea) and7% (Derived Savanna). In the farmers’ stores, the gall incidence ranged from 22 % (Derived Savanna) to 27% (Southern Guinea) while the dry rot incidence was up to 9 % (Derived Savanna). The crack incidence varied from 1% to 3 % with the highest incidence recorded in the Derived Savanna. In addition, mixed nematode damagesymptoms were observed on yam tubers in fields,markets andfarmers’ stores.This study further established the evidence that nematodesare important constraints for yam production, suggesting that effective yam nematode management strategy is an urgent need for sustainable yam productionin West Africa.