Food yams are important annual crops that yield root tubers. Virus diseases remain one of the major threats to their productivity, caused by a variety of viruses belonging to the Alphaflexiviridae (genus Potexvirus), Betaflexiviridae, Bromoviridae (genus Cucumovirus), Caulimoviridae (genera Badnavirus and Dioscovirus), Closteroviridae (genus Ampelovirus), Potyviridae (genera Macluravirus and Potyvirus), and Secoviridae (genus Sadwavirus) families. These viruses can lead to a range of symptoms, including mosaic, mottling, chlorosis, and other forms of leaf distortion and tuber quality degradation. A study was carried out to assess virus disease incidence and effect on pre-release yam genotypes. Two pre-release genotypes; TDr1500100 and TDr1500042, and a local cultivar (Amula) were tried in a Randomized Complete Block Design with 3 replicates. The sprouted seed yams were then left to virus infection under natural field conditions. Mean incidence of virus diseases was 46.9%. TDr1500042 had the lowest (43.7%) incidence while TDr1500100 was highest (51.9%). Mean fresh yam tubers differed significantly (P=0.05) between marketable and the unmarketable weights. TDr1500100 had highest (2.9 kg) tuber weight in plots while TDr1500042 had highest (1.00 kg) diseased yield. TDr15000100 indicated higher yielding potential and its resistance to virus diseases could thus be improved upon for adoption in the study area.

Keywords: Pre-released yam, Dioscorea spp., Virus diseases, southern Guinea Savanna, Tuber yield.