Abstract
For an effective and efficient crop breeding program, collection of good genotypes that provides good agronomic background for the new variety to be developed must be available, and such genotypes must contain significant genetic variability for effective crop development. In order to determine the agronomic worth of a collection of sweetpotato genotypes so as to identify the superior ones under different agro-ecologies, and also to determine the extent of variability that exists among the genotypes, fifty-two genotypes were evaluated at Umudike (rainforest belt) and forty-eight at Otobi (humid guinea savannah) during the raining season using recommended protocols. While agronomic data were taken at 4 months after planting (MAP), sweetpotato virus disease (SPVD) incidence and severity scores were taken at 2 MAP. Results showed that significant (p<0.001) variation exists among the genotypes for all the traits except weight of unmarketable roots in both locations. Genotype PYT/12/074 had the highest root yield of 29.33 t/ha at the rainforest belt followed by Solo-2 and PYT/12/105 with yield levels of 27.67 and 26.33 t/ha, respectively. At Otobi, same PYT/12/074 had the highest root yield of 27.74 t/ha followed by Kwara and PYT/12/105 with yield levels of 27.67 and 26.33 t/ha, respectively. The principal component analysis identified marketable root weight, number of marketable roots, SPVD incidence and severity as the most important traits that influenced the observed variation among the genotypes. The biplot analysis further identified most of the orange-fleshed genotypes as highly susceptible to SPVD. Genetic studies of the traits showed that while broad-sense heritability estimates ranged from moderate to high for the important agronomic and SPVD traits, the high GCV and genetic advance observed portends a high genetic gain and good breeding progress in the breeding program using the genotypes.
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