Evaluation of Sweet Potato (Ipomea batata l.) Varieties for Total Storage Root Yield in South and South East Zones of Tigray, Ethiopia

Seven sweet potato varieties (Bellela, Kabode, Kulfo, LO, Temesgen, Tulla, and Vitae) were tested in the southern and eastern zones of Tigra, Ethiopia, in 2012 to evaluate their total root yield potential. A randomized complete block design with three replications was used for the experiment Yield data was analyzed using a combined ordinary analysis of variance and the additive main effect and multiplication interaction effect model (AMMI). The combined analysis of variance across locations showed significant variation among genotypes, locations, and the genotypes by location interaction for the total storage root yield (t/ha). Based on this, the superior mean total root yield (26.82 t/ha) was obtained at the Kukufto testing location, while the inferior (13.45 t/ha) was Rare. Similarly, among the genotypes, LO gave the highest mean total root yield (30.9 t/ha), while belle la gave the lowest (7.78 t/ha). The AMMI analysis for the full storage root yield also showed highly significant differences for genotypes, locations, and the genotypes by location interaction components. The contribution of genotype, site, and genotype by location interaction to the total variation in root yield was about 54.1%, 21.4%, and 19.4%, respectively. The genotype main effect contributed more to the total variability indicating that the variation was mainly due to the inheritance of the genotype effect. The genotype by location interaction was further partitioned using the AMMI model, and the first two principal components explained 100% of the total variability. The model captured 83.4 % of the interaction sum of squares with the first Interaction Principle Component Axis (IPCA) (in 58.3% of the interaction degrees of freedom) and 16.6% by the second IPCA axis (with 41.7% of the G x E d.f). AMMI biplot view of this study identified kukufto as the best testing location and LO, Tulla, and Kulfo as the best genotypes for the south and southeast zones of the Tigray region.