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 southern and eastern zones of Tigra, Ethiopiay in 2012 to evaluate their total root yield potential. Randomized complete block design with three replications was used for the experiment Yield data was analyzed using 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 locations 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 Kukufto testing location while the inferior (13.45 t/ha) was at Rarhe. Similarly, among the genotypes, LO gave the highest mean total root yield (30.9 t/ha), while bellela gave the lowest (7.78 t/ha). The AMMI analysis for the total storage root yield also showed highly significant difference for genotypes, locations and the genotypes by locations interaction components The contribution of genotype, location 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 largely due to the inheritance of genotype effect. The genotype by location interaction was further partitioned using 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 best testing location and LO, Tulla and Kulfo as best genotypes for south and south east zones of Tigray region.