Genotype x Environment and Stability Analysis of Oil Content in Sesame (Sesamum indicum L.) Evaluated Across Diverse Agro-ecologies of the Awash Valleys in Ethiopia

Aim: To estimate the nature and magnitude of GEI interaction for oil content in sesame varieties and to identify stable and promising varieties for general and specific adaptations across the areas of the Awash valleys in Ethiopia.

Study Design: Entries were planted in a randomized complete block design (RCBD) replicated thrice in each location and year.

Place and Duration of Study: The study was conducted at Assaita, Melkassa and Werer representing the Lower, Upper and Middle Awash valleys of Ethiopia respectively, during the 2010/11 main cropping season and 2011/12 off season.

Methodology: Morphological data taken from each environment were analyzed for combined analysis of variance, Additive Main Effects and Multiplicative Interaction (AMMI), Biplot analysis, AMMI Stability Value (ASV), and regression analysis. Finally, ranking of genotypes was done based on the overall results of all stability indices.

Results: Combined analysis of variance showed highly significant (P<0.01) difference between the varieties, environments and GEI, suggesting differential response of varieties across testing environments and the need for stability analysis. Proportion of variance captured by environments was 1.43%, genotypes 91.5% and GEI 7.1% of the total variation, indicating less effect of environments on oil content as compared to the effect of genotypes. Stability analysis by AMMI and Joint-regression model were used to further shed light on the GEI of oil content. Two IPCA of AMMI were significant (P<0.01) and captured the largest portion of variation of the total GEI, which indicated that the AMMI model was the best for the data set. The Joint regression analysis indicated that the linear regression (bi) did not deviate from unity for all varieties, suggesting that performance of the cultivars could not be predicted in a linear manner.

Conclusion: The influence of environment is less prominent in the manifestation of oil content along the areas of Awash valleys. Season two is the best environment for growing the present set of genotypes for oil content. Variety Adi was identified as the most stable variety across environments for oil content. This variety can be recommended for varied environments of the Awash valleys to exploit its yield potential. The rest high yielder varieties, Serkamo, Tate and Argene can be adapted only under favorable environmental conditions