Genetic Gain in Grain Yield Potential and Associated Traits of Sesame (Sesamum indicum L.)

Abstract

A yield potential experiment was conducted with eleven sesame varieties developed by the then Ethiopian Lowland Oil Crops Research Program from 1960s to 2007 along with one local variety. The objectives were to understand the genetic gain made in grain yield potential and to assess changes produced on morphological traits associated with genetic yield potential improvement. The varieties were evaluated in a randomized complete block design (RCBD) with three replications in 2010 main cropping season under irrigation and rainfed conditions at Melka Werer Agricultural Research Center and Mieso experimental testing sites, respectively. The analysis of variance revealed significant differences among varieties for all investigated traits. The over all increase in grain yield of improved varieties over the local variety  was estimated to be 150.3 kg ha^-1 (26.03%). Based on the regression analysis, the estimated average annual rate of increase in grain yield potential was 9.55 kg ha^-1 year^-1 with an annual relative genetic change of 1.24 % year^-1. Harvest index and seed yield per plant showed significant and non significant increase with respective annual genetic gains of 3.00 and 0.57% respectively, while biomass yield, plant height, and number of capsules per plant showed insignificant decrease of 0.64, 0.10 and 0.17% per annum respectively. Days to flowering and days to maturity decreased non significantly by 0.33 and 0.26%, while seed growth rate and seed yield per day increased significantly by 1.35 and 1.74% per annum, respectively. Absence of plateau indicated the potential for further progress in grain yield in sesame. Correlation analysis indicated that grain yield was positively correlated with harvest index, plant height, seed yield per plant, number of capsule per plant, capsule length, thousand seed weight, seed growth rate and seed yield per day while, biomass yield, number of branches per plant, days to flowering, days to maturity and capsule filling period were negatively correlated with yield. The stepwise regression analysis showed that seed yield per plant greatly contributed to the variation among the varieties in grain yield. Improvement for high grain yield potential in sesame occurred over the past 47 years was ,due to grain yield improvement efforts. However, the improvement was also associated with paralleled increase in harvest index, plant height, seed yield per plant, number of capsule per plant, capsule length, thousand seed weight, seed growth rate and seed yield per day.

Keywords: Ethiopia, Harvest index, Seed yield, Yield components, Yield gain.