RELATIONSHIP BETWEEN GRAIN YIELD AND YIELD COMPONENTS OF THE ETHIOPIAN DURUM WHEAT GENOTYPES AT VARIOUS GROWTH STAGES

Abstract

Water availability is the main constraint limiting durum wheat production in many parts of the world. Knowledge of the phenotypic and genotypic relationship between grain yield and its various components is an important step in developing selection criteria under water stress environment. To assess the usefulness of some of the agronomic traits as indicators of grain yield, eighteen durum wheat genotypes were evaluated under water stress treatments induced at three growth stage together with a well-watered control in plastic pots during 2006/07 growing season. The water stress treatments used were continuous stress from tillering to physiological maturity (M1), stress from anthesis to physiological maturity (M2) and stress from grain-filling stage to physiological maturity (M3). The water levels were maintained in the range of 35-50% field capacity in the stress treatments while above 75% in the control treatment. Harvest index and grain-filling rate were positively associated with grain yield under all water regimes while number of kernels per spike and aboveground biomass yield were correlated with grain yield under water stress conditions only. Path analysis revealed that grain-filling rate and grain-filling period had high positive direct effect on grain yield under continuous stress from tillering to crop maturity and well-watered conditions. Aboveground biomass and harvest index had positive direct effect on grain yield under stress treatment from flowering through crop maturity. Similarly, grain filling rate and harvest index had positive direct effect on yield while biomass yield and kernel number per spike had high indirect positive effect on grain yield through grain filling rate and harvest index under water stress from grain filling to crop maturity. Therefore, selection for higher grain filling rate and longer grain filling period under optimal moisture supply to severe stress environment whereas higher biomass yield, harvest index and kernels per spike are expected to improve the yield of durum wheat under moderate water stressed environments.