GENETIC VARIABILITY AND ASSOCIATION OF YIELD AND YIELD RELATED TRAITS IN BREAD WHEAT (Triticum aestivum L.) GENOTYPES AT GEDO, WESTERN OROMOIA, ETHIOPIA

Abstract

West Shewa is one of the major wheat production zones of Oromia Regional State in Ethiopia. Developing varieties in the area is one of the measures to increase the production and productivity of the crop. This research was conducted to assess the genetic variability in bread wheat genotypes for morpho-agronomic traits, grain quality and disease resistance, and determine the association among traits. Sixty-four genotypes including two check varieties were evaluated in an 8 x 8 lattice design at Gedo in 2023. The genotypes showed significant differences for most of the morpho-agronomic traits, grain moisture content, gluten content (%), protein content (%), Zeleny index (ml) and percentage of stem rust severity. The average grain yield of genotypes ranged from 2.36 to 4.67 t ha-1 and 13 genotypes had significantly higher grain yield in the range between 8.8 and 24.5% than the better-yielding Laku variety yield (3.7 t ha-1). The genotypes grain gluten, protein content and Zeleny index ranged from 6.5 to 23.5%, 8.7 to 12.7% and 3.9 to 41.7(ml), respectively. The final stem rust severity scores for bread wheat genotypes recorded from 5.5 to 20% and 39 genotypes including the two check varieties were found to possess high-level adult plant resistance. The estimates of phenotypic (PCV %) and genotypic coefficient of variation (GCV %) for 16 traits ranged from 0.8 to 58.66% and 0.6 to 41.3%, respectively. The grain yield had positive and significant genotypic and phenotypic correlation coefficients with days to maturity, plant height, harvest Index, biomass yield and percentage of stem rust severity. In addition, grain yield had positive and significant genotypic and phenotypic correlation coefficients with thousand kernels weight and grain filling period, respectively. Moreover, thousand kernel weight, biomass yield and harvest Index had a high direct positive effect on grain yield indicating these suggested for indirect selection of genotypes for yield. The first six principal components (PCs) accounted for 76.39% of the total variability among the genotypes. Days to heading, grain filling period, days to maturity, grain gluten content, grain protein content, grain and biomass yields, harvest index and spikelet per spike had a larger contribution to total variability in the six PCs suggesting the importance of considering these traits in the evaluating genotypes. The Euclidean distance of all possible pairs of genotypes ranged from 2.02 to 10.6. The 64 bread wheat genotypes were grouped into seven distinct clusters, Cluster I, III and II consisted of 27 (42.19%), 31 (48.44%) and 2(3.13%) genotypes, respectively, while the four Clusters, IV, V VI and VII were solitary. The study displayed that variation exists among bread wheat genotypes; however, the experiment was evaluated at one location and one season of cropping; thus, further confirmation is needed in additional seasons, and multi-locations will be required to develop varieties for the western part of Ethiopia and similar agro-ecologies.