GENETIC VARIATION AND ASSOCIATION OF YIELD AND YIELD RELATED TRAITS IN BREAD WHEAT (Triticum aestivum L.) GENOTYPES UNDER IRRIGATION CONDITION IN SOUTH OMO, SOUTHEREN ETHIOPIA

Thirty six bread wheat genotypes were tested to assess the genetic variability and genetic diversity among genotypes using triple lattice design at Bena-Tsemay district Weyito Nasa Agricultural Farm in 2020 under irrigation condition. The analysis of variance revealed highly significant variation among the genotypes for days to heading, grain filling period, days to maturity, plant height, spike length, number of spikes, number of kernels, 1000 seed weight, and grain yield. Wide ranges of the mean values were observed for most of the characters, indicating the existence of variations among the tested genotypes. Moderate PCV and GCV were recorded for days to maturity, grain yield, and harvest index; while high heritability values were observed for plant height and days to heading. Low PCV and GCV were recorded for 1000 kernel weight, number of grains spike-1 , grain filling period, and spike length. Among the characters studied, grain yield showed high genetic gain whereas days to maturity and grain filling period had moderate values of genetic advance as percent of mean (GAM). Characters like grain filling and plant height were significant and positively correlated at phenotypic and genotypic levels with days to maturity and number of kernel per spike, days to heading and harvest index. The Phenotypic path coefficient analysis showed that biomass followed by seeds per spike and days to maturity exerted highest positive direct effect on grain yield. The maximum positive genotypic direct effect on grain yield was exerted by days to maturity (1.358) followed by biomass yield (0.855), fertile tiller per plant (0.763), harvest index (0.383) ,number of kernel (0.305) and plant height (0.047). The D2 analysis grouped the 36 genotypes into six clusters. The maximum inter cluster distance was observed between cluster V and VI (D2=777.99), followed by that between clusters III and V (D2=525.49) and I and III (D2=310.81), which showed that the genotypes included in these clusters are genetically more divergent from each other than those in any other clusters. Crosses between genotypes selected from cluster V with cluster VI, cluster III with cluster V and cluster I with cluster III are expected to produce relatively better genetic recombination and segregation in their progenies. Principal components (PC1 to PC6) having Eigen value greater than one (significant), accounted 75.6% of the total variation. The first three principal components, i.e., PC1, PC2 and PC3, with values of 22.0, 35.7, and 47.9, respectively, contributed more to the total variation. Generally, the results of this study showed the presence of variations among the studied genotypes for agro-morphology traits with wide range of genetic distances that could allow selection and/or hybridization of genotypes .