GENETIC VARIABILITY AND ASSOCIATION AMONG SEED YIELD AND YIELD RELATED TRAITS IN BREAD WHEAT (Triticum aestivum L.) GENOTYPES AT OFLA DISTRICT, NORTHERN ETHIOPIA

In plant breeding programs knowledge of nature and magnitude of variation existing in available plant breeding materials, interrelationships between quantitatively inherited plant traits and their direct and indirect effects on grain yield is of great importance. To generate such objectives, a field experiment was conducted in 2014 cropping season at Ofla district, Northern Ethiopia. 26 bread wheat genotypes were used in Randomized Complete Block Design with three replications for the study.12quantitative traits were subjected to analysis of variance and genetic analyses. There were significant differences among genotypes for 10 quantitative traits including grain yield which ranged from 2.96 (Digalu) to 6.35 t ha-1(ETBW7888) with the mean value of 4.25 t ha-1. Genotypic coefficient of variation (GCV) was ranged from 5.68 for Days to maturity (DM) to 17.56% for biomass yield (BY). Phenotypic coefficient of variation (PCV) ranged between 6.23% (DM) to 32.29% (BY). Heritability in broad sense and genetic advance as percent of mean was ranged from 4.57% for Number of tillers per plant (NT) to 96.86% for thousand seed weight (TSW) and 3.04% (NT) to 19.74% (BY) respectively. High heritability estimates and moderate genetic advance as percent of mean was computed for days to heading, DM and TSW. GCV and PCV values had low magnitude of differences. Hence, the traits are highly heritable; the influence of environment was less. Selection based on these traits would improve the characters. Grain yield (GY) was positively correlated with NT, number of kernels per spike (NKS) and BY. BY had strong and positive direct effect on GY, but, NT and NKS had low direct effect. Positive and strong genotypic and phenotypic indirect effect on GY via BY suggested that selection on BY would lead to increment of GY directly and selection on NT and NKS indirectly via biomass yield. The squared distance (D2) statistics grouped the 26 bread wheat genotypes into three clusters. Cluster I, II and III comprised 6, 14 and 6 genotypes respectively. The average inter-cluster distances were highly significant (P