GENETIC VARIABILITY AND ASSOCIATION OF YIELD AND YIELD RELATED TRAITS IN BREAD WHEAT (Triticum aestivum L.) GENOTYPES IN SOUTHERN ETHIOPIA

Abstract

Bread wheat productivity in Ethiopia is low as compared to the world average productivity due to limited availability of improved high yielding varieties with resistance to various diseases and adaptive to abiotic stress conditions.Assessment of genetic variability is one of the most important activities in plant breeding for improving crops and enhancing production.Therefore, 36 bread wheat genotypes were studied for genetic variability and association of traits with the objective of investigating the extent of genetic variability among bead wheat genotypes. The experiment was laid out in (6x6) simple lattice design with two replications in Doyogena and Kokate research sites of Southern Ethiopia in 2022/23 main cropping session. Traits describing growth, phenology, yield and yield-related characters were collected and subjected to analysis of variance. There were highly significant differences observed among the genotypes for all traits studied across locations. The variation observed among genotypes for grain yield ranged from 2188.9- 6793.8 kg/ha. The top five genotypes have yield advantage of 13- 23% compared with the best performing standard check Bondena. The Phenotypic coefficient of variation (PCV) and genotypic coefficient of variation (GCV)ranged from (4.93% and 4.87%) for days to maturity to (25.62% and 25.20%) for productive tillers per plant, respectively. High PCV and GCV were observed for productive tillers per plant, biomass yield, and grain yield, suggesting selection could be effective based on these traits. High estimates of heritability (H2 ) in a broad sense were observed for all traits, which ranged from (66.14%) for harvest index to (99.94%) for grain felling period. Expected genetic advance expressed as a percent of means (GAM) ranged from 9.88% for harvest index to 51.14% for productive tillers per plant. High H 2 coupled with high GAM were recorded for days to heading, productive tillers per plant, number of kernels per spike, thousand kernel weight, grain yield, and biomass yield. Both at genotypic and phenotypic levels, grain yield exhibited a positive and highly significant correlation with spike length, productive tillers per plant, number of kernels per spike, number of spikelets per spike, thousand kernel weight, and biomass yield. A higher positive direct effect on grain yield was exerted by biomass yield, followed by days to heading at genotypic level, whereas days to maturity followed by biomass yield at phenotypic level. This indicates that these traits could be the main contributors to grain yield. Principal component analysis (PCA) revealed that, the first four components accounted for 80.75% of the total variation with an Eigen value greater than one. Cluster analysis grouped the thirty-six genotypes into four distinct clusters. In conclusion, the findings of this study revealed the presence of sufficient genetic variability in the bread wheat genotypes studied. Attention should be given to traits with moderate to high heritability and expected genetic advance expressed as a percent of means that exert a positive direct effect on the grain yield to carryout selection