GENETIC VARIABILITY AND ASSOCIATIONS AMONG YIELD, YIELD COMPONENTS AND QUALITY TRAITS IN ADVANCED BREAD WHEAT (Triticum aestivum L.) GENOTYPES AT SINANA, SOUTH EASTERN ETHIOPIA

Abstract

Information on the extent of genetic variation and associations among characters is important to design breeding strategies and to develop varieties for the targeted area of production. Therefore, this research was conducted at Sinana Agriculture Research Centre testing site and at Robe on farm, south eastern Ethiopia, with the objectives of evaluating advanced bread wheat genotypes for yield, yield related and quality traits, to assess associations among yield, yield components and quality traits, and to determine the direct and indirect effects of yield related traits on yield. The experiment was conducted in 2016 cropping season using 21 promising lines and 4 released varieties in triple lattice design. Data were collected for 9 agronomic and 13 grain quality characters. Pooled analysis of data showed that there was significant (P<0.01) differences among genotypes for days to maturity, harvest index, hectolitre weight, wet gluten content, dry gluten content, gluten index, average kernel thickness, SDS sedimentation test, protein content and moisture content. For genotype x environment interaction, for wet gluten content, dry gluten content, gluten index, average kernel thickness, SDS sedimentation test, protein content and moisture content revealed significant (P<0.01) differences among genotypes. Analysis of variance revealed the presence of highly significant (P ≤ 0.01) variation among genotypes except for day to maturity, number of tillers, harvest index, grain hardness and hectoliter weight at Sinana, and number of tillers and harvest index at Robe. The highest and lowest grain yields of 6.4 and 4.6 t ha-1 were obtained from ETBW7435 and ETBW7524, respectively, with the mean value of 5.5 t ha-1at Sinana and 3.6 t ha-1 at Robe. In pooled analysis, genotypic coefficient variation (GCV) and (PCV) was relatively higher for SDS sedimentation followed by wet gluten content. Vitreousness (1.7%) and days to heading (2.2%) while number of kernel per spike (13.7%) and grain hardness (13.6%) had lowest and highest GCV at Sinana and Robe, respectively, vitreousness (2.7%) at Sinana and days to heading (2.2%) at Robe exhibit lowest PCV, while number of kernel per spike and grain hardness had highest value of 13.7 and 17.6% at Sinana and Robe respectively. In all studied traits, the phenotypic coefficient of variation values were higher than genotypic coefficient of variation values at both locations, indicating the higher influence of environmental factors than genetic factors for the phenotypic expression. In pooled analysis heritability in broad sense and genetic advance as percent of mean (GAM) ranged from 38.6% (dry gluten content) to 97% (SDS sedimentation test) and 1.7% (days to maturity) to 34.5% (SDS sedimentation). High heritability coupled with genetic advance was observed for SDS sedimentation in combined analysis. This implies the potential of improving wheat for end product use quality through direct selection. At Sinana, grain yield had high genotypic correlation with days to heading, spike length and spikelet per spike. Days to heading and spikelets per spike had strong and positive direct effect on grain yield, but, spike length had negative direct effect. At Robe, harvest index and days to heading showed highest positive direct effect on grain yield but exerted negative indirect effects through each other on grain yield. Generally, it has been observed the presence of variability among the genotypes studied and the possibility of increasing grain yield and quality traits to improve yield in the study area. However, this study was conducted for one season and at two locations which needs to be tested subsequent breeding trials at different season and locations to develop high yielding with better grain quality varieties.