GENOTYPIC VARIATION FOR YIELD AND QUALITY CHARACTERS IN BREAD WHEAT (Triticum aestivum L) GENOTYPES IN CENTRAL TIGRAY, NORTHERN ETHIOPIA

xvi GENOTYPIC VARIATION FOR YIELD AND QUALITY CHARACTERS IN BREAD WHEAT GENOTYPES IN CENTRAL TIGRAY, NORTHERN ETHIOPIA ABSTRACT Development of wheat varieties for high yield with desirable grain quality for different agro ecologies of the country is important. Estimation of variability is critical for variety development. This study was conducted at Axum Agricultural research center in 2016/17 main season to assess the extent of genetic variability of wheat genotypes for yield, yield related and grain quality characters as well as to determine association among characters. The experiment was laid out using 7 x 7 triple lattice design. Data were collected for 17 agronomic and grain quality characters, and subjected to analysis of variance which, revealed significant differences among the genotypes for all the characters. Grain yield ranged from 2.37 to 5.44 t ha-1 with a mean of 3.95 t ha-1, while grain protein content ranged from 11.93 to 15.43%, with a mean of 13.79%. Moreover, four new entries (ETBW8486, ETBW8475, ETBW8480 and ETBW9016) produced yield ranging from 4.52 to 5.44 t ha-1 and protein content of 13.1 to 14.67% which is higher than that of the best performing check variety (King bird). Most of these genotypes were also early maturing (97-105 days) than the released varieties. The genotypic coefficient of variation (GCV) ranged from 1.63 (for starch content) to13.30% (for grain yield), while phenotypic coefficient of variation (PCV) varied from 1.63 (starch content) to 21.88% (for number of effective tillers). The broad sense heritability (H2) ranged from 15.89 (for number of tillers) to 97.1% (DH), while genetic advance as percent of mean (GAM) ranged from 2.01(for starch content) to19.63% (for days to heading). The GCV and PCV differences were low in magnitude for days to heading and days to maturity and H2 values for these traits were coupled with moderate to high GAM, suggesting that selection based on phenotype of genotypes could be effective to improve these characters. Grain yield was positively and significantly correlated with biological yield (BY) (0.72), harvest index (HI) (0.65), plant height (PH), thousand kernel weight (TKW) (0.31), hectoliter weight (HLW) (0.37) and starch content (SC)(0.32) of which BY and HI had the highest positive direct effect on grain yield at the genotypic levels. Selection for higher mean values of BY and HI could be considered simultaneously for selection of higher yield, while selection for PH, TKW and HLW could be used as indirect selection of genotypes for grain yield. The genetic distances measured by D2 and Ward's clustering method grouped the 49 genotypes in to five distinct clusters of which Cluster II and Cluster I comprised of 15 (30.61%) and 13 (26.53%) genotypes (superior for BY and GY), respectively. Clusters III and IV consisted of eight genotypes each and Cluster V contained five genotypes which are superior for Grain quality traits and early maturity. The maximum distances were observed between Cluster V and IV (123.48) thus, greater heterosis in the F1. The first five principal components explained 80.12% of the total variation. The study indicated the presence of wide variation among the 49 wheat genotypes, which could be exploited to develop high yielding varieties with desirable grain quality and early maturing genotypes, where terminal moisture stress is the major constraint in Axum. Hence, ETBW8486, ETBW8480 and ETBW9016 can be candidate genotypes after results are confirmed across locations and over years. Keywords: