Tesfaye, Kassahun (PhD)Tadesse, Endeshaw2022-02-082023-11-082022-02-082023-11-082021-12-31http://etd.aau.edu.et/handle/123456789/29958The genetic variation in a breeding program is created by crossing genetically divergent parents. The resulting genetic variation between and within crosses is the determining factor for the offspring’s performance, which is defined as the level of compliance of the offspring with preset breeding goals. Estimation of breeding parameters plays a key role in crop improvement. The aim of this study was to (i) estimate and compare mid-parent value and the cross mean (ii) estimate and compare the variance between means of crosses (σ²c) and segregation variance of recombinant inbred line within crosses (σ²g) (iii) estimate correlation among the traits measured and their heritability (iv) estimate and compare Rogers Distances (RD) of parental lines and their correlation to the segregation variance within crosses, and (v) estimate usefulness of crosses. 900, F4:5 recombinant inbred lines randomly derived from 30 crosses were evaluated at two locations in modified split plot p-rep design whereas the parental where genotyped using SNP-KASP markers. The variance component analysis revealed significant (P <0.05) genetic variation among parents, crosses and RIL for almost all traits. Based on generation mean analysis, the means of recombinant inbred line did not deviate significantly from the means of parental lines. The range of σ²g for the individual crosses was very high for days to heading, days to maturity, plant height, thousand kernel weight and grain protein concentration and for these traits the respective standard deviation were high. Heritability for parents ranged from 49.50 % (malt extract) - 93.60 % (plant height), heritability for crosses ranged from 29.52 % (grain protein concentration) - 87.0% (days to maturity), whereas heritability for RIL was lowest with 27.40% (beta-glucan) - 73.60% for thousand kernel weight. Significant (P<0.01) genotypic correlations with high impact for practical breeding were found between malting traits. Significant (P<0.01) regression of cross mean on mid-parent value were obtained for all traits demonstrating that cross means can accurately be predicted from mid parent values and selection among crosses at an early stage of line development is highly effective. Further, based on the usefulness criteria, 16 outperforming crosses were identified that surpass Planet as the actual leading malt variety. Diversity analysis revealed an average RD between lines was 0.46 with a range of 0.32- 0.64 and homogeneity within the 17 parental lines varied from 71-100%. The dendrogram grouped the lines into three clusters. Importantly, the high malting European lines were grouped together with some of the ICARDA and Ethiopian lines Correlations of RD to σ²g ranged from -0.19 to 0.34 and were not significantly deviating from zero for all traits except DH, hence, RD proved to be not predictive for σ²g. In this study the two variances, σ²c and σ²g, proved to be significantly deviating from zero for almost all traits; hence breeder can exploit both of them for selection. Generally, differences between generation means (Parental lines vs. RIL) were small across all crosses. But when grouping into crosses with and without Planet as a parental line, deviation between parent and RIL were larger possibly due to epistastic effects. Hence breeder should estimate breeding values rather than genetic values of parental lines. The use of mid-parent value and usefulness for cross selection were found to be promising. The national barley breeding program should exploit this result by starting with a large number of initial crosses and reducing them to the most promising crosses. Some heterogeneity was observed within the lines. When originating from technical mixture this should be considered as a wake-up call for the breeder to closely follow maintenance breeding. RD based on KASP markers was not predictive for σ²g; hence further research will be required by improving accuracy of σ²g estimate and linkage disequilibrium between markers and quantitative trait loci (QTL). Over all, the large diversity revealed among lines indicates the potential that the genotypes have to improve the productivity and quality of the crop and the uses of molecular markers can benefit the breeding program in order to have an effective breeding program by selecting diverse parental genotypes with complementary gene action.enParentCrossRilHeritabilityUsefulnessGenetic DiversityThesis