Evaluation and genome wide association mapping of ethiopian sorghum landraces (Sorghum bicolor (L.) Moench) under moisture stressconditions at miesso, eastern ethiopia

Abstract

Drought is the primary cause of crop yield loss among abiotic factorsaround the world. It is a major problem in Ethiopia, leading to food shortages and is a challenge for small-holder farmers to produce enough sorghum grain when rainfall is low and erratic. Improvement of the crop for drought tolerance related traits requires studying the genetics of the traits.Therefore, the objectives of this study were to assessthe genetic variability among sorghum genotypes for drought tolerance related traits, and identify genomic regions associated with drought related traits. A total of 945 sorghum genotypes collected from different geographic regions were evaluated in an alpha-latticedesign with two replications in 2018/19 main cropping season at Miesso (Eastern Ethiopia). Analysis of variance showed that there was highly significant difference (p<0.01) among the genotypes for all the traits.Genotypic coefficient of variation (GCV) ranged from 4.27% to 52.96%, and phenotypic coefficient of variation ranged from 5.53% to 31.53%. Heritability ranged from 54.75% to 88.9% and genetic advance as a percent of mean (GAM) ranged from 6.78% to 102.87%. Among the traits with high GCV and heritability estimates, panicle length and width, leaf area and number oftillers per plant were in conjunction with higher values of GAM. This indicates that, these traits are controlled by additive genetic factors and less environmental influence. A total of 692 genotypes (73.62%) assigned to either one of the 5 subpopulationswith the admixture coefficient value >60%, while the remaining 248 genotypes (26.38%) were categorized as admixtures. A total of 91 significant (p ≤ 5.21E-5) marker-trait associations were detected for 17 traits, explaining 6.32% to 36.82% of the phenotypic variations and 11 markers, out of 91 were found to be associated with more than one trait. The results of this study showed the existence of genetic variability in the studied genotypes and indicates the presence of opportunity to select a number of promising parental lines with desirable traits related to drought tolerance. The identified genomic regions cloudbe transferred to high yielding but drought susceptible varieties through marker-assisted breeding after a proper validation