Abstract:
Groundnut is one of the most important oil crops in Hararghe, Eastern Ethiopia. However, the production of the crop is constrained by several biotic and abiotic factors of which lack of improved varieties is among the major constraints. Therefore, the current study was conducted with the objectives of assessing the extent of genetic variability and characters association and to determine direct and indirect effect of yield related characters and oil content on grain yield. The experiment was conducted at Dire Dawa in 2017/2018 during main rain season. Thirty six groundnut genotype including three released varieties were tested in 6x6 triple lattice designs. Data were collected for 15 traits and subjected to analysis of variance, followed by further genetic analyses. The analysis of variance revealed highly significant variation among genotypes for all the studied characters except number of seed per pod indicated the presence of variation among the groundnut genotypes studied. High phenotypic coefficient of variation (PCV) and medium genotypic coefficient of variation (GCV) values estimated for grain yield hectare-1 and secondary branches plant-1 . Moderate value of PCV and GCV were observed for primary branches plant-1 , dry pod yield hectare-1 , mature pod plant -1 , total pod plant-1 , plant height, pod length, and shelling percentage. These indicated the existence of wider genetic variation in the tested genotypes and implied that there is a good opportunity for the improvement of these traits in the tested genotypes. Hence, those character can be relied upon and simple selection for improvement. High heritability coupled with high genetic advance as per cent of means were estimated for grain yield hectare-1 , secondary branches plant-1 , mature pod plant-1 , plant height and shelling percentage; indicating the role of additive gene action in expression of these traits and revealed better scope for improvement of these traits through selection. Correlation coefficient analysis revealed that Grain yield hectare-1 had positive and highly significant association with days to 50% flowering, days to 90% maturity, primary branches plant-1 , total pods plant-1 , mature pods plant-1 , shelling% percentage, hundred seed weight, oil content and dry pod yield hectare1 at both phenotypic and genotypic levels. The maximum positive direct effect on grain yield hectare-1 both at phenotypic and genotypic levels was exerted by dry pod yield hectare-1 , primary branches plant-1 , mature pod plant-1 , hundred seed weigh, whereas maximum negative direct effect on grain yield was exerted by number of total pod per plant and pod length both at phenotypic and genotypic levels. Total pod per plant and pod length had highest positive indirect effect on grain yield hectare-1 via dry pod yield hectare-1 , mature pod plant-1 , primary branches plant-1 and hundred seed weight. Principal component analysis extracts four principal components, which cumulatively explained 76.84% of the total variations. The variances explained by PC1, PC2, PC3, PC4 were 51.56%, 10%, 8%, 7%, respectively. Cluster analysis grouped genotypes in to five clusters. The maximum inter Cluster distance observed between cluster I and V whereas the minimum was between cluster III and IV. The results indicate that selection based on dry pod yield hectare-1 , mature pod plant -1 and primary branch plant-1 would be important traits in future breeding program of groundnut. In addition, crossing between genotypes selected from cluster I and V would be effective to improve the yield performance of these groundnut genotypes.