GENETIC DIVERSITY AND ASSOCIATION OF SEED YIELD AND RELATED TRAITS IN OKRA [Abelmoschus esculentus (L.) Moench] GENOTYPES

Abstract

Ethiopia is claimed as the likely center of origin for okra [Abelmoschus esculentus (L).Moench], but few studies were conducted to assess the diversity of the crop in the country. Moreover, no attempt has been made to assess the diversity of okra genotypes for seed yield and related traits though the crop is known for the production of quality edible oil. Therefore, this study was conducted with the objectives of assessing genetic variability among okra genotypes for seed yield and related traits, and to determine the association of traits. A total of 24 okra genotypes (14 and 10 from Ethiopia and other countries, respectively) were evaluated for 4 qualitative and 20 quantitative traits, at Dire Dawa in 2017. The field experiment was laid out in randomized complete block design (RCBD) with three replications. The results from analysis of variance revealed the presence of significant differences among genotypes for all quantitative traits. Moreover, the variation of genotypes for seed yield per hectare ranged from 122 to 3206 kg with mean seed yield of 1938.13 kg ha-1. The 14 okra genotypes collected from Ethiopia had mean seed yield advantage of 43.08% over the introduced varieties. In addition, most of the okra genotypes from Ethiopia had higher mean values than introduced varieties for majority of the traits. The largest proportion of okra genotypes had desirable qualitative traits of green pod color, erects fruit position on stem and smooth pod. The phenotypic (PCV) and genotypic (GCV) coefficient of variations varied in the range between 8.35% to 57.70% and 5.44 to 49.20%, respectively. Heritability in broad sense (H2) and genetic advance as percent of mean (GAM) ranged from 20.92 to 94 % and 5.13 to 91.94%., respectively. All the estimated variability components (GCV, PCV, H2 and GAM) were high for all traits except days to first flowering, days to 50% flowering and days to maturity. Majority of the traits had positive phenotypic and genotypic correlations with seed yield per hectare. Moreover, the seed weight per pod followed by weight of dry pod per plant, stem diameter, internode length and plant height had positive and highly significant correlations with seed yield per hectare and had positive genotypic direct effect on the trait. Therefore, these traits could be considered in selection for high seed yield per hectare. The genetic distances of 24 okra genotypes ranged from 1.96 to 11.36 and the genotypes were grouped into seven distinct clusters. Cluster III (41.67%), I (20.83%) and V (16.67%) consisted of the largest proportion of genotypes while Cluster II, IV and VII consisted each of one genotype and Cluster VI consisted of two genotypes. Okra genotypes with high seed yield and high mean values for most of the traits were grouped in Cluster III and IV of all genotypes except the one obtained from Ethiopia. The introduced varieties tend to be grouped in the same clusters with lower genetic distance with others than genotypes obtained from Ethiopia. The results suggested the possibility of developing varieties for high seed yield through selection and/or crossing of distant genotypes collected from Ethiopia.