Morphological characterization and divergence analysis of okra (Abelmoschus esculentus (L.) Moench) collections at gambella, south western Ethiopia

Abstract

Okra(Abelmoschus esculentus (L.) Moench) is an economically important vegetable crop grown in tropical and sub-tropical parts of the world which belongs to family Malvaceae. It is apparently originated in Ethiopia. The objectives of the study were to characterize accessions based on qualitative and quantitative morphological traits and determine the range of diversity among the accessions with the ultimate goal of providing a basis for varietal improvement and conservation. Twenty five okra accessions were planted in 2011/ 2012 at Gambella in randomized complete block design with three replications. Data on eight qualitative and 20 quantitative traits were collected and subjected to various statistical analyses. Cluster analysis based on qualitative characters indicated the formation of four clusters and existence of wide variability based on their vegetative, shape, pigmentation, growth and fruit characteristics. The analysis of variance showed significant differences (p<0.01) among the accessions for all characters measured. Estimate of phenotypic and genotypic coefficients of variation also showed the presence of variability among the accessions for the majority of the character. Relatively high phenotypic (137.25, 118.10, and 92.08%) and genotypic coefficients of variation (106.58, 89.79 and 88.89%) were observed for days to maturity, number of primary branch and fruit length respectively. High heritability (96.76% and 96.50%) coupled with high genetic advance as percent of mean (106.32% and 97.25%) were recorded for internodes length and plant height respectively. Correlation study between various quantitative characters highlighted significant association among characters fruit yield was positive and highly significant genotypic correlation with fruit length (r= 0.74), average fruit weight (r= 0.62), fruit diameter (r= 0.61), seed per pod (r= 0.56), hundred seed weight (r= 0.68), internodes number (r=0.89, plant height (r= 0.58), and number of pod per plant (r=0.66). Path coefficient analysis at genotypic level revealed that internodes number had highly positive direct effect on fruit yield (p = 6.90) followed by average fruit weight (p = 6.89) which had positively genotypic correlation with yield. Cluster and distance analysis of quantitative characters based on multivariate analysis pointed out the existence of five divergent groups. The maximum distance was observed between cluster II and I (2846) while the minimum was between I and III (213.64). Principal component analysis indicated that six principal components explained about 83% of the total variation. Differentiation of germplasm into different cluster was because of cumulative effect of number of characters. Accession like GM7, GM9 and GH13 from Gambella collection AS4 and AS11 from Assosa collection are recommended if they promoted for the next breeding work as they are high yielder accessions compared to the others. The present study indicated a considerable amount of variability for the majority of the qualitative and quantitative characters in okra for exploitation. However, it is recommended that the experiment should be repeated at more location and years with more collections to confirm the obtained results.