Investigation of genetic variability and characters association in F6 generation of okra

Introduction

Okra [Abelmoschus esculentus (L.) Moench], popularly known as lady's finger, bhindi or gumbo, is an economically important vegetable crop belonging to the family Malvaceae. The crop is widely appreciated for its nutritional value and its ability to thrive under diverse tropical and subtropical growing conditions (Temam et al., 2021) [19] . It has a somatic chromosome number of 2n = 130 and is generally believed to have originated in Africa. Over the years, its adaptability and versatility have contributed to its widespread cultivation across different parts of the world. India holds a prominent position in global okra cultivation and production, contributing nearly 72 per cent of the total world output. In the country, okra is cultivated over an area of approximately 554 thousand hectares, producing about 7,289 thousand tonnes of tender fruits annually, with an average productivity of 13.15 tonnes per hectare. The crop is predominantly cross-pollinated, and insects serve as the major agents responsible for pollen transfer among flowers. Natural outcrossing in okra is not constant and may vary from about 4 to 19 per cent depending upon environmental conditions and the activity of pollinating insects. Such a degree of cross-pollination contributes to the maintenance and generation of genetic variability, thereby offering substantial opportunities for selection and genetic improvement of important yield and yield-related traits.

Materials and methods

The present study entitled "Investigation of Genetic Variability and Characters Association in F6 Generation of Okra" was conducted at the Instructional Farm, Department of Vegetable Science, Dr. Panjabrao Deshmukh Krishi Vidyapeeth, Akola, during the kharif

Results and Discussion

The experimental data on quantitative traits were subjected to analysis of variance (ANOVA) as described by Panse and Sukhatme (1967) [14] to test the significance of differences among genotypes. Genotypic and phenotypic coefficients of variation (GCV and PCV), proposed by Burton and Devane (1953) [2] , were used to assess genetic and total phenotypic variability. Heritability, as suggested by Lush (1949), indicates the proportion of phenotypic variation due to genetic effects, while genetic advance (GA) and genetic advance as per cent of mean (GAM), as described by Johnson et al. (1955) [7] , indicate the expected progress through selection. Genotypic, phenotypic and environmental correlations were estimated following Johnson et al. (1955) [7] to determine the strength and direction of relationships among traits. Path coefficient analysis, as proposed by Dewey and Lu (1959), was used to partition correlations into direct and indirect effects on fruit yield per plant. Together, these analyses helped identify genetically important and yield-contributing traits that could serve as effective selection criteria for improving fruit yield in okra.

Analysis of variance

The analysis of variance revealed that the treatment mean squares were highly significant for all the characters studied, indicating the presence of significant differences among the evaluated okra genotypes. The highest treatment variation was recorded for plant height followed by fruit yield per hectare and fruit yield per plant showing considerable variability for growth and yield attributes. Overall, the significant treatment effects for all characters demonstrate adequate genetic variability among the studied genotypes, which is essential for effective selection and breeding of superior-yielding okra genotypes. [18] . The lowest variability was recorded for days to 50 per cent flowering (GCV 9.10%, PCV 10.73%) followed by fruit weight (9.20%, 11.76%) and days to first flowering (10.70%, 11.92%). The narrow differences between GCV and PCV indicate that environmental effects were comparatively limited, while the genetic component contributed considerably to trait expression. Similar findings have been reported in okra by Khajuria et al. (2016) [8] .

Heritability and genetic advance mean:

The estimates of heritability and genetic advance indicated substantial genetic control for most of the traits studied.

Fruit diameter recorded the highest heritability (95.47%) [12] , Gohil et al. (2024) [5] . [6] , Mishra et al. (2015) [11] and Syfullah et al. (2018) [18] . On the other hand, internodal length (r = 0.014), fruit diameter (r = 0.044), days to first flowering (r = 0.063) and days to 50 per cent flowering (r = 0.152) showed positive but non-significant genotypic associations with fruit yield per plant. Similar finding reported by Sharma et.al. (2022) [17] .

Overall, number of fruits per plant emerged as the most important trait associated with fruit yield, indicating its usefulness as a selection criterion for yield improvement in okra. The findings are also supported by Nwangburuka et al.

(2012) [13] and Syfullah et al. (2018) [18] , who reported significant associations among yield and its contributing traits.

The phenotypic correlation

Analysis revealed that fruit yield per plant showed the highest positive and highly significant association with number of fruits per plant (r = 0.762**), followed by number of branches per plant (r = 0.464**) and fruit weight (r = 0.220**). Plant height (r = 0.122*) and fruit length (r = 0.184) also showed positive significant associations with yield, indicating their importance in improving fruit productivity. Similar positive associations of fruit yield with number of fruits, fruit weight, fruit length and other yield components were reported by Balakrishnan and Sreenivasan (2010) [1] and Walling et al. (2020) [20] . On the other hand, internodal length (r = 0.006), fruit diameter (r = 0.031), days to first flowering (r = 0.075) and days to 50 per cent flowering (r = 0.176) showed positive but non-significant genotypic associations with fruit yield per plant. Similar finding reported by Sharma et.al. (2022) [17] . Overall, number of fruits per plant emerged as the most important phenotypic correlate of fruit yield, suggesting its usefulness as a selection criterion for yield improvement. The present findings are also supported by Jagan et al.

(2013) [6] , who observed highly significant positive phenotypic associations of fruit yield with number of branches and number of fruits per plant.

Path analysis

The path coefficient analysis revealed that number of fruits per plant exhibited the highest positive direct effect on fruit yield per plant (0.9678), followed by fruit weight (0.4168), days to first flowering (0.1304), fruit diameter (0.0573) and plant height (0.0029). The strong direct contribution of number of fruits per plant, together with its high positive genotypic correlation with yield (r = 0.9127), indicates that it is the most important trait for improving yield through direct selection. Similar importance of number of fruits per plant and fruit weight in determining yield was reported by Yadav et al. (2010) [21] , Ramanjinappa et al. (2011) and Sharma and Prasad (2015) [16] . In contrast, days to 50 per cent flowering showed the highest negative direct effect (-0.1206), followed by internodal length (-0.0694), fruit length (-0.0886) and number of branches per plant (-0.0088). The negative direct effect of internodal length suggests that excessive vegetative elongation may not favour yield formation. Similarly, the negative direct effect of days to 50 per cent flowering indicates that delayed flowering may reduce yield potential. Interestingly, number of branches per plant showed a positive genotypic correlation with yield (r = 0.4889) despite its negative direct effect, mainly because of its strong positive indirect contribution through number of fruits per plant (0.3915) and fruit weight (0.1052). Similar negative direct effects of branches and flowering-related traits have been reported by Sharma and Prasad (2015) [16] .

The number of fruits per plant recorded the highest positive direct effect (0.9678) and also showed the strongest positive genotypic correlation with fruit yield (0.9127**), clearly establishing it as the most important selection criterion for yield improvement. The residual effect was low (0.087), indicating that most of the variation in fruit yield was explained by the characters included in the path analysis. Similar findings emphasizing number of fruits per plant and fruit weight as important selection criteria have been reported by Ramanjinappa et al. (2011) [15] , and Sharma and Prasad (2015) [16] .

Conclusion

The present study revealed substantial genetic variability among the evaluated okra genotypes, providing good scope for effective selection and further genetic improvement. AKOH-3, AKO-11, AKOR-25 and AKO-10 were identified as promising genotypes for fruit yield. High heritability coupled with high genetic advance for several yield and yield-contributing traits indicated considerable scope for selection. Correlation analysis showed a strong positive association of number of fruits per plant with fruit yield, while path analysis revealed its highest positive direct effect (0.9678). Therefore, number of fruits per plant may be considered an important selection criterion for improving fruit yield in okra. The identified superior genotypes and important yield-associated traits can be effectively utilized in future selection and hybridization programmes.

Acknowledgement

AcknowledgementI am thankful to the Department of Vegetable Science, Dr. Panjabrao Deshmukh Krishi Vidyapeeth, Akola, and Maharashtra for providing the necessary facilities to carry out the experimental work.

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