Genetic variability and heritability studies in okra

Introduction

Okra [Abelmoschus esculentus (L.) Moench], a member of the family Malvaceae with a chromosome number of 2n = 130, is a major vegetable crop of global importance. It is widely cultivated in tropical, subtropical, and warm regions, including India, Africa, Turkey, and neighboring countries. In India, it is valued as one of the leading vegetable crops, primarily grown for its tender green fruits during summer and monsoon seasons. Genetic variability plays a central role in okra breeding programs by supporting yield improvement, disease resistance, and nutritional quality. It aids in developing varieties adapted to diverse environments and market demands, while also providing resilience against pests and diseases for sustainable production. Intensive breeding efforts utilizing this variability have already resulted in several improved cultivars. However, genetic drift and rising susceptibility to pests and pathogens often reduce the long-term effectiveness of such varieties, making continuous development of new lines essential. Assessing the extent of variability is therefore crucial, as it underpins effective selection in breeding. The success of any crop improvement program largely depends on the availability of useful variability and the heritability of desirable traits. Estimates of the genotypic coefficient of variation (GCV), combined with heritability, are reliable indicators of the genetic gain expected from selection (Burton, 1952) [4] . With this perspective, the present study was conducted to evaluate genetic variability and heritability in okra for supporting future breeding strategies.

Materials and Methods

The present study, entitled "Genetic variability and heritability studies in okra", was carried out during the summer of 2024-2025 at the Instructional Farm, Department of Vegetable Science, Dr. Panjabrao Deshmukh Krishi Vidyapeeth, Akola. The experimental material included 21 okra genotypes sourced from various institutes and evaluated under a Randomized Block Design (RBD) with two replications. The main aim was to assess the magnitude of genetic variability, heritability, and genetic advance for yield and its component traits.

Five randomly chosen plants per genotype were tagged to record data on: plant height at 90 DAS, days to 50% flowering, number of internodes on the main stem, number of branches per plant at 90 DAS, days to first picking, fruit length (cm), fruit width (mm), fruit weight (g), number of fruits per plant, fruit yield per plant (g), chlorophyll content of leaves (mg/g), and fruit moisture content (%). Meteorological information was collected from the Meteorological Observatory, Department of Agronomy, Dr. PDKV, Akola. Standard practices for manuring, fertilization, plant protection, irrigation, and other cultural operations were followed. Treatments (genotypes) were randomly allotted within blocks. The phenotypic and genotypic coefficients of variation (PCV and GCV) were calculated following Burton (1952) [4] . Broad-sense heritability, genetic advance (GA), and genetic advance as a percentage of mean (GAM) were estimated as per Robinson et al. (1949) [15] .

Results and Discussion

Variability across okra genotypes was assessed using mean values, GCV, and GAM. Substantial variation in mean performance was noted for all characters studied (Table 1), including plant height at 90 DAS, days to 50% flowering, number of internodes, number of branches per plant, days to first picking, fruit length, fruit width, fruit weight, number of fruits per plant, fruit yield per plant, chlorophyll content, and fruit moisture content. The highly significant differences observed confirm the existence of a broad genetic base, highlighting good prospects for crop improvement through selection. Wide variability was particularly evident in yield-related traits. Fruit yield per plant ranged from 80.90 to 236.60 g with an average of 155.99 g, followed by plant height at 90 DAS (66.35-84.24 cm; mean 74.63 cm), number of internodes (8.60-11.45; mean 10.44), number of fruits per plant (8.10-20.50; mean 15.30), fruit width (10.89-22.67 mm; mean 14.79 mm), days to 50% flowering (41.50-52.50 days; mean 47.19 days), and days to first picking (47.50-58.50 days; mean 53.07 days). Such variability reflects the scope for selection and yield enhancement. Similar results were earlier reported by Burse (2012) [3] , Priyanka et al. (2018) [10] , Patil (2020) [9] , and Shravanthi et al. (2021) [16] . In all traits studied, PCV values exceeded GCV values, indicating environmental influence on trait expression. However, the relatively narrow gaps between PCV and GCV suggested that most of the observed variability was genetic rather than environmental. These findings agree with Koundinya et al. (2013) [6] and Reddy et al. (2012) [14] . The PCV ranged from 4.062% to 35.726%, with the highest recorded for chlorophyll content (35.726%), followed by fruit width (29.688%), number of branches per plant (24.782%), fruit yield per plant (24.707%), and number of fruits per plant (20.096%). These results are in line with Thulasiam et al. (2017) for number of branches per plant and Patil et al. (2020) [9] for fruit yield per plant. Low phenotypic coefficients of variation (PCV) were observed for traits such as fruit moisture content (4.062%), plant height (6.005%), days to 50% flowering (6.569%), days to first picking (6.335%), and number of internodes on the main stem (6.334%). Comparable results for PCV in plant height and days to 50% flowering were earlier reported by Patil (2020) [9] . Traits like fruit length (13.111%) and fruit weight (10.502%) exhibited moderate PCV values, which closely align with the findings of Kumari et al. (2019) [7] , and for fruit length, with the observations of Thulasiram et al. (2017) [17] . The genotypic coefficient of variation (GCV) ranged between 3.347% and 32.090%. Maximum GCV values were recorded for leaf chlorophyll content (32.090%), fruit width (25.999%), fruit yield per plant (24.382%), and number of branches per plant (23.987%). These results are consistent with the findings of Patil (2020) [9] for fruit yield per plant and Thulasiram et al. (2017) [17] for number of branches per plant. Conversely, traits such as fruit moisture content (3.347%), plant height (3.892%), days to first picking (5.464%), days to 50% flowering (5.905%), and number of internodes on the main stem (4.069%) exhibited low GCV values. Similar observations were previously reported by Thulasiram et al. (2017) [17] for days to first picking and by Reddy et al. (2022) [13] for days to 50% flowering. Moderate GCV values were noted for number of fruits per plant (19.909%), fruit length (12.691%), and fruit weight (10.170%). These results are in agreement with the reports of Thulasiram et al. (2017) [17] for fruit length and Shravanthi et al. (2021) [16] for number of fruits per plant. Heritability refers to the proportion of genotypic variance in relation to phenotypic variance (total variance), reflecting the transmissible portion of variability and serving as a dependable predictor of the extent to which traits can be inherited across generations. Therefore, heritability estimates play a vital role in any crop improvement program.

In the present investigation, heritability values ranged from 37.619% to 98.150% across different traits, which aligns with the findings of Ramgiry et al. (2017) [12] . The highest heritability was recorded for number of fruits per plant (98.150%), followed by fruit yield per plant (97.385%), fruit weight (93.778%), fruit length (93.691%), number of branches per plant (93.688%), days to 50% flowering (80.798%), chlorophyll content of leaves (80.681%), fruit width (76.693%), days to first picking (74.389%), and fruit moisture content (67.884%). These results are consistent with reports by Chandramouli et al. (2016) [5] and Rambabu et al. (2019) [11] for fruit yield per plant, Alam et al. (2020) [2] for number of fruits per plant, Shravanthi et al. (2021) [16] for fruit weight, and Verma et al. (2018) [18] for fruit width. Moderate heritability was observed for plant height at 90 DAS (42.005%) and number of internodes on the main stem (37.619%), findings comparable with Acharya et al. (2015) [1] for plant height. Genetic advance as a percentage of mean (GAM) ranged from 5.141% to 59.377%. The highest GAM was observed for leaf chlorophyll content and fruit yield per plant, which agrees with results of Chandramouli et al. (2016) [5] and Priyanka et al. (2018) [10] . High GAM was also obtained for number of fruits per plant, fruit length, fruit width, fruit weight, and number of branches per plant. These results corroborate the findings of Shravanthi et al. (2021) [16] for number of fruits per plant, Mohammed et al. (2022) [8] for fruit weight, and Ramgiry et al. (2017) [12] for number of branches per plant. Moderate GAM was recorded for days to 50% flowering, while days to first picking, fruit moisture content, plant height, and number of internodes per main stem showed low GAM. Similar trends were reported by Priyanka et al. (2018) [10] for days to 50% flowering and by Chandramouli et al. (2016) [5] for days to first picking. The occurrence of high heritability coupled with high GAM, particularly for fruit yield per plant, indicates the predominance of additive gene action in the expression of these traits. Such traits are expected to respond well to phenotypic selection, offering promising opportunities for genetic improvement. These findings are in agreement with earlier studies by Chandramouli et al. (2016) [5] and Priyanka et al. (2018) [10] .

Conclusion

The study identified the genotypes Korchi, PDKV Pragati, Varsha Uphar, Phule Vimukta, and IC-42464 as superior performers for fruit yield per plant. The analysis of variance revealed significant differences among genotypes for all traits studied, confirming the existence of substantial genetic variability in the material.

The highest genotypic and phenotypic coefficients of variation were recorded for leaf chlorophyll content, followed by fruit width, fruit yield per plant, and number of branches per plant. Furthermore, high heritability estimates combined with high genetic advance were noted for fruit yield per plant, number of fruits per plant, fruit weight, fruit length, fruit width, number of branches per plant, and chlorophyll content. This combination points to additive gene action, suggesting that these traits can be effectively improved through simple selection approaches.

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