Assessment of heterosis for growth parameters in anthocyanin-rich okra (Abelmoschus esculentus L.) hybrids

Introduction

Okra [Abelmoschus esculentus (L.)], belonging to the family Malvaceae (2n = 130), is an important warm-season vegetable crop cultivated throughout the tropical and subtropical regions of the world. It is valued for its tender immature fruits, which are rich in dietary fibre, vitamins, minerals, proteins, mucilage and bioactive compounds that contribute significantly to human nutrition and health (Gemede et al., 2015) [6] . India is the leading producer of okra, accounting for a major share of global production due to its favourable agro-climatic conditions and widespread cultivation. In addition to its nutritional importance, okra possesses medicinal properties owing to the presence of antioxidants, phenolic compounds and mucilage, which exhibit antidiabetic, antimicrobial and anti-inflammatory activities.

Recently, coloured or anthocyanin-rich okra genotypes have gained considerable attention because of their high anthocyanin content, which imparts attractive red to purple pigmentation and enhances the antioxidant potential of the fruits (Zhang et al., 2021) [20] . Anthocyanins are natural flavonoid pigments associated with reduced oxidative stress and protection against several chronic diseases, thereby increasing the nutritional and commercial value of coloured okra. The utilization of anthocyanin-rich genotypes in hybrid breeding offers an opportunity to combine superior nutritional quality with improved agronomic performance. Despite its economic importance, the productivity of okra remains constrained by the limited genetic potential of many cultivated varieties and their susceptibility to biotic and abiotic stresses. Development of high-performing hybrids through heterosis breeding has become an effective strategy for improving crop performance.

Heterosis or hybrid vigour, refers to the superior performance of F₁ hybrids over their parents and has been widely exploited in okra to enhance vegetative growth, earliness, yield and adaptability. The expression of heterosis is mainly attributed to favourable dominance and nonadditive gene interactions, which can be effectively utilized to develop superior hybrids. Growth parameters such as plant height, number of branches per plant, stem girth, internodal length, days to 50 percent flowering and days to first fruit harvest are important determinants of plant vigour and productivity in okra. Vigorous vegetative growth promotes efficient light interception, improved photosynthetic activity and greater assimilate production, while early flowering and harvesting enable early market supply and increased cropping efficiency. Therefore, the assessment of heterosis for these growth traits provides valuable information for identifying promising hybrid combinations suitable for commercial cultivation and future breeding programmes. Keeping these aspects in view, the present investigation was undertaken to assess the magnitude and direction of heterosis for important growth parameters in anthocyaninrich okra (Abelmoschus esculentus L.) hybrids. The study aimed to identify superior hybrid combinations exhibiting enhanced vegetative growth and earliness that could serve as potential genetic resources for the development of highperforming anthocyanin-rich okra hybrids.

Materials and Methods

The present investigation was conducted at the Department of Vegetable Science, College of Horticulture, Hiriyur, Karnataka, during the year 2025-26. The experimental material consisted of six diverse okra parental genotypes, namely Red Okra, Double Colour Okra, Harihara Local, Kashi Lalima, CP-104-15-6 and AP-77-7-29 (Table 1.). The six parental genotypes were crossed in a half-diallel mating design (excluding reciprocals) to generate fifteen F₁ hybrids. The parents, F₁ hybrids and two standard checks (Arka Nikita and Pusa Lal Bhindi-1) were evaluated in a Randomized Complete Block Design (RCBD) with three replications. Each experimental plot consisted of 15 plants spaced at 60 cm between rows and 30 cm between plants. Agronomic practices including irrigation, weeding, and pest management were applied uniformly across all plots. Observations were recorded on five randomly selected plants from each plot for six growth parameters, namely plant height (cm), number of branches per plant, stem girth (cm), internodal length (cm), days to 50 percent flowering and days to first fruit harvest.

Statistical Analysis

The experimental data were analysed by analysis of variance (ANOVA) for a Randomized Complete Block Design (RCBD) following the procedure of Panse and Sukhatme (1985). Heterosis was estimated as mid-parent heterosis, better parent heterosis and standard heterosis over the two commercial checks (Arka Nikita and Pusa Lal Bhindi-1) following the method of Fonseca and Patterson (1968). Superior hybrids were identified based on the magnitude of desirable heterosis for the growth parameters evaluated and their performance relative to the standard checks.

Results and Discussion

Per se performance

The analysis of variance revealed significant differences among the genotypes for all six traits, indicating the presence of substantial genetic variability and scope for hybrid improvement in okra (Table 2 and3). Significant differences among parents were observed for number of branches per plant and stem girth, whereas plant height, internodal length, days to 50 percent flowering and days to first fruit harvest showed comparatively lower variation among the parents. Significant variation among hybrids for number of branches per plant, stem girth, internodal length and days to 50 percent flowering indicated ample scope for exploiting heterosis in anthocyanin-rich okra breeding. Furthermore, the significant differences between parents and hybrids for all the growth parameters confirmed the expression of hybrid vigour and the existence of considerable genetic divergence among the parental lines. Similar findings were reported by Dhall et al. (2003) [4] , Darshini and Pujar (2022) [3] , Ranga et al. (2024) [15] and Keerthana et al. (2025) [8] .

Heterosis

Considerable variation in heterosis was observed among the fifteen F₁ hybrids for all the growth parameters studied (Table 4 [11] , Chavan et al. (2021) [2] and Ajit et al. (2024) [1] . Number of branches per plant exhibited considerable heterotic variation among the hybrids. Twelve hybrids exhibited positive mid-parent heterosis, whereas nine hybrids exhibited positive better parent heterosis. The hybrid Harihara Local × Kashi Lalima recorded the highest heterosis over the mid-parent (55.05%), better parent (40.83%) and both standard checks, followed by Red Okra × Kashi Lalima. Increased branching enhances canopy development and provides more sites for flowering and fruit production, making positive heterosis desirable for this trait. These findings are in agreement with those of Patel et al.

(2016) [14] , Jakasania (2022) [7] and Ajit et al. (2024) [1] . [12] . Internodal length exhibited significant heterotic effects in both directions, although negative heterosis was considered desirable as shorter internodes contribute to compact plants with increased fruit-bearing nodes. Several hybrids exhibited significant negative heterosis over the mid-parent, better parent and standard checks, indicating the effectiveness of complementary parental interactions in reducing internodal length. Similar observations were reported by Panchal et al. (2021) [12] and Koli et al. (2020) [9] . Days to 50 percent flowering exhibited significant negative heterosis among the hybrids evaluated. All fifteen hybrids expressed desirable negative mid-parent and better-parent heterosis. The hybrid Harihara Local × Kashi Lalima recorded the highest negative heterosis over the mid-parent (-9.02%), better parent (-10.59%), Arka Nikita (-10.97%) and Pusa Lal Bhindi-1 (-11.73%). The consistent expression of negative heterosis indicates the predominance of nonadditive gene effects governing flowering time. Early flowering is a desirable attribute in okra as it contributes to earliness and can increase the effective harvesting period. Similar results have been reported by Sapavadiya et al.

(2019) [16] , Suganthi et al. (2019) [18] . Days to first fruit harvest exhibited significant negative heterosis over the better parent and standard checks. [11] , Shwetha et al. (2021) [17] and Vekariya et al. (2019) [19] .

Conclusion

The present study revealed significant heterotic expression for the growth parameters of anthocyanin-rich okra, indicating the presence of substantial genetic variability among the parental lines. Desirable positive heterosis was observed for plant height, number of branches per plant and stem girth, whereas significant negative heterosis for internodal length, days to 50 percent flowering and days to first fruit harvest indicated the potential for developing compact and early-maturing hybrids. Among the hybrids evaluated, Harihara Local × Kashi Lalima consistently exhibited superior heterotic performance for most of the growth traits, followed by Red Okra × Kashi Lalima. The predominance of non-additive gene action governing these traits suggests that heterosis breeding can be effectively exploited for the development of vigorous, early and anthocyanin-rich okra hybrids with improved agronomic performance.

References

1. Ajit K, Bahadur V, Lal GM. Study on genetic variability and correlation in okra (Abelmoschus esculentus L.). International Journal of Research in Agronomy. 2024;7(5):125-128.
2. Moench]. International Journal of Agricultural Sciences. 2022;18:359-365.
3. Dhall RK, Dhall SP, Singh K. Studies on heterosis in okra (Abelmoschus esculentus L. Moench). Journal of Research, Punjab Agricultural University. 2003;40(1):9-15.
4. Fonseca S, Patterson F. Hybrid vigour in a seven parent diallel cross in common winter wheat (Triticum aestivum L.). Crop Science. 1968;8:85-88.
5. Gemede HF, Ratta N, Haki GD, Woldegiorgis AZ, Beyene F. Nutritional quality and health benefits of okra (Abelmoschus esculentus): A review. Food Science and Quality Management. 2015;33:87-96.
6. Keerthana S, Joshi JL, Selvam YA, Ruban S. Heterosis and combining ability in okra [Abelmoschus esculentus (L.) Moench] via line × tester design. Biochemistry and Cellular Archives. 2024;24(1):1371-1541.
7. Koli HK, Patel AI, Vshai JM, Chaudhari BN. Study of heterosis for fruit yield and its component traits in okra [Abelmoschus esculentus (L.) Moench]. International Journal of Current Microbiology and Applied Sciences. 2020;9(9):1930-1937.
8. Kumar R, Kumar GS. Identification of best hybrid combination for fruit yield and its component traits in okra [Abelmoschus esculentus (L.) Moench]. Journal of Pharmacognosy and Phytochemistry. 2019;8(1):18751877.
9. Mundhe SS, Pole SP, Khandebharad PR, Patil AR. Heterosis studies for yield and yield component traits in okra (Abelmoschus esculentus (L.) Moench). Pharma Innovation Journal. 2022;12:837-842.
10. Panchal KN, Bhalekar MN, Kshirsagar DB, Joshi VR, Kute NS. Heterosis for fruit yield and its component traits in okra (Abelmoschus esculentus L. Moench). Pharma Innovation Journal. 2021;10(8):1192-1200.
11. Panse VG, Sukhatme PV. Statistical Methods for Agricultural Workers. 4th ed. New Delhi: ICAR Publications; 1985.
12. Patel BG, Patel AI. Heterosis studies in okra [Abelmoschus esculentus (L.) Moench]. Annals of Agriculture and Environmental Science. 2016;1(1):1520.
13. Ranga AD, Vikram A, Kumar R, Dogra RK, Sharma R, Sharma HR. Exploitation of heterosis and combining ability potential for improvement in okra (Abelmoschus esculentus L.). Scientific Reports. 2024;14(1):24539.
14. Sapavadiya SB, Kachhadia VH, Savaliya JJ, Sapovadiya MH, Shekhawat VS. Heterosis studies in okra (Abelmoschus esculentus (L.) Moench). Pharma Innovation Journal. 2019;8:408-411.
15. Shwetha A, Mulge R, Khot RK. Heterosis studies in okra [Abelmoschus esculentus (L.) Moench] for growth and earliness parameters through half diallel analysis. Pharma Innovation Journal. 2021;10(6):1250-1254.
16. Suganthi S, Sathiskumar P, Kamaraj A, Shanmugapriya R. Exploitation of heterosis through diallel analysis in International Journal of Advanced Biochemistry Research https://www.biochemjournal.com bhendi [Abelmoschus esculentus (L.) Moench]. Journal of Pharmacognosy and Phytochemistry. 2019;2:598601.
17. Moench]. International Journal of Chemical Studies. 2019;7:484-490.
18. Zhang Y, Zhang T, Zhao Q, Xie X, Li Y, Chen Q, et al. Comparative transcriptome analysis of the accumulation of anthocyanins revealed the underlying metabolic and molecular mechanisms of purple pod coloration in okra (Abelmoschus esculentus L.). Foods. 2021;10(9):2180.