Genetic variability studies in yardlong bean (Vigna unguiculata ssp. sesquipedalis L.) genotypes under hill zone of Karnataka

Introduction

Yardlong Bean (Vigna unguiculata ssp. sesquipedalis L.) is one of the most important leguminous vegetable crops. It is called as chinese long bean, string bean, snake bean, snake pea, snap pea, pea bean and asparagus bean and its chromosome number is 2n = 2x = 22. The crop is mainly cultivated for its green pods that are used as a vegetable. The crop is referred to as an underutilized leguminous crop as it is neither cultivated commercially on a big scale nor traded widely due to a lack of knowledge and improved varieties of the crop. It is widely grown in Southeast Asia, South China, Indonesia, Philippines, Taiwan, and Thailand (Rachie, 1985) [12] . Now-a-days it is being cultivated in several states of India. It is most extensively cultivated in Kerala, Karnataka, and Maharashtra. In Karnataka, it is cultivated in south-western districts like Kodagu, Belgaum, Uttara Kannada, Dakshina Kannada, Udupi, Chikkamagaluru, Hassan and some parts of Bengaluru as intercrop, mixed crop, and sole crop. In India, it is generally cultivated in an area of 18,560 -20,160 ha annually (Toppo et al., 2018) [17] . Being leguminous vegetable, it is generally valued for its nutritive value. It contains a good amount of digestible protein both in pods (23.50 -26.30%) and in leaves. Yard long beans are a good source of vitamins A and C, providing (17% and 31%) of the recommended daily allowance for these vitamins respectively. It is also rich in calcium (72.0 mg), phosphorus (59 mg), iron (2.5 mg), carotene (564 mg), thiamine (0.07 mg), riboflavin (0.09 mg) and vitamin C (24 mg) per 100 g of edible pods. It is also a good source of micronutrients containing 102.69 -120.02 mg kgˉ¹ of iron, 32.58-36.66 mg kgˉ¹ of zinc, 2.92-3.34 mg kgˉ¹ of manganese, and 0.33-0.57 mg kgˉ¹ of cobalt. It is also known as "poor man's meat" as it is an abundant and inexpensive source of digestible protein (23.5-26.3%) (Ano and Ubochi, 2008). A wide range of genetic variability is available in the yardlong bean providing good scope for improvement in yield and associated traits through selection. Performance of the genotypes differs with region, season and other growing conditions.

As a result, a prominent genotype performing well in one region may fail to perform well in other regions of different climatic conditions. Ultimately, the yield production of high quality pod depends upon the selection of suitable genotypes for a particular region (Rao et al., 1997) [14] .

Materials and Methods

The present study was conducted at the Experimental Block, Department of Vegetable Science, College of Horticulture, Mudigere, which is situated in the western ghats and represents the typical hill zone (Zone -9 and Region -V) of Karnataka and lies at 13.13° North latitude and 75.63° East longitude with an altitude of 980 m above mean sea level, during the Rabi season of 2025-26, with twenty yardlong bean genotypes (Table 1). The experiment was laid out in a Randomized Complete Block Design (RCBD) with three replications. The seeds were sown by dibbling at a spacing of 45 × 30 cm with a plot size of 2.7 × 1.5 m. Recommended cultural practices were followed throughout the crop period. Observations were recorded on growth, flowering, yield and quality parameters that include plant height (cm), internodal length (cm), number of primary branches per plant, days to first flowering, days to first harvest, days to last harvest, number of pods per cluster, pod length (cm), pod girth (mm), pod yield per plant (g), number of seeds per pod, 100 seed weight (g), total chlorophyll content (mg g⁻¹) and keeping quality (PLW). The data were subjected to analysis of variance (ANOVA) to determine the significance of differences among genotypes following Panse and Sukhatme (1957) [10] . Genotypic and phenotypic coefficients of variation (GCV and PCV) were estimated to assess the extent of variability according to Burton and Vane (1953) [3] . Heritability in broad sense (h 2 ), genetic advance (GA) and genetic advance as per cent of mean (GAM) were estimated following Johnson et al. (1955) [6] .

Results and Discussion

The analysis of variance for the different characters (Table 2) revealed significant differences among the twenty genotypes of yardlong bean for all the characters studied. The mean sum of squares due to genotypes was highly significant for most of the traits, indicating the presence of considerable genetic variability among the genotypes. The significant variation observed among the genotypes suggests that the experimental material possessed adequate variability, which could be effectively exploited for the improvement of growth, yield and quality attributes in yardlong bean. The extent of genetic variability among the twenty yardlong bean genotypes was assessed in terms of range, genotypic coefficient of variation (GCV), phenotypic coefficient of variation (PCV), heritability in broad sense, genetic advance (GA) and genetic advance as per cent of mean (GAM) (Table 3). The range of variability for plant height at 30 and 60 DAS (22.50 to 71.88 cm and 106.17 to 231.93 cm, respectively), internodal length at 30 and 60 DAS (2.59 to 4.78 cm and 9.15 to 11.85 cm, respectively), number of primary branches per plant at 30 and 60 DAS (0.76 to 3.46 cm and 1.60 to 5.27 cm, respectively), days to first flowering (50.21 to 74.37 days), days to first harvest (65.43 to 86.47 days), days to last harvest (110.13 to 115.52 days), number of pods per cluster (1.57 to 3.60), pod length (31.50 to 69.49 cm), pod girth (5.34 to 9.31 mm), pod yield per plant (160.22 to 356.56 g), number of seeds per pod (11.75 to 18.21), 100 seed weight (12.73 to 18.58 g), chlorophyll content (0.85 to 1.61 mg g⁻¹) and keeping quality (26.75 to 40.89%) indicated considerable variability among the genotypes. High GCV and PCV (>20%) were observed for plant height at 30 DAS, number of primary branches per plant at 30 and 60 DAS and pod yield per plant. High GCV and PCV indicate a greater magnitude of genetic variability for these characters. Hence, selection for these traits is expected to be effective, as the response to selection is directly associated with the extent of variability present in the experimental material. The high variability observed for pod yield and its contributing characters indicates considerable scope for their improvement through selection. Similar findings have been reported Yoseph et al. (2022) [18] in mung bean, Kusmiyati et al. (2022) [7] and Reddy et al. (2024) [15] in yardlong bean. Moderate GCV and PCV (10-20%) were recorded for plant height at 60 DAS, internodal length at 30 DAS, pod length, pod girth, number of seeds per pod, chlorophyll content and keeping quality. The moderate magnitude of variability for these characters indicates the presence of appreciable genetic variation among the genotypes. Both genetic and environmental factors may contribute to their expression, and therefore, selection for these traits may result in moderate genetic improvement. Similar observations of moderate variability were earlier reported by Devendra et al. (2011) [4] in Dolichos bean, Manggoel et al. (2012) [8] in cowpea and Airina et al. (2024) [2] in yardlong bean. Low GCV and PCV (<10%) were observed for internodal length at 60 DAS, days to first flowering, days to first harvest, days to last harvest and 100 seed weight. The low magnitude of genetic variability indicates a relatively narrow genetic base for these characters in the material studied. Consequently, selection based solely on these traits may be less effective due to limited variability available for exploitation. Similar findings were reported by Ramkumar et al. (20210) [13] and Pornsuriya et al. (2021) [11] in yardlong bean and Yoseph et al. (2022) [18] in mung bean. The study revealed high heritability coupled with high genetic advance as per cent of mean observed for plant height at early growth stage, number of primary branches per plant, pod length, pod girth, pod yield per plant and chlorophyll content. High heritability together with high genetic advance indicates the predominance of additive gene action in the inheritance of these traits. Therefore, phenotypic selection for these characters would be effective for achieving genetic improvement. Moderate heritability coupled with moderate genetic advance was observed for days to first flowering, number of seeds per pod and 100 seed weight, indicating the involvement of both additive and non-additive gene effects. In particular, the high heritability and genetic advance associated with pod yield and its important contributing traits indicate their usefulness as selection criteria for improving productivity in yardlong bean. Similar results were reported by Mesera et al. (2022) [9] in common bean, Haque et al. (2021) [5] , Sathish et al. (2023) [16] and Reddy et al. (2024) [15] in yardlong bean.

Conclusion

In conclusion, the evaluation of twenty yardlong bean genotypes revealed significant genetic variability for growth, yield and quality attributes, indicating considerable potential for crop improvement. High genotypic and phenotypic coefficients of variation, along with high heritability and genetic advance, were observed for several important yield and yield-contributing traits, suggesting good prospects for effective selection in breeding programmes. Traits such as plant height, number of primary branches per plant and pod yield per plant exhibited greater variability and heritability, indicating their importance in improving productivity. The study highlights the usefulness of the available genetic diversity for identifying and developing superior yardlong bean genotypes with improved yield and nutritional quality, thereby enhancing its commercial potential and economic value.

References

1. Anо AO, Ubochi CI. Nutrient composition of climbing and prostrate vegetable cowpea accessions. Afr J Biotech. 2008;7(20):3795-3798.
2. Airina CK. Generation mean analysis in yard long bean (Vigna unguiculata subsp. sesquipedalis (L.) Verdc.) for yield and mosaic resistance [PhD thesis]. Thrissur, Kerala, India: Kerala Agricultural University; 2024.
3. Burton GW, Vane de EM. Estimating heritability in tall fescue (Festuca arundinacea) from replicated clonal material. Agron J. 1953;45:478-481.
4. Devendra U, Mehta N, Singh J, Sahu M. Genetic divergence in dolichos bean (Dolichos lablab L.). Electron J Plant Breed. 2011;2(4):552-554.
5. Haque MS, Azad A, Saha NR, Islam MM. Genetic variability and correlation studies among yield and yield contributing characters of yardlong bean (Vigna unguiculata ssp. sesquipedalis L. Verdc.). Bangladesh J Bot. 2021;50(1):93-101.
6. Johnson HW, Robinson HF, Comstock RE. Estimate of genetic and environmental variability in soybean. Agron J. 1955;47(7):314-318.
7. Kusmiyati F, Anwar S, Herwibawa B. Study on genetic variability and heritability in F5 segregating generation for yield and its components in yardlong bean. In: Proceedings of the International Conference on Tropical Agrifood, Feed and Fuel (ICTAFF 2021); 2021. Atlantis Press; 2022. p. 44-48.
8. Manggoel W, Uguru MI, Ndam ON, Dasbak MA. Genetic variability, correlation and path coefficient analysis of some yield components of ten cowpea [Vigna unguiculata (L.) Walp.] accessions. J Plant Breed Crop Sci. 2012;4:80-86.
9. Mesera E, Shifaraw G, Alamerew S, Amsalu B. Genetic variability analysis and association of traits in common bean (Phaseolus vulgaris L.) landraces collected from Ethiopia at Jimma. Adv Agric. 2022;2022:4400711.
10. Panse VG, Sukhatme PV. The application of genetics to plant breeding. IV. The inheritance of quantitative characters and plant breeding. J Genet. 1957;40:283302.
11. Pornsuriya P, Chittawanij A. Yield stability of new elite lines of yardlong bean (Vigna unguiculata ssp. sesquipedalis). Int J Agric Technol. 2021;17(6):157165.
12. Rachie KO. Introduction. In: Singh SR, Rachie KO, editors. Cowpea research, production and utilization. Chichester: Wiley; 1985. p. xxi-xxviii.
13. Ramkumar K, Anuja S. Genetic variability, heritability and genetic advance studies in yardlong bean (Vigna unguiculata spp. sesquipedalis) genotypes. Ann Plant Soil Res. 2021;23(2):215-217.
14. Rao A, Khan MA, McNeilly T, Khan AA. Cause and effect relations of yield and yield components in rice (Oryza sativa L.). J Genet Breed. 1997;51:1-5.
15. Reddy BR, Pandey M, Singh J, Singh PM, Rai N. Principal component analysis and stability of genotypes in French bean (Phaseolus vulgaris L.). Leg Res. 2024;47(5):745-750.
16. Sathish N, Gasti VD, Rathod V, Kamble C. Studies on genetic variability and divergence in yard long bean (Vigna unguiculata ssp. sesquipedalis (L.) Verdc.) genotypes screened under polyhouse conditions. Pharma Innov J. 2023;12(3):4958-4963.
17. Toppo S, Singh D, Deepanshu. Evaluation trial in yard long bean (Vigna unguiculata ssp. sesquipedalis (L.) Verdc.) in Allahabad agro-climatic condition. G J B B. 2018;7(3):447-450.
18. Yoseph T, Mekbib F, Fenta BA, Tadele Z. Genetic variability, heritability, and genetic advance in mung bean (Vigna radiata (L.) Wilczek) genotypes. Ethiop J Crop Sci. 2022;9(2):113-135.