Magnitude of genetic variability and genetic parameters for yield and quality traits in blackgram (Vigna mungo (L.) Hepper)

Introduction

Blackgram (Vigna mungo (L.) Hepper) is an important pulse crop cultivated extensively in India owing to its high protein content, nutritional value and ability to improve soil fertility through symbiotic nitrogen fixation. It plays a significant role in ensuring nutritional security, particularly in vegetarian diets. Despite its importance, the productivity of blackgram remains low due to narrow genetic base, susceptibility to biotic and abiotic stresses and limited scope for genetic improvement. Genetic variability is the basic requirement for crop improvement, as it provides the raw material for selection. Estimates of phenotypic and genotypic coefficients of variation, heritability and genetic advance help in understanding the nature and magnitude of variability and the effectiveness of selection for different traits. High heritability coupled with high genetic advance indicates the predominance of additive gene action and greater scope for improvement through selection. Hence, the present study was undertaken to assess genetic variability and genetic parameters for yield and quality traits in blackgram genotypes. Blackgram (Vigna mungo (L.) Hepper) is one of the most important pulse crops cultivated in India due to its high protein content, nutritional value and ability to improve soil fertility through biological nitrogen fixation. It is an integral component of rainfed farming systems and contributes significantly to dietary protein security. Despite its importance, the productivity of blackgram remains low, mainly due to narrow genetic base, susceptibility to biotic stresses and limited scope of selection for yield and quality traits. Assessment of genetic variability present in the germplasm is a prerequisite for any crop improvement programme. Parameters such as genotypic coefficient of variation (GCV), phenotypic coefficient of variation (PCV), heritability and genetic advance provide valuable information on the relative contribution of genetic and environmental factors in the expression of traits. High heritability coupled with high genetic advance indicates the predominance of additive gene action and effectiveness of selection. Therefore, the present study was undertaken to estimate the extent of genetic variability and genetic parameters for yield and quality traits in blackgram genotypes.

Materials and Methods

Experimental material and design

The experimental material consisted of fifty-nine blackgram genotypes, including standard checks. The experiment was conducted during the kharif 2019 season at Regional Agricultural Research station, Lam, Guntur situated at 16.10°N latitude, 28.29°E longitude and 31.5m altitude, is noted for its mean rainfall 905 mm, as well as its deep black soil with a pH 7.4, E.C 0.16 m.mhos / cm.under recommended agronomic practices. The trial was laid out in a Augmented Completely Randomized Block Design-II with four checks in 5 blocks. Standard agricultural practices of the region were adhered to in order to cultivate a healthy crop, free from insect pests and diseases. Each genotype was planted in two rows, each measuring 4 meters in length, with a spacing of 30 cm between rows and 10 cm between plants within each row.

Observations Recorded

Observations were recorded on fourteen characters, viz., days to 50 per cent flowering, days to maturity, plant height (cm), number of branches per plant, number of clusters per plant, number of pods per plant, pod length (cm), number of seeds per pod, 100-seed weight (g), seed yield per plant (g), harvest index (%), protein content (%), iron content (mg/100 g) and zinc content (mg/100 g).

Statistical Analysis

Analysis of variance was performed to test the significance of differences among genotypes. Phenotypic and genotypic coefficients of variation were estimated following Burton (1952) [2] . Broad sense heritability and genetic advance were computed as per Johnson et al. (1955) [5] . Genetic advance was expressed as percentage of mean to assess the expected response to selection.

Experimental Material and Design

The experimental material comprised fifty-nine blackgram genotypes, including released varieties and advanced breeding lines. The experiment was conducted during the kharif season at the experimental farm under recommended agronomic practices. The trial was laid out in a randomized block design (RBD) with three replications.

Observations Recorded

Data were recorded on fourteen characters, namely days to 50 per cent flowering, days to maturity, plant height (cm), number of branches per plant, number of clusters per plant, number of pods per plant, pod length (cm), number of seeds per pod, 100-seed weight (g), seed yield per plant (g), harvest index (%), protein content (%), iron content (mg/100 g) and zinc content (mg/100 g).

Statistical Analysis

Analysis of variance was carried out to test the significance of differences among genotypes. Phenotypic and genotypic coefficients of variation were calculated according to Burton (1952) [2] . Broad sense heritability was estimated as suggested by Johnson et al. (1955) [5] . Genetic advance and genetic advance as per cent of mean were computed to assess the expected response to selection.

Results and Discussion

Analysis of Variance (Table 4.1)

The analysis of variance for fourteen morpho-physiological, yield and biochemical traits is presented in Table 4.1. Mean sum of squares due to genotypes (entries) were highly significant for all the characters studied, indicating the existence of substantial genetic variability among the 59 blackgram genotypes. Significant differences among genotypes for yield and its component traits have also been reported earlier in blackgram by Panigrahi et al. (2014) [9] , Patidar and Sharma (2017) [11] and Hemalatha et al. (2018) [4] . The significance of genotypic effects for days to 50 per cent flowering, days to maturity, plant height, number of branches per plant, number of clusters per plant, number of pods per plant, pod length, seeds per pod, 100-seed weight, seed yield per plant, harvest index, protein content, iron content and zinc content clearly demonstrated wide variability in the experimental material, which can be effectively exploited for genetic improvement in blackgram, as suggested by earlier workers (Makeen et al., 2007; Priyanka et al., 2019) [7,12] .

Mean Performance of Genotypes (Table 4.2)

The mean performance of 59 blackgram genotypes for fourteen characters is presented in Table 4.2. Days to 50 per cent flowering and days to maturity showed relatively narrow ranges, indicating limited variability for phenological traits, which is in agreement with the findings of Gowsalya et al. (2016) [3] and Reddy et al. (2020) [15] . Plant height exhibited wide variation among genotypes, suggesting the presence of diverse plant types, as also reported by Kumar et al. (2014) [6] .

The number of branches per plant, clusters per plant and pods per plant showed wide variability, which directly influenced seed yield per plant. Similar associations between these yield components and seed yield have been reported earlier in blackgram by Sushmitharaj et al. (2018) [14] and Meena et al. (2021) [8] . Higher seed yield per plant recorded in genotypes such as LBG 904 and LBG 752 may be attributed to their higher number of pods and better harvest index. Moderate variability was observed for pod length, seeds per pod and 100-seed weight, which is consistent with earlier reports in blackgram and related pulse crops (Patel et al., 2015) [10] . Considerable variation was also observed for protein, iron and zinc contents, indicating the scope for improvement of nutritional quality along with yield, as reported by Singh et al. (2019) [13] and Anusha et al. (2022) [1] .

Genetic Variability, Heritability and Genetic Advance (Table 4.3)

Estimates of genetic parameters for yield and quality traits are presented in Table 4.3. In general, phenotypic coefficient of variation (PCV) was marginally higher than genotypic coefficient of variation (GCV) for all the characters, indicating the influence of environment on trait expression. However, the close correspondence between PCV and GCV values for most traits suggested that the variability was largely genetic in nature. Similar trends have been reported earlier by Johnson et al. (1955) [5] and Panigrahi et al. (2014) [9] . High PCV and GCV were recorded for seed yield per plant, plant height, number of clusters per plant, iron content and zinc content, indicating greater scope for selection. These findings are in conformity with the results reported by Hemalatha et al. (2018) [4] , Sushmitharaj et al. (2018) [14] and Meena et al. (2021) [8] in blackgram. High heritability estimates coupled with high genetic advance as per cent of mean were observed for seed yield per plant, plant height, clusters per plant, iron content and zinc content, suggesting the predominance of additive gene action. This indicates that direct selection would be effective for improvement of these traits, as reported earlier by Burton (1952) [2] and Patidar and Sharma (2017) [11] . Traits such as days to flowering and days to maturity exhibited high heritability but low genetic advance, indicating the involvement of non-additive gene action and limited response to direct selection, which is in agreement with the findings of Makeen et al. (2007) [7] and Gowsalya et al. (2016) [3] . High heritability estimates were recorded for most of the characters, particularly days to maturity (97.50%), plant height (96.00%), clusters per plant (95.70%), pods per plant (92.00%), harvest index (96.90%), iron content (98.66%) and zinc content (95.30%). High heritability coupled with high genetic advance as per cent of mean was observed for seed yield per plant (26.80%), zinc content (28.21%), iron content (25.58%), plant height (26.30%) and clusters per plant (26.67%), indicating the predominance of additive gene action and effectiveness of selection for these traits. Traits such as days to 50 per cent flowering and days to maturity, despite exhibiting high heritability, recorded low genetic advance as per cent of mean, suggesting the involvement of non-additive gene action and limited response to direct selection. Similar observations have been reported earlier in blackgram and other pulse crops.

Implications for Breeding

The results obtained from Tables 4.1 to 4.3 clearly indicate the presence of substantial genetic variability for yield and nutritional traits in blackgram. Traits exhibiting high heritability along with high genetic advance can be effectively used as selection criteria in breeding programmes aimed at improving seed yield and micronutrient content. Genotypes with superior performance for seed yield per plant and nutritional quality can be utilized as promising parents in hybridization programmes for the development of high-yielding and nutrient-rich blackgram varieties. PCV values are higher than GCV values, indicating the role of the environment in the expression of these traits. All of the evaluated traits had high heritability overall, with the exception of days to 50% flowering and days to maturity, which has high heritability but poor genetic advancement. For plant height, number of branches per plant, number of clusters per plant, number of pods per plant, harvest index, iron content, and zinc content, high heritability along with high genetic advance as percent mean was perceived, specifying the prevalence of additive gene action in the expression of the traits.

Acknowledgement

AcknowledgmentsAuthors are thankful to Indian Institute of Pulses Research, Kanpur and Regional Agricultural Research Station (RARS), Lam, Guntur are greatly acknowledged for providing blackgram germplasm and for providing resources for experiment.

References

1. Anusha, K., Reddy, K. R., Kumar, S. S. and Rao, V. S. (2022). Genetic variability and micronutrient content in blackgram (Vigna mungo (L.) Hepper). Electronic Journal of Plant Breeding, 13(2): 456-462.
2. Burton, G.W. (1952). Quantitative inheritance in grasses. Proceedings of the Sixth International Grassland Congress, 1: 277-283.
3. Gowsalya, P., Rajeshwari, S. and Muthusamy, A. (2016). Genetic variability, heritability and genetic advance for yield traits in blackgram. Legume Research, 39(4): 548-552.
4. Hemalatha, K., Lalitha, K. and Reddy, D. M. (2018). Studies on genetic variability and character association in blackgram. International Journal of Current Microbiology and Applied Sciences, 7(6): 1780-1786.
5. Johnson, H.W., Robinson, H.F. and Comstock, R.E. (1955). Estimates of genetic and environmental variability in soybean. Agronomy Journal, 47: 314-318.
6. Kumar, G. V., Reddy, P. V. and Rao, Y. K. (2014). Variability and genetic parameters for yield and yield components in blackgram. Journal of Food Legumes, 27(3): 208-211.
7. Makeen, K., Abrahim, G., Jan, A. and Singh, A. K. (2007). Genetic variability and correlations studies on yield and its components in mungbean (Vigna radiata L.). Journal of Food Legumes, 20(2): 164-167.
8. Meena, H. K., Meena, O. P. and Meena, B. L. (2021). Genetic variability and heritability studies in blackgram. Legume Research, 44(5): 561-566.
9. Panigrahi, K. K., Baisakh, B. and Mohanty, A. (2014). Genetic variability and heritability studies in blackgram (Vigna mungo (L.) Hepper). The Bioscan, 9(4): 16071610.
10. Patel, J. D., Chaudhari, P. R. and Patel, M. P. (2015). Variability and character association in blackgram. Trends in Biosciences, 8(15): 3857-3860.
11. Patidar, A. and Sharma, H. (2017). Genetic variability and heritability in blackgram. International Journal of Agriculture Sciences, 9(3): 3742-3745.
12. Priyanka, S., Singh, R. K. and Singh, B. (2019). Genetic variability for yield and yield components in blackgram. Journal of Pharmacognosy and Phytochemistry, 8(4): 1925-1929.
13. Singh, U., Praharaj, C. S. and Singh, S. S. (2019). Biofortification of pulses for nutritional security. Indian Journal of Genetics and Plant Breeding, 79(4): 673-681.
14. Sushmitharaj, D. V., Prakash, M., Ramalingam, J. and Renganayaki, P. R. (2018). Genetic variability and heritability studies in blackgram. Electronic Journal of Plant Breeding, 9(4): 1581-1586.
15. Reddy P, Sharma B, Chaudhary K. Digital literacy: A review of literature. International Journal of Technoethics (IJT). 2020 Jul 1;11(2):65-94.