Genetic Variability and Heritability Studies in Bush Cowpea (Vigna unguiculata (L.) Walp.)  

Sivakumar Vavilapalli1 , V.A. Celine1 , Shrishail Duggi2 , Sanjeev Padakipatil3 , Santoshkumar Magadum4
1. Department of Olericulture, Kerala Agricultural University, College of Agriculture, Vellayani-695522, Trivandrum, Kerala, India
2. Department of Plant Breeding and Genetics, College of Agriculture, Vellayani-695522, Trivandrum, Kerala, India
3. Department of Genetics, Agharkar Research Institute, Pune-411004, Maharashtra, India
4. Department of Genetics and Plant Breeding, G.B. Pant University of Agriculture and Technology, Pantnagar-263145, Uttarakhand, India
Author    Correspondence author
Legume Genomics and Genetics, 2013, Vol. 4, No. 4   doi: 10.5376/lgg.2013.04.0004
Received: 28 Oct., 2013    Accepted: 29 Oct., 2013    Published: 31 Oct., 2013
© 2013 BioPublisher Publishing Platform
This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Preferred citation for this article:
Shivakumar et al., 2013, Genetic Variability and Heritability Studies in Bush Cowpea (Vigna unguiculata (L.) Walp.), Legume Genomics and Genetics, Vol.4, No.4 27-31 (doi: 10.5376/lgg. 2013.04.0004)
Abstract

The present studies were carried out to assess the genetic variability, heritability and genetic advance for different characters in 22 diverse genotypes of bush cowpea. The experiment was conducted in randomized complete block design with three replications during the period 2011-2012 at the Department of Olericulture, College of Agriculture, Vellayani, Kerala, India. The analysis of variance indicated the prevalence of sufficient genetic variation among the genotypes from all the characters studied. Among the genotypes VU 6 (310.41 g) was the highest yielder. Pods per plant were highest in VU 8 (70.30) and pod weight in VU 20 (12.44 g). The high phenotypic coefficient of variation and genotypic coefficient of variation were observed for pod weight, plant height, and pod length. High heritability coupled with high genetic advance were observed for all characters studied, except days to first flowering and days to first harvest indicating these characters are governed by additive gene action. Hence, direct selection may be followed for the improvement of vegetable cowpea for these characters.

Keywords
Cowpea; Genetic advance; Germplasm; Heritability and variability

Bush cowpea (Vigna unguiculata (L) Walp.) is native of Africa. It is one of the most popular and cosmopolitan vegetable crop grown in many parts of India and elsewhere in the world. It is a rich and inexpensive source of vegetable protein. It enriches soil fertility by fixing atmospheric nitrogen. Because of its quick growth habit it has become an essential component of sustainable agriculture in marginal lands of the tropics. Cowpea popularity with farmers can be attributed to its multiple uses and its adaptability to different environments. Cowpea farmers benefit through enhanced food security, cash income, crop diversification, fodder bank, in situ grazing after harvesting in periods of year when cowpeas grain prices peak and when good quality fodder is scarce. Farmers also benefit as they use cowpea products such as boiled beans, porridge and stock feed (Nhamo & Mupangwa, 2003).

Characterization of available Germplasm is a necessary first step to facilitate breeding efforts; it especially benefits a plant breeder in choosing proper parental materials (Sarutayophat et al., 2007). To improve yield potentials in an existing crop, an understanding of the variability is necessary to formulate and accelerate breeding program (Johnson et al., 1955). Corresponding heritability, genetic advance and genotypic and phenotypic coefficient of variation within a crop will facilitate in selection of superior genotypes which is proportional to the amount of genetic variability present and the extent to which the characters are inherited. Since, many economic traits are quantitative in nature and highly influenced by the environment, the progress of breeding is governed by the nature of genetic and non-genetic variations; it will be useful to partition the overall variability into its heritable and non-heritable components to know whether superiority of selection is inherited by the progenies. Effective selection of genotypes for desirable traits is determined by the estimates of heritability along with genetic advance. Therefore, the present investigation was undertaken to estimate the variability, heritability and genetic advance in 22 bush cowpea genotypes.

Results and Discussion
All the genotypes differ significantly with respect to different characters studied. A wide range of variation was observed in all the characters. Plant height varied from 58.9 cm (VU 24) to 182.97 cm (VU 22), primary branches 5.22 (VU 19 and VU 21) to 7.44 (VU 11), days to first flowering from 31.29 (VU 6) to 38.40 (VU14), days to first harvest from 40.69 (VU 24) to 47.71 (VU 14), pod length 12.40 cm (VU 24) to 32.53 cm (VU 20), pod girth from 1.83 cm (VU 24) to 2.93 cm (VU 1), pod weight from 4.83 g (VU 24) to 12.44 g (VU 20), pods per plant from 23.35 (VU 22) to 70.30 (VU 8) and yield per plant from 150.86 g (VU 15) to 310.41 g (VU 6) (Table 1).


Table 1 Yield and yield contributing characters of 22 bush cowpea genotypes


The extent of variability present in the bush cowpea genotypes was measured in terms genetic parameters viz., genotypic and phenotypic coefficients of variation, heritability in broad sense and genetic advance along with mean and range of different characters are presented in Table 2.


Table 2 Genetic variability, heritability and genetic advance for yield and yield contributing traits in bush cowpea genotypes


In the present investigation, for majority of the characters, magnitude of GCV and PCV were closer, suggesting greater contribution of genotype rather than environment.  So, the selection can be very well based on the phenotypic values. Such a closer PCV and GCV for different characters were earlier reported by Girish et al (2006). High values of PCV with corresponding high values of GCV for plant height, pod weight, pod length, pods per plant and yield per plant which indicates that there exist high genetic variability and better scope for improvement of these characters through selection. Similar results were obtained for pod weight and yield per plant by Vidya et al (2002), and Sobha and Vahab (1998), pods per plant by Selvam et al (2000), Narayankutty et al (2003), plant height by Malarvizhi et al (2005), Girish et al (2006) and pod length by Mathura Rai et al (2004), Sobha and Vahab (1998). From the foregoing discussions, it is clear that the characters viz., pod weight, pods per plant, pod length and yield per plant offer good scope for selection in bush cowpea.

The variability existing in a population is the sum total of heritable and non-heritable components.  A high value of heritability indicates that the phenoltype of that trait strongly reflects its genotype. In the present investigation, the heritability estimates were high for all characters studied except primary branches per plant. High heritability for yield and yield attributes in bush cowpea were reported by many workers (Tyagi et al., 2000; Venkatesan et al., 2003; Suganthi and Murugan, 2008). 

Heritability estimates were high for all the characters studied. The values were especially high for plant height, Days to first harvest, pod length, pod girth, pod weight, yield of vegetable pods per plant and number of pods per plant. High heritability for vegetable pod yield and pod weight reported by Sobha and Vahab (1994) and Vidya et al (2002) supports the present findings. Further, similar to the present results, high heritability for number of pods per plant and pod length was reported by Anbumalarmathi et al (2005), Suganthi and Murugan (2007). High values of genetic advance as percentage of mean (> 20 %) were obtained in the present study for all the biometric characters studied except days to days to first flowering and first harvest.

In present study yield per plant, plant height, primary branches, pod length, pod girth pod weight and pods per plant recorded high heritability coupled with high genetic advance.  These results confirms the findings of Sobha and Vahab (1998) and Anbumalarmathi et al (2005) who reported high heritability coupled with high genetic advance for plant height, primary branches,  pod length, pods per plant and yield per plant. Johnson et al (1955) suggested that high heritability combined with high genetic advance is indicative of additive gene action and selection based on these parameters would be more reliable.

Materials and Methods
The experiment was carried out at Department of Olericulture, College of Agriculture, Vellayani (8°5' N latitude and 77°1' E longitude at an altitude of 29 m above mean sea level) during 2011-2012 with 22 bush cowpea genotypes. Soil type is a red loam belonging to Vellayani series, texturally classified as sandy clay loam. The trial was laid out in a randomized block design with three replications. Seeds were sowed at a spacing of 45 cm×30 cm. The crop received timely management practices as per the recommended package of practices to maintain a good population stand in the field.

The crop was maintained properly till last harvest and observations on growth, yield as well as yield contributing characters viz., plant height (cm), number of primary branches per plant, days to first flowering, days to first harvest, pod length (cm), pod girth (cm), pod weight (g), number of pods per plant and yield per plant (g) were recorded on five randomly selected plants in each plot at different stages of the crop. The analysis of variance was carried out and was used for calculating other genetic parameters. Genotypic coefficients of variation (GCV) and phenotypic coefficients of variation (PCV) were calculated as per the formula suggested by Comstock and Robinson (1952). Heritability in broad sense and expected genetic advance were calculated as per formula given by Allard (1960) and Johnson et al (1955) respectively.

Acknowledgements
The authors are highly grateful to the Department of Olericulture, College of Agriculture, Kerala Agricultural University, Vellayani, Thiruvananthapuram, Kerala for providing all necessary materials to carry out the present study.

Conflict of Interest
The authors declare that they have no conflict of interest.

References
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Anbumalarmathi J., Sheeba A., and Deepasankar P., 2005, Genetic variability and interrelationship studies in cowpea [Vigna unguiculata (L.) Walp.], Res. Crops, 6(3): 517-519

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