Assessment of Genetic Divergence in among Yard Long Bean (Vigna unguiculata subsp. sesquipedalis [L.]) Genotypes  

Siva Kumar Vavilapalli1 , Celine V.A.2 , Vahab A.M2
1. Department of Horticulture, Dr. Y.S.R. Horticultural University, Tadepalligudem, West Godavari- 534101, A.P., India
2. Department of Olericulture, Kerala Agricultural University, College of Agriculture, Vellayani-695522, Trivandrum, Kerala, India
Author    Correspondence author
Legume Genomics and Genetics, 2014, Vol. 5, No. 1   doi: 10.5376/lgg.2014.05.0001
Received: 12 Jan., 2014    Accepted: 13 Mar., 2014    Published: 14 Jun., 2014
© 2014 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.
Abstract

Forty four genotypes of yard long bean (Vigna unguiculata subsp. sesquipedalis (L.) Verd.) were investigated to understand the extent of genetic diversity through twelve quantitative traits. Mahalanobis’s D2 analysis established the presence of wide genetic diversity among these genotypes by the formation of 3 clusters. Cluster I had the maximum number of genotypes i.e 34 and cluster III had only four genotypes. Intra cluster distance analysis revealed that the minimum intra cluster distance was observed in the cluster I. The  inter-cluster  distance  (D)  was  found  to  be  the  maximum  between  the  clusters  II  and  III  and  the same  was minimum  between  clusters  I and  II. The results indicated that 100 seed weight contributed maximum to the total divergence followed by pod yield per plant. Intercrossing among the genotypes belonging to cluster II, V and IV was suggested to develop high yielding varieties with other desirable characters or may be used as potential donors for future hybridization programme to develop superior yard long bean variety with good consumer preference and high pod yield.

Keywords
D2 statistics; Genetic diversity; Vigna unguiculata ssp. sesquipedalis; Yard long bean

Background
Yard long bean (Vigna unguiculata ssp. sesquipedalis [L.]Verde.) is a distinct form of cowpea grown as a vegetable crop in southern Asia and the Far East for its immature pods, which are used as a vegetable. It is one of the most popular and cosmopolitan vegetable crop grown in many parts of India. Yard long bean is also considered to be one of the most important vegetable crops in parts of Indonesia, Thailand, Philippine, Taiwan and China. It is an important tropical Indian pulse and vegetable crop covering an area of about 7.7 million ha. 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. The yard long bean is a nutritious vegetable, which supplies protein (3.5 g), 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. This crop meets greater demand of the vegetable especially in South India and some parts of north India. The productivity of this crop is low (3qha-1) which needs improvement through systematic breeding programmes (Yadav et al., 2004).
Genetic diversity is the basic requirement for a successful breeding programme. Collection and evaluation of genotypes of any crop is a pre-requisite for any programme, which provides a greater scope for exploiting genetic diversity. A quantitative assessment of the genetic divergence among the collection of germplasm and their relative contribution of different traits towards the genetic divergence provide essential and effective information to breeder in his hybridization programme and thereby genetic improvement of yield. The necessity for finding out genetic divergence among the types is more pronounced because of two reasons i.e., i) genetically diverse parents if included in the hybridization programme are likely to produce high heterotic effect; ii) a wide spectrum of variability could be expected in the segregating generation of crosses involving distantly related parents.
Table 1 Distribution of 44 genotypes of yard long bean into three clusters
Cluster
Number of genotypes
Name of the genotypes
I
34
VS 2,VS 3,VS 5, VS 6, VS 7, VS 8, VS 10, VS 11, VS 12, VS 13, VS 14, VS 15, VS 16, VS18,VS 19, VS 21, VS 22, VS24, VS27,VS 29, VS30, VS 33, VS 34, VS 35, VS 36, VS 37, VS 39, VS 40, VS 41, VS 42, VS 43, VS 44, VS 46, VS 47
II
6
VS 1, VS 4, VS 20, VS 23, VS 31, VS 32
III
4
VS 9, VS 28, VS 38, VS 45
 
Results and Discussion
By the application of clustering technique, 44 genotypes were classified into three clusters (Table 1). The cluster I was the largest having 34 genotypes. Cluster II consisted of six genotypes followed by cluster III with four genotypes. The average intra and inter cluster distances are presented in Table 2. The divergence of each cluster from other clusters (inter cluster distance) indicated high order of divergence between cluster II and III followed by cluster I and III. Thus hybridization between genotypes from these clusters should result in maximum hybrid vigour and higher number of useful segregants. This finding is in agreement with the results of the study conducted by Valarmathi et al., 2007.
 
Table 2 Inter and intra (diagonal) cluster values of average of D2 and D values (in bold)
 
Cluster I
Cluster II
Cluster III
Cluster I
19.91
38.88
40.18
Cluster II
 
22.73
69.08
Cluster III
 
 
26.30
The twelve cluster means for all the nine characters are given in Table 3. Wide ranges of mean values among the clusters were noticed for all the characters studied. Clusters III had the highest value for the characters viz., vine length (512.29), primary branches per plant (4.92), petiole length (8.98 cm), pod length (58.98 cm), pod girth (3.52 cm), pod weight (36.17) and 100 seed weight (19.52 g). Clusters I had the highest value for the characters viz., peduncle length (14.83), seed per pod (19.30), and days to flowering (38.01). This means cluster I had late bearing genotypes. Clusters II had the highest value for yield per plant (870.05g) and pod per plant (63.17). The lowest mean value for days to flowering was recorded in cluster II (36.50).Similar finding were observed by Sugathi et al., 2007 and Nagalakshmi et al., 2010.
In the present investigation to assess the percentage contribution of different important traits towards the genetic divergence are calculated Table 4. Among the characters that contributed to genetic divergence the maximum contribution of 79.94% was recorded by 100 seed weight followed by pod yield per plant (9.92%). Remaining characters had very less contribution to genetic diversity. Primary branches/plant and pods per plant had no contribution to diversity. Similar studies were conducted by Narayanankutty et al., 2005; Sulathi et al., 2007.
Table 3 Cluster means for twelve characters in 44 diverse accessions of yard long bean
 
1
2
3
4
5
6
7
8
9
10
11
12
Cluster I
446.89
4.80
8.74
38.01
14.83
47.52
3.04
20.87
19.30
15.91
56.69
757.49
Cluster II
429.38
4.82
8.75
36.50
14.59
44.32
3.32
23.34
17.56
12.04
63.17
870.05
Cluster III
512.29
4.92
8.98
37.92
13.89
58.98
3.52
36.17
17.50
19.52
39.83
763.85
Note: 1 Vine length (cm); 2 Primary branches/plan; 3 Petiole length (cm); 4 Days to flowering; 5 Peduncle length (cm); 6 Pod length (cm); 7 Pod girth (cm); 8 Pod weight (g); 9 Seeds per pod; 10 100 Seed weight (g); 11 Pods per plant; 12 Pod Yield per plant (g)
Table 4 Relative contribution of twelve characters towards genetic divergence in 44 yard long bean germplasm
S. NO
Characters
Number of times ranked first
Contribution
1
Vine lenth (cm)
12
1.27
2
Primary branches/plant
0
0.00
3
Petiole length (cm)
1
0.11
4
Days to flowering
8
0.85
5
Peduncle length cm)
5
0.53
6
Pod length (cm)
28
2.96
7
Pod girth (cm)
14
1.48
8
Pod weight (g)
23
2.43
9
Seeds per pod
5
0.53
10
100 Seed weight (g)
756
79.92
11
Pods per plant
0
0.00
12
Pod yield per plant (g)
94
9.94
 
Total
946
100
 
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.
References
Nagalakshmi R.M., Usha Kumari R., and Boranayaka M.B., 2010, Assessment of genetic diversity in cowpea (Vigna unguiculata), Electronic J. Plant Breeding, 1(4): 453-461
Narayanankutty C., Sunanda C.K., and Jaikumaran U., 2005, Genetic divergence in pole type vegetable cowpea, Indian J. Horticulture, 62(4): 354-357
Suganthi S., S. Murugan and M. Venkatesan, 2007, D2 analysis in cowpea (Vigna unguiculata (L.) Walp.), Legume Res., 30(2): 145-147
Sulnathi G., Prasanthi L., and Reddy Sekhar M., 2007, Character contribution to diversity in cowpea, Legume Res., 30(1): 70-72
Valarmathi G., Surendran C., and Muthiah A.R., 2007, Genetic divergence analysis in subspecies of cowpea (Vigna unguiculata ssp. unguiculata and Vigna unguiculata ssp. sesquipedalis), Legume Res., 30(3): 192-196
Yadav K.S., Yadava H.S., and Naik M.L., 2004, Gene action governing the inheritance of pod yield in cowpea, Legume Res., 27(1): 66-69

 

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