Studies on Genetic Divergence in Cluster Bean

STUDIES ON GENETIC DIVERGENCE IN CLUSTER BEAN

[Cyamopsis tetragonoloba (L.) Taub.]

SHEELA MALAGHAN1, M. B. MADALAGERI2, V. M. GANIGER3 AND G. BHUVANESHWARI4

Department of Vegetable Science

College of Horticulture, Bagalkot

University of Horticultural Sciences, Bagalkot - 587 103, India

ABSTRACT

Sixty seven genotypes of cluster bean (Cyamopsis tetragonoloba (L.) Taub.) representing the broad spectrum of variation from various agro-climatic conditions of India were assessed for genetic divergence using Mahalanobis D2 technique. The genetic material exhibited wide range of genetic divergence for all 18 characters investigated. All the genotypes were grouped into seven clusters. The cluster II constituted maximum number (25) of genotypes followed by clusters IV 16 genotypes, VI and VII with seven genotypes each and the cluster V constituted with five genotype. The cluster VIwith seven genotypes showed maximum intra-cluster diversity (D2 = 13.003) followed by cluster II (D2 =7.778). The cluster III had minimum intracluster distance (D2=6.692). Inter - cluster distance revealed the maximum divergence between cluster VI and III (D2=50.183) closely followed by between the cluster III and II (D2= 48.804) and V and II (D2=45.711), IV and I (D2= 37.650), IV and III (D2= 36.264) and VI and V (D2=33.085).The distance between the cluster IV and II (D2= 9.909) was least. On the basis of inter-cluster distances and per se performances observed in hybridization programme for genotypes involving for specific characters can be choosen on the basis of cluster mean.

Key words: Cluster bean, Divergence, Mahalanobis, Intra-Cluster, Inter-Cluster.

1 Student, M.Sc. (Hort.) in Vegetable Science, Dept. of Vegetable Science, College of

Horticulture, Bagalkot

2 Registrar, University of Horticultural Sciences, Bagalkot

3 Associate Professor, Dept. of Vegetable Science, College of Horticulture, Bagalkot

4 Assistant Professor, Dept. of Foods and Nutrition, College of Horticulture, Bagalkot

INTRODUCTION

Cluster bean [Cyamopsis tetragonoloba (L.) Taub.] [2n=14], belongs to the family leguminaceae subfamily paplionacea. It is commonly known as guar, chavli kayi, guari, khutti etc. It is an annual with long and deep root and well adopted laterals, cultivated mainly as rainfed crop in arid and semi arid regions during rainy (kharif) seasons. It is one of the most important and potential vegetable cum industrial crop grown for its tender pods and endospermic gum (30-35 %). Guar seeds are mainly used for extraction of endospermic gum having good binding properties and have high demand in food industry as an ingredient in products like sauces and ice creams etc. In agriculture, guar gum is used as water retainer, soil aggregate and anti-crusting agent. In petroleum industry, it is used as gelling and thickening agent. Further in textile and juice industry, guar gum is used for sizing and as a thickener and stabiliser. In varnish industry, it is used as a protective colloid. In paper industry, it is used for improving quality of paper board by enhancing dry and wet strength and for enhancing sizing degree. Guar gum has also greater utility in pollution control and acts as absorbent in waste water treatment in textile industry as a flocculating and exchanging agent. In waste water purification, guar gum is used as a gelatinising agent

Despite the importance of this crop, only limited breedingwork has been done and very little attention has been given for its genetic improvement in the past, in order to enhance theproductivity levels of kharif cluster bean. The success of a breeding programme depends upon the selection of parents. It has been found that the progenies derived from crossing divergent parents give divergent and useful progenies. The D2 analysis proposed by Mahalanobis (1928) has been reported to be an effective tool to assess the genetic divergence. Such an analysis eventually helps to choose desirable parents for recombination breeding and thus results in the development of superior varieties. Ecological diversity has been regarded as a reasonable index of genetic diversity (Vavilo, 1926, Moll et al., 1962 and Ram and Panwar, 1970). Assuming this, the cultivars from widely separated localities has been included in hybridization programme by most of the plant breeders for recovering promising segregants.

MATERIAL AND METHOD

The material for the study comprised of 67 genotypes of cluster bean. The data were collected from a field experiment in randomized block design with two replications, conducted at the College of Horticulture, Bagalkot during March to June 2011. Spacing of 45 cm between rows and 20 cm between plants in a row was provided. Each genotype in each replication was represented by a single row of 3 meters length. Observations were recorded on three randomly selected plants in each plotfor eighteen characters viz.,plant height (cm), number of branches, date of first pod picking, pod length (cm), pod breadth (cm), ten fresh pod weight (g), vegetable pod yield per plant (g), clusters per plant, pods per cluster, ten dry pod weight (g), ten dry pod seed weight (g), fifty seed weight (g), seed protein content(%), seed gum content (%), seed potash content (%), seed phosphorus content (%), dry pod yield per plant (g) and seed yield per plant. Divergence was estimatedusing D2 statistic of Mahalanobis (1928) andclustering of genotypes was done according toTocher’s method as described by Rao (1952). Theper cent contribution of characters towards geneticdivergence was calculated according to Singh andChaudhary (1997)

RESULTS AND DISCUSSION

The analysis of variance revealedsignificant differences for all the charactersstudied, indicating appreciable amount ofvariability among the genotypes. All the genotypeswere grouped into seven clusters (Table 1). The cluster I had 3 genotypes followed by 25 genotypes in cluster II, 4 in cluster III, 16 in cluster IV, 5 in cluster V,7 in cluster VI and cluster VII each.A perusal of the data in this table clearly indicatedthat the genotypes usually did not cluster according totheir geographical distribution. Similar results were obtained by Pan et al., 2009 in lablab bean and Dey et al., 2007 in bitter gourd.These clusters contained genotypes either of same origin in different clusters or of different origin in same cluster, thereby, indicating no parallelism between genetic and geographic origin. Genetic drift and selection in different environments could cause greater diversity in the geographic distances (Murthy and Arunachalam, 1966).

Average intra and inter-cluster D2 values(Table 2) revealed that the intra-cluster distance was ranged from 6.692-13.003. Cluster VI with 7 genotypes showed maximum intra cluster diversity (D2=13.003) followed by cluster II (D2=7.778), IV (D2=7.750), I (D2=7.214), V (D2=6.985), VII(D2=6.932) and cluster III (D2=6.692) showing presence of diverse genotypes in these clusters.

Based on distance between clusters (inter-cluster distance), the maximum divergence was observed between cluster VI and III (D2=50.183) closely followed by between the cluster III and II (D2=48.804), V and II (D2=45.711), IV and I (D2=37.650), IV and III (D2=36.264) and VI and V (D2=33.085) which, indicated that the genotypes present in these clusters may give high heterotic response and thereby better segregants. The hybridization between genotypes of Clusters VI and III and also between genotypes of Clusters III and II and between genotypes of Clusters V and II would be very useful in generating highly diverse recombinant lines. The distance between the cluster IV and II (D2=9.909) was least. The minimum intra cluster distance was observed between cluster IV and II (D2=9.909) indicated that the genotypes of these clusters were less divergent.

The cluster mean of 67 genotypes (Table 5)showed that the mean values of the clusters varied inmagnitude for all the 18 characters. For the plant height, the highest cluster mean was observed for the cluster IV. The maximumnumber of branches per plant (12.62) was observedin Cluster V, whereas the minimum value (0.00) was found in Cluster I. Cluster VII and II recorded the minimumvalue for days to pod picking (43.43 and 43.46 days respectively). Cluster VI recorded themaximum values for days to first harvest (49.43). The pod length was highest in Cluster III(9.90 cm) whereas it was lowest in Cluster II (5.69cm). The pod width was highest in Cluster V (1.02 cm)and lowest in Cluster II (0.68 cm). The ten pod weightvalue was maximum in Cluster I and III (22.77 and 22.21g respectively) and vegetable pod yield was highest in cluster III (188.81g). For clusters per plant, the highest cluster mean was shown by the cluster IV (46.31) and cluster III (8.07) for the higher number of pods per cluster. The cluster V and cluster III had highest mean value for ten dry pod weight, ten dry pod seed weight and fifty seed weight. For seed protein content, the highest cluster mean was observed in cluster IIIfollowed by cluster V. The seed gum content wasthe maximum in Cluster VI (19.93) and the minimumin Cluster III (16.06).For seed potash content, the highest cluster mean was observed for cluster V and cluster VI.The cluster IV and cluster III had highest mean value for dry pod yield per plant and seed yield per plant. Hence, it may be concludedthat in cluster bean, there is a vast scope to develop new varieties with more yield potential and otherattributes of economic importance by using these elitegermplasm collections. To develop early varieties,selection from Cluster VII and Cluster II will be more effective and todevelop varieties having high seedweight, selection could be made from Cluster III and V. Todevelop varieties with high fresh pod weight and vegetable pod yield, selection could be made from Cluster III.

To breed varieties with high seed yield and vegetable pod yield potential, could be made from Cluster III or thehybridization between genotypes of Cluster III and IVfollowed by selection in segregating generations canbe made. To develop varieties having long, wide, selection can be exercised in Cluster V.The absence of relationship between genetic diversity and geographical distance indicates that forces otherthan geographical origin such as exchange of geneticstock, genetic drift, spontaneous variation, natural and artificial selection are responsible for genetic diversity.It may also be possible that causes of clustering patternwere much influenced by environment and genotype xenvironment interaction resulting in different expression. Another possibility may be that estimatesof diversity based on the characters used in the presentinvestigation might not have been sufficient to accountfor the variability caused by some other traits ofphysiological or biochemical nature which might havebeen important in depicting the total genetic diversityin the population. Therefore, selection of genotypesfor hybridization should be based on genetic diversityrather than geographic divergence (Mehta et al., 2004).The results of this investigation also suggested that crossing of thegenotypes having high mean yield and high intercluster distance may lead to express greater heteroticexpression and broad spectrum of favourable genetic variability in segregating generations for improvementof pod yield in cluster bean.

REFERENCES

Dey, S.S., Behera, T.K., Munshi, A.D. and Sirohi,P.S., 2007. Studies on genetic divergence in bittergourd (Momordica charantia L.). Indian J. Hort.,64:53-57.

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Table 1: Cluster composition based on D2 statistics in cluster bean

Table 2. Intracluster and interclulster D2 and D value in cluster bean

Figures in parenthesis denote corresponding 'D’ values

Table 3. The mean of 18 characters for 7 clusters in cluster bean

@ characters cluster

1. Plant height (cm) 2. Number of branches 3. Date of first pod picking 4. Pod length (cm)

1. Pod breadth (cm)6. Ten fresh pod weight (g)7. Vegetable pod yield per plant(g)8. Clusters per plant

1. Pods per cluster 10. Ten dry pod weight (g)11. Ten dry pod seed weight (g)12. Fifty seed weight (g)

1. Seed protein content(%) 14. Seed gum content (%)15. Seed potash content(%)16. Seed phosphorus content (%)

1. Dry pod yield per plant (g) 18. Seed yield per plant (g)