INTRODUCTION Clusterbean [Cyamopsis tetragonoloba (L.) Taub.] (2n=2x=14) is an underexploited legume belonging to the family Fabaceae. It is a short-day self-pollinated crop (Undersander et al., 1991), commonly known as guar, chavlikayi, guari and khutti etc. The word “guar” represents a derivation from the Sanskrit word “Gaaahar” which means cow food or fodder of livestock (Bhosle and Kothekar 2010). It is a versatile legume crop cultivated mostly as animal feed, green manure (Chudzikowski, 1971 and Siddaraju et al., 2010), green leaves as fodder, vegetable and cover crop (Arora and Pahuja, 2008). Clusterbean is grown mainly in the Kharif season. It is a photosensitive crop and requires a specific climatic condition to grow for proper germination. Due to high drought and salinity tolerance (Francois et al., 1990) and (Ashraf et al., 2005), guar could be a valuable alternative crop for the exploitation of semi-arid environments. It grows best in sandy soils, with a rainfall range of 250 to 450 mm and a temperature range of 25°C to 40°C. The optimum pH value is between 7 to 8, guar enhances soil productiveness by fixing atmospheric nitrogen for its necessity and also for the succeeding crop (Bewal et al., 2009). Gillette (1958) divided the genus Cyamopsis into three races, viz., Cyamopsis tetragonoloba (L.) Taub, Cyamopsis senegalensis Guill. and Perr. and Cyamopsis serrata Schinz. The haploid and diploid chromosome numbers of all three genus species of Cyamopsis were reported to be n = 7 and 2n = 14. Gillete (1958) suggested that the most probable origin of clusterbean in Africa is due to the presence of many wild relatives in Africa. C. tetragonoloba seeds are almost round. At maturity, C. senegalensis and C. serrata also exhibit pod shattering, although C. tetragonoloba does not (Menon, 1973). From the outside to the inside of the dicotyledonous seed of the clusterbean, three primary portions are present: the husk or hull (14–17%), the endosperm (35–42%), and the germ or embryo (43–47 percent). In contrast to most other legumes, the clusterbean seed has a very big endosperm. When processing clusterbean seeds for gum, dull-white, wrinkle-free seeds are desirable; black seeds are said to provide inferior gum (Bhatia et al., 1979; Hymowitz and Matlock 1963). In India, guar is being grown mainly in arid and semi-arid regions of North-Western states of Rajasthan, Gujarat, Haryana, Punjab, parts of Uttar Pradesh, Madhya Pradesh and Tamil Nadu. Rajasthan occupies the largest area under guar cultivation (82.1%), followed by Haryana (8.6%), Gujarat (8.3%) and Punjab (1%) which in turn produced 64, 22, 12 and 2 percent guar seeds, respectively (Pathak et al., 2010). In, Gujarat is mainly grown in Banashkantha, Mahesana, Ahmedabad, Anand, Kheda, Gandhinagar, and Kutch districts. The cultivated area under guar in Gujarat was 1.23 lakh ha with a production of 0.86 lakh tonnes and productivity of 699.4 kg/ha (Anonymous, 2021). The genetic resources of guar have been employed to raise agricultural yield potential, broaden adaption, develop tolerance to disease, and pest stress, and improve quality and stature. The main genetic support for the crops comes from their wild relatives, who also assist in preserving their prized status. Superior genotypes of clusterbean have been released as a result of the choices made through local landraces (Henry et al., 1992; Bharodia et al., 1993; Mishra et al., 2009). Branched or unbranched plant types, hairy or smooth stems, straight or sickle-shaped pods, pubescent or glabrous leaves, determinate or indeterminate development, and regular or irregular pod-bearing behaviors are only a few of the many variations in the known clusterbean germplasm (Saini et al., 1981). According to Ogwu et al. (2014), one of the most sustainable ways to preserve priceless genetic resources while simultaneously increasing agricultural output and food security are to use a variety of germplasms to improve crops. For this reason, the present study was carried out to evaluate genetic diversity in this priceless legume crop. MATERIALS AND METHOD The present investigation was carried out with thirty diverse clusterbean genotypes (Table 1) received from Pulses Research Station, Sardarkrushinagarand evaluated with four replications in Randomized Block Design (RBD) during Kharif 2020-21 at Agronomy Instructional Farm, S. D. Agricultural University, Sardarkrushinagar, Gujrat. The center is situated 24˚-19'North latitude and 72˚-19’ East latitude with an elevation of 154.52 meters above mean sea level and represents the North Gujarat Agro-climatic region. The general view of the experimental site is depicted in (Fig. 1). Climatic conditions during the experimental period at present in Table 2 and Fig. 2. Observations from five randomly selected plants of each genotype in each replication were recorded on nine quantitative [days to flowering, plant height (cm), number of branches per plant, number of pod per plant, pod length (cm), days to maturity, number of seed per pod, test weight (g) and seed yield per plant (g)] and two biochemical characters [gum content (%) and protein content (%)]. Each genotype was represented by a single row of 4.0 m in length. The inter and intra-row distances were 45 cm and 15 cm, respectively. The mean performance of each genotype for all traits was subjected to statistical analysis. The analysis was carried out by the Mahalanobis D2 technique (Mahalanobis, 1936). The genotypes were grouped into different clusters following Tocher’s method as described by Rao (1952). RESULTS AND DISCUSSION The foundational element for a successful breeding program is genetic diversity. Any program must include the collection and evaluation of germplasm lines and genotypes of every crop, which increases the potential for utilizing genetic diversity. The Mahalanobis D2 method (Mahalanobis, 1936) is a potent instrument for calculating the genetic divergence among a group of genotypes. A. Distribution of genotypes evaluated for seed yield into different clusters Tocher's approach (Rao, 1952) was used to group the genotypes, with the underlying premise that genotypes within a cluster had lower D2 values among themselves than those from groups belonging to other clusters. From 30 genotypes, five clusters all emerged. Table 3, displays the genotype distributions into five groupings. With eleven genotypes, Cluster II was the largest cluster, followed by Cluster I, which had ten genotypes. Clusters IV and V each have one genotype, while Cluster III has seven genotypes. Remzeena et al. (2018) noted a comparable genotype distribution. B. Average Intra and inter-cluster D2 value Intra cluster average D2 values ranged from 0.00 to 113.21. (Table 4) Among the clusters, cluster II had the maximum intra-cluster distance (D2 = 113.21), followed by cluster III (D2 = 109.96) and cluster I (D2 = 109.49). The zero intra-clusters distance was observed for clusters IV and V (D2 = 0.00). The maximum inter-cluster distance was recorded between cluster II and cluster IV (D2 = 558.37) followed by that between III and IV (D2 = 494.20), while the minimum inter-cluster distance was observed between clusters I and IV (D2 = 209.26). Inter-cluster distances were higher than intra-cluster distances which indicated the existence of substantial diversity among the genotypes. The selection of parents for crossing from divergent clusters may result in heterotic expression for yield and quality traits. Similar observations were recorded by Kumar et al. (2014). C. Cluster means seed yield and its components traits The mean performance of clusters for eleven characters is presented in (Table 5). Cluster III had the highest cluster mean for days to flowering (46.79), days to maturity (101.04) and plant height (40.83). Cluster IV had the highest cluster mean for the number of branches per plant (5.10), gum content (28.23) and protein content (26.68). Cluster V had the highest cluster mean for the number of pods per plant (39.50), pod length (5.20), test weight (2.99) and seed yield per plant (7.43). Similar observations were recorded by Kumar et al. (2014). D. The relative contribution of different characters toward genetic diversity The components of D2 due to each character variable were ranked ascending to the highest value. The total of these ranks over all possible [n (n − 1)/2] = 435 combinations would provide indirect information about the order of priority in terms of the percentage contribution of the character to the total divergence. These percentages are presented in (Table 6). Among all the characters, gum content (42.30 %) contributed the maximum to the diversity by taking the first rank 184 times out of 435 combinations, followed by days to flowering (28.28 %) with 123 times, the number of pods per plant (13.33 %) with 58 times, days to maturity (7.82 %) with 34 times. While, protein content (4.14 %) with 18-time, number of branches per plant (3.45) 15 times, number of seeds per pod (0.23 %) with one time, test weight (0.23 %) with one time and plant height (0.23 %) with one time. While characters like the pod length and seed yield per plant contributed null towards the total genetic divergence. In the present study, gum content (42.30 %), days to flowering (28.28 %) and the number of pods per plant (13.33 %) were the main contributors to the total divergence. These traits may play important role in germplasm collection and evaluation. Remzeena et al. (2018) also observed high diversity for days to flowering and moderate to low contribution towards the total divergence, for days to maturity, protein content, number of branches per plant, plant height, number of seeds per pod and test weight; Shekhawat and Choudhary (2004) for days to flowering and Wankhade et al. (2017) for gum content.