Betelvine is vegetatively propagated for cultivation. Occurrence of flowering, fruiting and proper identification of male and female vines have opened up a new avenue for the improvement of betelvine through hybridization Raghavendra Rao and Maiti, (6; Maiti and Biswas, 3). A successful hybridization helps in this regard to combine desirable characters Raghavendra Rao, (7). There has been a need for launching a massive breeding programme based on genetic divergence and to develop hybrids with high heterosis followed by desirable segregants for effective selection. Keeping all these facts in view, the present study was initiated to estimate the genetic divergence present in a set of 16 genotypes of betelvine.

The investigatiqns were carried out in 16 genotypes of betelvine collected from different parts of India and maintained in the germplasm bank of the All India Co-ordinated Research Project on betelvine at Bhubaneswar. Juvenile rooted cuttings of 15 cm length were planted at a planting distance of 100 cm × 10 cm in the betelvine conservatory (bareja) in a completely randomized block design with 3 replications. A composite mixture of mustard oil cake and river bank soils was applied to the beds and irrigation as per schedule was provided. The vines were lowered for rejuvenation at an interval of 3 months. Observations on 12 quantitative trains were recoded from 6 randomly selected vines from each treatment. This was done for 2 successive years (1996–97 and 1997–98). The data collected was statistically analyse. Spectro-photometric determination of chlorophyll a and b was carried out following the procedure of Arnon (1). The genetic diversity among the genotypes was worked out using Mahalanobis' D²-sta-tistics as described by Rao (9). On the basis of the magnitude of D² values, Tocher's method was employed to group the genotypes into different clusters.

Analysis of variance revealed significant differences among the genotypes for number of laterals/vine and length of leaf indicating wide range of variability among them. Depending on the average D² values, all the 16 genotypes were grouped into 5 clusters (Table 1). The genotypes collected from the same source were found to be distributed in different clusters. Differences in genetic constitution and the presence of unabated influence of environmental factors might be resporisbile for this type of clustering pattern as suggested by Murthy and Arunachalam (5) and Rahaman et al. (8). In spite of emphasis laid by Joshi and Dhawan (2), the clustering pattern in the present study indicated that the genetic diversity was not necessarily related to geographical distribution. Further, genotypes from different geographical regions were grouped in the same cluster. This might have been due to the free exchange of propagating materials from one place to another.

The maximum intra-cluster distance was observed in cluster I, followed by III and II in the descending order (Table 2), which is the indicative of wide genetic divergence between the constituent genotypes. These constituent genotypes could be used in yield improvement through intervarietal hybridization as postulated by Mandal and Banerjee (4). The minimum intra-cluster distance was recorded by cluster II, comprising only 2 genotypes indicating gross genetic similarity between them. In this cluster, Desi Meetha Pan and Ramtek Bangla (Bangla types) had been placed together which might be due to their pedigree similarity Mandal and Banerjee, (4).

In general, the inter-cluster distance was relatively higher (Fig. 1). The cluster V was found to be a quite distinct genetic group. The highest inter-cluster value between cluster II and V can be expected to exert high heterotic effect in the hybrids when crossed and consequently may generate desirable segregants.

The cluster IV was made up of a single genotype Awani which had larger main vine length and internode length, rapid growth with least number of diseases but with short shelf-life (Table 3). On the other hand, the cluster V, a widely divergent cluster from IV was constituted by a single genotype, Kapoori which was characterized by smaller main vine and internode length, with slow growth habit but having longer shelf-life. Therefore, these 2 genotypes coming from distantly related clusters may be selected as parents for hybridization. This type of assumption has already been made by Rawat and Balasubrahmanyam (10) for evolving betelvine cultivars.

Present study has revealed that Awani of cluster IV and Kapoori of cluster V are most genetically divergent genotypes and selection involving these 2 parents would generate meaningful results. The ideal pair of clusters expected to give good combining parents for successful recombination were identified to be clusters II and V, I and V, II and III, II and IV, IV and V, and I and IV in the descending order for hybridization programme in view of their superior performance in respect of 100-leaf weight, main vine length and number of leaves/vine which are the most important yield-attributing characters for betelvine production.

Literature Cited