A Preliminary Study on the Genetic Divergence of Acacia nilotica through Seed Parameters

Reports on Acacia nilotica show that bigger seeds produce vigorous seedlings and the vigour is maintained throughout its growth period. In search of bigger seeds and of contribution of individual characteristics towards divergence, genetic divergence studies were conducted with the help of Mahalanobis's generalised D²-stalistic among 42 provenances of Acacia nilotica. Each provenance was represented by 40 random samples of seeds, from each of which seed length, seed width and seed thickness were measured in mm. The estimated V-statistic was found to be significant (1773.753) at 0.001% level of probability with 12' degrees of freedom when tested as chi-square. Cluster analysis resulted in two groups, viz, A and B, of which A was the bigger group having 34 provenances and B the smaller with 8 provenances. The divergence (inter-cluster distance) between the two groups (2 532) was found to be quite high. The inter-cluster distance was higher in A than B. The characteristic Y3 contributed towards the maximum divergence and is more than 52% whereas Y2 (33.33%) and Y1 (14.54%) were serially next. The group B contain the provenances belonging to Rajasthan only, whereas the group A included samples from all other States. It may therefore be said that the clustering pattern is not based on geographic nearness but on genetic nearness and the clustering pattern is independent of geographical distribution. It may be concluded from the study that group A is best having higher group mean values for all the three characteristics. The higher inter-cluster distance in group A indicates higher variability within the group and it is quite likely that extreme individuals from group A may help in selection. Hybridisation between widely divergent groups may also help producing greater genetic diversity which may be utilised for further selection.