Division of Genetics, Indian Agricultural Research Institute, New Delhi-12
*Results based on thesis submitted in partial fulfilment of the requirements for Ph.D. (Agra University) by M. K. Upadhyay.
A quantitative assessment of genetic diversity for a set of characters related to productivity and survival was undertaken in a world collection of Pennisetum typhoides from fourteen geographical regions, under non-stress and stress environments utilising multivariate analysis. The investigations brought out the presence of enormous genetic diversity for important components of fitness among and within the geographical regions. The studies indicated that genetic diversity and geographical diversity were not necessarily related. Genetic drift and selection under different environments could have caused greater divergence than geographical distance as was evident in Indian Pennisetums.
The multivariate analysis revealed considerable similarities in the composition of clusters of fourteen geographical regions under the two environments. The results indicated that considerable diversity exists in the East and West African regions both for vegetative and reproductive characters. The Indian germ plasm was distinctly diverse from all other geographical groups and formed separate clusters under both the environments.
It was also observed that vegetative characters such as height and flowering were more important factors in differentiation among the germ plasm from different geographial regions while ear characters were more potent factors for differentiation among genotypes.
The results of the multivariate analysis of seventy representative genetic stocks revealed considerable differences in the composition of clusters under non-stress and stress conditions. The present study brought out the need of an optimum environment for the fullest expression of the genotype for obtaining a realistic picture of genetic divergence as estimated by D2 statistic.
