Abstract
Induction of mutation in two aromatic rice genotypes (Pigmented Mutant and IET 13541), which were developed from Gobindabhog, a short grain aromatic non-basmati rice cultivar of West Bengal, led to isolation of a number of morphologically distinct mutants, retaining the characteristic aroma of mother genotype. Genetic divergence among 18 promising mutant families in M4 generation and their two mother genotypes was assessed on the basis of 11 quantitative characters following Mahalanobis D2 statistics. Mutants and their mother lines were grouped into six clusters, of which two were solitary clusters, each containing mutant form Pigmented Mutant. The remaining four clusters contained mutants from both the mother genotypes. Distribution of the mutants derived from Pigmented Mutant into six clusters, compared with that of four clusters for mutants of IET 13541 is an indication of greater divergence among mutants of Pigmented Mutant. Mutants having prominent effects on flowering time formed separate clusters. Majority of the mutants induced at highest dose of 450Gy showed a tendency to be included in one cluster (Cluster I), while mutants from moderate dose of 350Gy formed two clusters (Clusters II and IV). Distribution of mutants, originating from the same genotype at different doses, into different clusters might be due to creation of diversity through induction of mutations. However, grouping of mutants from two different mother genotypes into one cluster could be attributed to the similar type of selection pressure exercised and common origin of both the mother genotypes, from a single variety, Gobindabhog. The intra-cluster distance was maximum (D2=106.18) in Cluster III comprising one mutant of Pigmented Mutant and two mutants of genotype IET13541. The inter-cluster distance was maximum (D2=517.51) between Clusters III and IV. Based on the analysis of genetic divergence, crosses among induced mutants including their mother lines have been suggested. Such crosses are most likely to yield a considerable amount of mutant heterosis in F1 generation and may provide a wide spectrum of recombinants for useful mutant characters in segregating generations.
