Genetic Divergence in Rice

Twenty-six cultivars of photoperiod-insensitive rice comprising of both tall and semi-dwarf types were tested for genetic divergence by D² analysis for a set of six characters related to yield and fitness with a view to selecting parents for future hybridization projects. A very high degree of divergence was obtained in a number of cases. Flowering time, thousand grain weight and height were found to be the important contributors to genetic divergence. Traditional tall varieties were distinctly separated from the semi-dwarf types in the analysis. Role of natural and human selection in causing divergence among rice varieties is discussed. Future hybridization programmes are outlined.