Does Genetic Distance of Parental Forms Aff ect Specifi c Combining

Th is paper aims to probe into relationships between genetic diversity of inbred lines, estimated through the Mahalanobis distance and the eff ects of specifi c combining ability (SCA) and heterosis. Th e SCA and heterosis eff ects were analyzed for nine quantitative traits of eight inbred lines and their diallel cross hybrids of spring rape. Th e fi eld experiments (with F1 and F2 generations) were carried out in a partly balanced square design with four replications. Th e results show that the Mahalanobis distances for inbred lines and SCA eff ects of the hybrids were mostly positively correlated. However, the Mahalanobis distances were usually not related, or very weakly, with the heterosis eff ects. On this basis we conclude that it is possible that the genetic diversity of crossed lines does not have to aff ect heterosis eff ects in the hybrids derived from the crossing. Since, as far as could be determined, this is the fi rst conclusion of this type in literature, it calls for further research to study this phenomenon. Key words genetic distance, heterosis, Mahalanobis distance, phenotypic correlations, SCA, spring rap