Combining Ability and Genetic Diversity in Some Varieties of Linum Usitatissimum Murty B. R., Anand I. J. Division of Botany, Indian Agricultural Research Institute, Delhi-12 Summary A diallel set of ten varieties of linseed of diverse origin and their F1’s (without reciprocals) was analysed for combining ability for flowering time, height, height at branching, number of early and late tillers, length of early and late tillers, number of fruit-bearing branches, number of capsules per plant and seeds per five capsules. Considerable heterosis for vegetative as well as reproductive characters was observed in a majority of the F1’s with variable degrees of dominance. The crosses between the four earliest types indicated different constellations of genes for flowering time among the plants. The analysis for combining ability revealed predominantly additive gene action for flowering time, height, height at branching, and length of early tillers and mostly non-additive gene-action for the other characters. On the basis of general combining ability for all the characters, M. 10 and N. 55, both peninsular types, were the best followed by R.R. 9 and A. 17-1-1. The specific combining ability effects indicated that no cross combination was consistently good for all the characters. However, the crosses involving M. 10, N. 55, A. 17-1-1 and R.R. 9 have desirable specific combining ability effects when all yield components are considered together. The specific combining ability effects could be related in several cases to the degree of genetic divergence between the parents, although, geographical diversity did not correspond to the genetic diversity in the varieties examined. The role of predominantly non-additive gene action for practically all the yield components is discussed in relation to the limited advance for yield made in this country, adaptability to diverse ecological conditons and genetic diversity between the parents. Top |