Breeding for Quantitative Characters in Linseed.—I. Utility of Diallel Crosses in the Selection of Parents

In the present investigation, the nature of genetic control of the time taken for first flowering in linseed has been studied utilizing a diallel cross involving three varieties. It has been shown that the assumptions basic to diallel analysis have been, by and large, satisfied. Estimates of a number of genetic parameters have been obtained. It is shown that the values of D (=additive genetic effects) were quite high and significant while the values of H₁ (=dominance effects) were much lower although significant. The ratio H₁/D, which measures the degree of dominance, was less than unity indicating that the genetical control of this character was mainly due to additive genetic effects and that dominance was only partial. It was also shown that dominant and recessive alleles were present in approximately equal frequencies. The dominance order among the parental arrays followed closely the parental and F₁ performance. The significance of this has been discussed. The possibility of selecting out segregants transgressing the earliest and the latest parents has been examined and it has been suggested that it may be possible to obtain segregates flowering earlier than B. 5-33 from crosses between N.P. RR 10 and B. 5-33. The draw-backs inherent in the diallel cross technique have been examined and the utility of this method in plant breeding has been discussed briefly.