Breeding for Quantitative Characters in Linseed. II. Genetic Correlations and Correlated Genetic Response with Special Reference to Tillering and Earliness

The present study was undertaken to investigate the genetic association existing between flowering date and tiller number as well as between these characters and yield as also a number of yield components, in the F₂ and F₃ generations of a cross between two varieties of linseed, T. 477 and Afghanistan 2. A major objective of this cross was to transfer the high tiller number of Afg. 2 to the agronomically desirable parent, T. 477. It was also sought to predict the correlated response to be expected in the characters as a result of selection for earliness or high tiller number. It has been found that the F₃ estimates of correlation, at the genetic level, of a number of character pairs are different from the estimates obtained in the F₂ and it has been suggested that, for a number of reasons, the F₃ estimates might be more reliable. Very high positive genetic correlation was seen to exist between flowering date and tillering on the one hand and number of capsules/plant on the other in the F₃. Since capsule number is an important component of yield, this association will prove disadvantageous to the breeder. However, the association between flowering date and tiller number, though positive, is not very high and hence may be due to linkage. It may be possible, therefore, that over a period of time, through recombination and selection, the breeder might be able to select varieties combining earliness and high tiller number as well as high yield.

The extent of correlated response which would actually be met with in the F₃, if selection for flowering date and tiller number had been practiced in the F₂, has been studied. No correlated response could be convincingly demonstrated in the “ selected “ group as compared to the “ unselected “ group. However, it is likely that such responses may become visible if selection is carried on for two or three more generations.