Breeding for creeping root in lucerne (Medicago sativa L.). I. The inital response to selection

Abstract

A lucerne-breeding programme was initiated in Canberra to combine the creeping-rooted habit of the variety Rambler with the summer and winter vigour of the varieties Hunter River, Hairy Peruvian, and African. The incidence of creeping-rooted plants in the "F₁" generation was only 5%, which indicated marked non-additive gene effects concerned with the expression of the character. An "F₂" generation, formed by interbreeding creeping plants from the "F₁", showed only 6% of creeping individuals. Selection and recombination of the available creepers resulted in an average of 41% creeping-rooted plants in the "F₃" families, with a range between families from 0 to 81%. In the "F₂" generation approximately 50% of the phenotypic variance for creeping root was found to be additive genetic, and the response to selection was high. However, the persistence of non-additive genetic effects was indicated by a statistical analysis of the '"F₃" generation. The genotypic correlation coefficients between creeping and summer forage scores, and creeping and winter forage scores, were –0.09 and 0.59 respectively, and that between summer and winter forage scores was 0.48. Thus an association between creeping rootedness and plant vigour is possible. For Rambler, both the incidence and degree of creep were found to be intensified by short days and low temperature, but this effect was not so apparent in the breeding material used in this study.