The genetic basis of present breeding methods in forage crops

Abstract

For any particular species, breeding methods are largely conditioned by the stage of evolution and development of that species as a crop plant. Continued selection and isolation by man are likely to have influenced the amount of genetic variability, the mating system and the type of gene action, all of which are interdependent and together determine the applicability of any particular breeding method . Forage grasses and legumes have a relatively short history as intensively cultivated crops, and an even shorter history of directed artificial selection . As a consequence, in all the common species, there exists in the wild or semi-wild state a wide diversity of natural adaptations to climatic and edaphic conditions and to biotic systems . These vast resources of genetic variability placed the first breeders of forage crops in a fortunate position vis a vis their counterparts in crops which had achieved a narrow genetic base either by virtue of a long history of cultivation and selection (e .g. cereals) or, through recent introduction on too narrow a scale (e.g . rubber). Rapid improvement was possible and was achieved in forage crops by the application of sound ecological principles to the discovery and exploitation of naturally occurring ecotypes . While some advance may still be possible in this way, we now have to consider the best means of more rigorously tailoring genetic material to the demands of increasingly sophisticated farm systems .