Breeding and Genetics

Breeding for pest resistance has become a major objective of most clover breeding programs. Periodic plant introductions are a valuable source of breeders' germplasm. Introductions are received from breeding programs in other countries and from plant collection expeditions. In the United States, the annual clovers are evaluated at the Southern Regional Plant Introduction Center, Griffin, Georgia; and perennials, at the Northeast Regional Plant Introduction Center, Geneva, New York. Germplasm releases provide an important source of genetic variability. Genotypic diversity is evident from the development of numerous ecotypes in the important agronomic clover species, particularly crimson clover in the USA and subterranean clover in Australia. Variability in phenotype expressed in such ecotypes includes tolerance to acid soils, earliness of flowering, seedling vigor and seedling establishment, season of greatest vegetative growth, proportion of hard seed needed for reseeding (crimson clover), and resistance to endemic pests.