Genetic Vulnerability and Germplasm Resources of the True Clovers¹

The cultivated clovers ( Trifolium spp.) are susceptible to a wide diversity of pests, and potential vulnerability exists in part because of a lack of programs that monitor crop‐pest relationships. The trend in number and diversity of cultivars of the cultivated species is downward, perhaps because of emphasis on other crops and narrowing of gene bases by breeding. However, because the cultivated clovers are mostly cross pollinated, heterozygous, and heterogeneous we do not believe they are particularly vulnerable at present. Germplasm resources are believed to be in a more hazardous position. Although many accessions of the cultivated species have been assembled at USDA Regional Plant Introduction stations and by scientists of other agencies, the accessions have not been examined and cataloged extensively for genetic characters including pest resistance. Only a few germplasm pools are now being maintained in the cultivated species. A complete collection of the wild Trifolium species has not been assembled, and many of those once available have been lost. It is recommended that collection of species and ecotypes of Trifolium be started immediately so that variability in the genus can be preserved and analyzed. Phylogenetic studies, including interspecific hybridization in the genus, should be expanded. Methods of evaluation and use of accessions should be established by a committee of experts for the Trifolium genus so that recommendations for action can be made to a national coordinating committee concerned with germplasm resources.