Cluster analysis of a world collection of red clover germplasm

Summary

Germplasm evaluation data on more than 800 accessions of red clover (Trifolium pratense L.) representing 41 countries of origin were examined from the Germplasm Resource and Information Network of the National Plant Germplasm System. Large variations exist for most characters over all origins. Clustering accessions using standardized values of 15 morphological and physiological descriptors produced three distinct groups that correspond to early, medium, and late maturity groups. Within each maturity group, different similarity groups were produced. The analysis revealed a large range of diversity among the red clover accessions over all origins with the most diversity occurring in accessions from Eastern and Northern Europe. Accessions with similar attributes often were from countries with contrasting agroecological conditions. Categorizing red clover accessions into similarity groups provided a structure for sampling a limited number of entries to represent the diversity of the germplasm into a core collection. The utilization of this core collection should facilitate genetic resource management and identification of genotypes for breeding and other agronomic uses.