Characterization of the United States germplasm collection of zigzag clover (Trifolium medium L.)

Abstract

The United States germplasm collection of zigzag clover,Trifolium medium L. was evaluated for chromosome number and latitude of collection site to determine their relationship to forage and seed yield and other agronomic characters. The objective was to locate optimum sites for future collection of high forage- and seed-yielding genotypes. Chromosome numbers ofT. medium var sarosiense were uniformly hexaploid (2n = 48) butT. medium varmedium ranged from 64 to 80, with decaploids more frequent in the collection than octoploids. No numbers intermediate between the hexaploid (2n = 8x = 48) and the octoploid (2n = 6x = 64) were found though intermediates have been reported in other studies. Chromo some numbers were only weakly related to latitudes of collection sites. Correlation data suggested that accessions with high chromosome numbers tended to be strongly leafmarked and procumbent, but chromosome numbers were not related to forage or seed yield. Also, correlation evidence in one experiment suggested that accessions from lower latitudes tended to be more vigorous and to produce more seed heads than those from higher latitudes. However, the correlation coefficients were quite low and were non-significant in another experiment. The U.S. collection should be expanded to include collections from additional southern locations in the northern hemisphere and the Crimea and Caucasus of the former USSR. All data and seeds have been entered into the USDA Agricultural Research Service’s Germplasm Information Resources Network and are available for general use.