Genetic Variation of RAPD Markers for North American White Clover Collections and Cultivars

Abstract

New white clover (Trifolium repens L.) cultivars with improved winter hardiness and persistence are needed for pasture-based cropping systems in temperate regions of North America. This study evaluated, quantified, and compared genetic variation of populations developed from five recently collected germplasms from Georgia (GA), Iowa (IA), Pennsylvania (PA), West Virginia (WV), and Prince Edward Island (PEI), Canada, and three improved cultivars (‘Regal’, ‘Sacramento’, and ‘Will’). ‘Aurora’ alsike clover (T. hybridum L.) was included for comparison. Random amplified polymorphic DNA (RAPD) profiles of these populations were compared. Euclidean metric distance matrices were calculated for all possible pairwise combinations and were evaluated by analysis of molecular variance (AMOVA). An interpopulation distance matrix [Φst, an analog of F as described by Excoffier et al. (1992)] for the nine populations was used to calculate a dendrogram based on the unweighted paired group method of arithmetic averages. As anticipated, alsike clover was separated from white clover. At a higher level of similarity, the white clovers were separated into only two groups. One group consisted of GA, IA, PA, and PEI germplasms collected from long-established pastures. The second group included Regal, Sacramento, and Will cultivars and the WV collection. Although Will was originally derived from pasture collections, it has a larger leaf size than any of the five white clover collections. The surprising genetic similarities of eight populations derived from different climates and geographic regions of the continent may indicate a common European origin for much of the naturalized white clover in North American pastures.