Assessment of genetic diversity in cultivars of white clover (Trifolium repensL.) detected by SSR polymorphisms

Abstract

White clover (Trifolium repens L.) is an important temperate pasture legume that plays a key role as a companion to grass species, such as perennial ryegrass (Lolium perenne L.). Due to the outbreeding nature of white clover, cultivars are highly heterogeneous. Genetic diversity was assessed using 16 elite cultivars from Europe, North and South America, Australia, and New Zealand. Fifteen simple sequence repeat markers that detect single, codominant polymorphic genetic loci were selected for the study. The genetic relationships among individuals were compared using phenetic clustering, and those among cultivars were compared using nonmetric multidimensional scaling. Intrapopula tion variability exceeded interpopulation variability, with substantial overlap among populations and weak interpopula tion differentiation. No obvious or significant differentiation was observed on the basis of morphology or geographic origin of the cultivars. The number of parental genotypes used to derive each cultivar was not a major determinant of genome-wide genetic diversity. The outcomes of this assessment of genetic variation in elite white clover germplasm pools have important implications for the feasibility of molecular marker-based cultivar discrimination, and will be used to assist the design of linkage disequilibrium mapping strategies for marker-trait association.

Molecular characterisation and interpretation of genetic diversity within globally distributed germplasm collections of tall fescue (Festuca arundinacea Schreb.) and meadow fescue (F. pratensis Huds.)

“…As individual alleles are unable to be conWdently attributed to a speciWc sub-genome within the polyploid samples, alleles from all samples were scored in a dominant manner and converted into a binary (presence/absence) matrix. The polymorphism information content of each SSR marker was calculated as a measure of heterozygosity (Nei 1973) within each locus and was calculated as described by George et al (2006).…”

Genetic diversity of Aquilegia (Ranunculaceae) species and cultivars assessed by AFLPs

“…Information on genetic variation in Aquilegia germplasm could also be used to assist genetic mapping, quantitative trait locus (QTL) studies and the design of linkage disequilibrium mapping strategies for marker-trait association (George et al, 2006). Diversity at marker loci is currently the most feasible strategy for characterizing diversity in wild and cultivated germplasm.…”

Identification of homologous, homoeologous and paralogous sequence variants in an outbreeding allopolyploid species based on comparison with progenitor taxa

“…White clover is an obligate outbreeding allotetraploid forage legume (2n = 4x = 32) exhibiting high levels of intrapopulation genetic diversity (George et al 2006b) and intragenotype heterozygosity (Kölliker et al 2001;Jones et al 2003). Although inbred lines based on self-fertile mutants have been developed by single seed descent (Michaelson-Yeates et al 1997) high levels of residual heterozygosity were observed (Jones et al 2003).…”