Marker-Trait Associations for Flavonoids and Biomass in White Clover (Trifolium repens L.)

Abstract

White clover, a primary forage legume in temperate permanent pasture, is limited by poor adaptation to abiotic stress factors such as water scarcity. Flavonoids contribute to abiotic stress tolerance in plants. Genetic analysis of flavonoid accumulation may help in understanding its relationship to plant growth and morphology in white clover. The objective of this research was to discover marker-trait associations for biochemical and morphological traits previously identified as associated with drought tolerance, using clonally replicated white clover plants. Parents and 131 progeny of a bi-parental cross between the cultivar ‘Grasslands Kopu II’ (K2) and the ecotype ‘Tienshan’ (T) were genotyped with 104 microsatellite (SSR) markers and a Diversity Array Technology (DArT) assay, revealing 320 polymorphisms segregating from parent K2 and 208 from parent T. Markers on linkage group (LG) 1–2 were significantly (p < 0.005) associated with concentrations of the flavonols quercetin (Q) and kaempferol (K) and the Q:K ratio (QKR). A cluster of linked markers including prs406 accounted for 21 %, 167 % and 53 % change in Q, K, and QKR trait values, respectively. Polymorphic loci on LGs 6–1 and 7–1 in parent K2 influenced shoot and root dry matter. Loci on LGs 7–2 and 8–1 influenced root dry matter but not shoot dry matter. Root to shoot ratio was influenced by loci associated with markers from parent T on LGs 4–1 and 8–1. These results support a hypothesis that flavonoid metabolism is under close genetic control and largely independent of genetic factors influencing growth, suggesting that it might be possible to improve both abiotic stress tolerance and growth potential in white clover. These marker-trait associations revealed deleterious alleles in an elite cultivar, and indicate the potential value of diversity from wild germplasm for white clover improvement.