Identification of QTL Associated with Morphological and Agronomic Traits in White Clover (Trifolium repens L.).

White clover (Trifolium repens L.) is an important cool-season perennial forage legume species used in pastures to improve forage quality.  The identification of molecular markers linked to morphological and agronomic traits could facilitate the development of superior white clover cultivars.  The objectives of this study were to map quantitative trait loci (QTL) associated with morphological and agronomic traits using a F₁ population from a double pseudo-testcross between two highly heterozygous genotypes derived from Durana (GA02-56) and SRVR (GA02-15). Phenotypic data was collected from multiple field locations and years for morphological traits (leaf length and width, petiole length, stolon diameter and inter-node length), and for growth traits (plant spreading, plant height, and stolon number). Analysis of variance indicated there were significant effects from location, replicates within location, genotype, and genotype x location for all traits evaluated.  Correlation coefficients indicated that field growth traits were highly correlated with each other. Broad sense heritability estimates for all traits evaluated were less than 25%.  The population was genotyped with 343 simple sequence repeat (SSR) markers and multiple QTL model (MQM) analysis was used to identify 37 QTLs on eight linkage groups associated with five morphological traits and four plant growth traits. The consistent location of QTL for the same traits or highly correlated traits across different locations and years indicates the potential value of utilizing marker-assisted breeding for white clover improvement.