Forage Improvement via Marker-Assisted Selection

Abstract

The use of DNA markers to accelerate genetic improvement of forages presents a unique set of opportunities, challenges, and benefits. Our experiments in full-sib mapping populations of white clover and perennial ryegrass have detected >75 quantitative trait loci (QTLs), each with multiple marker:trait associations at specific locations in either the perennial ryegrass or white clover genome. A subset of these QTL are robust (detected in multiple years / sites / populations) and exert a substantial influence on performance, warranting exploration of development for application in Marker-assisted Selection (MAS) breeding programmes. Ryegrass QTLs associated with herbage yield, seed yield, plant size and habit, cold tolerance, seasonal regrowth, and disease have been identified, whereas QTL discovery in white clover has been focused on reproductive traits. Markers from two white clover QTLs were used to develop marker assays suitable for selection of parental plants with superior breeding value for seed yield potential. Tandem testing of the two assays over two field seasons and eight populations indicates that substantial change in seed yield may be achieved (up to 90% increase), and that the marker / allele / phase relationships to plant performance are population specific. These data point to an opportunity to develop selection tools on a population specific basis, and to a challenge to implement MAS approaches tailored for open-pollinated population breeding systems.