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.

The impact of a forage plant breeder – the story of Herrick Sydney (Syd) Easton (1946 - 2023)

“…During the 1990s the use of DNA markers, linked to genes, was researched as means of improving the efficiency of selection in applied plant breeding. By the 2000s Syd, along with other forage plant breeders, was keen to explore the application of marker assisted selection (MAS) (Barrett et al 2001;Faville et al 2003;Barrett et al 2006) and was involved in work to discover markers linked to herbage production Journal of New Zealand Grasslands 85: 7-16 (2023) related traits (Sartie et al 2011;Faville et al 2012), root distribution (Faville et al 2006;Crush et al 2006;Crush et al 2007) and seed production (Sartie et al 2006(Sartie et al , 2018. Future objectives, direction and requirements for forage plant breeding to continue to support pastoral farming was thoroughly reviewed and concluded that "future grass breeding, aided by MAS and genetic modification of both plants and endophytes, will place strong emphasis on feeding value for optimal animal performances, especially in intensive systems" (Williams et al 2007).…”

Prospects for Trifolium Improvement Through Germplasm Characterisation and Pre-breeding in New Zealand and Beyond

“…The history and successful development of GWAS techniques have been well documented ( Ikegawa, 2012 ; Visscher et al, 2017 ). GWAS have been successful in identifying novel variant-trait associations ( Tam et al, 2019 ; Jones et al, 2020 ) and allowed marker-assisted selection breeding programmes in forages to be developed ( Hayward et al, 1994 ; Barrett et al, 2001 , 2006 , 2009 ; Dolstra et al, 2007 ; Roldán-Ruiz and Kölliker, 2010 ; Riday, 2011 ). However, the number of GWAS studies in forages compared to other crops is low.…”