Prospects For Genomic Selection In Forage Plant Species

Genomic selection (GS) is a powerful new method for exploitation of DNA sequence polymorphisms in selective breeding of animals and plants, through prediction of breeding values based on all markers distributed genome-wide. Forage grasses and legumes are good target species for GS, as many traits of importance are difficult or expensive to measure, and are measured late in the breeding cycle.  Biological factors that vary across the range of candidate species, including reproductive mode and polyploid genomes, are both challenges and opportunities for GS.  Two strategies for implementing GS will be described for a representative species group (ryegrasses).  The first strategy requires relatively little modification of current schemes, but could lead to significant reductions of operating cost.  The second scheme would allow two rounds of selection for key agronomic traits within a time-period previously required for a single round, potentially  leading to doubling of the rate of genetic gain.  However the second scheme requires a purpose-designed reference population.  In both schemes, the limited extent of linkage disequilibrium (LD), which is the major challenge for GS implementation in ryegrass breeding, is addressed.