Genomic Selection in Forage Breeding: Accuracy and Methods

ABSTRACT The main benefits expected from genomic selection in forage grasses and legumes are to increase selection accuracy, reduce cycle time, and potentially reduce evaluation costs per genotype. Aiming at designing a training population and first generation of selection, deterministic equations were used to compare the gain and accuracy of six genomic selection methods implemented within the context of traditional experimental plot designs used in forage breeding. Combined use of both phenotypic and genotypic information was superior to other methods using low density markers (approximately three per cM) and for heritability lower than 0.6 but resulted in lower selection gain per year in relation to individual genomic selection using higher marker density. Initial accuracies were increased by a selection index method proposed as a procedure to improve long‐term rates of gain for advanced generations using genomic selection. Application of genomic selection methods to forage breeding is expected to be of greatest value under the following circumstances: (i) when phenotypic evaluation of individual plants is incapable of predicting performance under sward conditions, (ii) when it is difficult or impossible to apply meaningful selection pressure within families, or (iii) when time‐intensive phenotypic evaluations necessitate long cycle times, for example, 4 to 5 yr.