Persistency and genomic tools in forage grasses

Abstract

Perennial ryegrass (PRG; Lolium perenne) is the most widely cultivated forage grass species in Ireland. Despite its widespread use, there have been meagre gains in the improvement of agronomically important traits, including persistency. Persistency in the context of forage breeding, refers to the expected performance of a sward over time. Novel breeding techniques such as hybridisation and genomic approaches have the potential to advance the understanding of persistency as well contribute to the improvement of the trait. The Lolium and Festuca genera are attractive candidates for hybridisation due to their complementary characteristics in the context of forage production and environmental challenges. Lolium exhibits greater digestibility and Festuca possesses superior resilience to abiotic stress. To establish the extent of the representation of these characteristics in different Festulolium hybrids, a five year field experiment was undertaken in a mild Atlantic climate. Overall, Festulolium hybrids performed at a very similar level as Lolium species in terms of persistency, yield and ensilibility. The development of molecular markers in perennial ryegrass breeding has the potential to accelerate the genetic gain in many economically important traits, particularly in persistency. A reduced representation assay was deployed in a number of PRG populations with varying levels of complexity. This assay performed comparably to approaches with a much greater number of SNPs. However, some aspects of the PRG genome, including repetitive regions, as well as the incomplete nature of PRG genomic resources likely led to technical challenges in the deployment of this assay. An alternative reduced representation genotyping approach was implemented (SeqSNP), to investigate if competition and selective pressures present in the field have the potential to affect the survival, and persistency, of individual plants in the sward. Some shifts in the pooled genetic profiles of the swards were observed, when compared to the original seed, however these changes were sporadic and no clear trends or relationships were observed. In summary, reduced representation assays efficiently and adequately captured genetic diversity in PRG pooled populations. Swards of mixed cultivars exhibit little proportional changes over a two year period.