An association mapping approach on cell wall digestibility and plant architecture gives insight in yield, persistency and forage quality in perennial ryegrass

Yield, persistency and forage quality are important selection criteria in Lolium perenne, an important forage crop in dairy farming. To gain insight in the genetic control of these complex traits an association mapping (AM) approach was followed. An AM panel of 752 genotypes was assembled using commercial varieties, elite breeding material and natural accessions. Large-scale accurate phenotyping protocols to assess specific aspects of yield, persistency and forage quality were applied. Tillering capacity, leaf elongation rate, heading date, and plant growth were assessed during two consecutive years as traits related to overall yield and persistency. In an additional two-year evaluation, a detailed analysis of traits related to forage quality, such as total dry matter digestibility, cell wall digestibility, cell wall composition and stem/leaf ratio was performed. The AM population shows large phenotypic diversity for the traits investigated and contains a very low level of population structure. For AM, a candidate gene approach, based on targeted resequencing of 539 L. perenne genes putatively involved in cell wall biosynthesis and plant hormone signalling, was followed. A probe capture enrichment procedure followed by NGS, rendered SNPs for association mapping. Significant associations between SNPs and the phenotypes were identified, providing insight into the genetic control of these important selection criteria in Lolium breeding.