Molecular Characterization of Cell Wall Digestibility in Lolium : An Association Mapping Approach

Forage quality and biomass yield are among the most important selection criteria in forage grass breeding. We are currently studying the genetic diversity for cell wall digestibility available in perennial ryegrass (Lolium perenne), a major forage species in temperate dairy agriculture. We assembled an association mapping (AM) population of 600 genotypes composed of commercial varieties, elite breeding material and natural accessions, with a very low level of population structure. Well-defined phenotyping protocols that consider developmental timing (vegetative versus generative) and effects of plant morphology (e.g. leaf to stem ratio) have been applied. Phenotyping for cell wall digestibility and related biochemical parameters has now been completed for one growing season. Here we describe patterns of population structure in the AM population using SSR and SNP markers. A transcriptome database containing SNP diversity information for 14 genotypes and phylogenetic analysis (Ruttink et al., 2012) of the Cinnamoyl CoA Reductase (CCR)  gene family have been used to identify SNPs in five L. perenne bona fide CCR orthologs. Patterns of allelic diversity and linkage disequilibrium decay for Cinnamoyl CoA Reductase (CCR) genes have been determined in the AM population. Future work will focus on phenotypic analysis for a second growing season and SNP analysis of other candidate genes for cell wall digestibility.

Reference

Ruttink et al. (2012). Development of a SNP identification pipeline for highly heterozygous crops. In : Barth, S. & Milbourne, D. (Eds.) Breeding strategies for sustainable forage and turf grass improvement, pp 131-140, Springer Netherlands.