Genetic diversity for cell wall digestibility in a diverse Lolium perenne collection

The digestibility of the cell wall has a significant impact on the fodder quality in Lolium. This is especially the case at reproductive maturity, when the lignification of the cell wall and the proportion of stems increase. The relevance of this factor becomes clear if we take into consideration that a 1 % increase of the digestibility of the fodder improves the daily intake per cow by 0.2 kg and results in an increase of the daily milk production of 0.4 kg per cow (Gilliland, Quality Counts on Northern Irish Recommended List, 2007). Detailed information on the variability available for cell wall digestibility in individual ryegrass genotypes and how it differs for different organs is currently not available. This information could, however, be exploited to breed ryegrasses with a higher feeding value. In a preliminary study we identified significant differences in the cell wall digestibility of the leaf fraction of ten Lolium perenne genotypes. The glucose release varied between 2.58 and 3.89 g glucose/20 g dry biomass. Significant differences for glucose release were identified between leaf and stem samples. To get a better estimation of the variability available for cell wall digestibility in L. perenne, a subset of 30 genotypes selected within a broader collection of 300 genotypes from current varieties were analyzed in detail. Preliminary results indicated that improving total digestibility might be achieved through enhanced cell wall digestibility in stems. However more genotypes should be analysed before firm conclusions can be drawn.