Gains in dry matter yield and herbage quality from breeding perennial ryegrass

In Western Europe and elsewhere there has been considerable effort during the last 100 years devoted to improving perennial ryegrass (Lolium perenne L.) for agriculture. The first persistent cultivars to be widely used were more digestible than other common pasture species but were no higher yielding than the better wild populations of perennial ryegrass. Two main approaches (here called mainstream breeding and population improvement) have been used to further improve the species, but published information on progress by either means is very limited. In 2006, two plot trials were established at IBERS in the UK to compare the performance of some newer cultivars and candidate varieties with the first persistent cultivars to be widely used in the UK. One trial compared 10 intermediate-heading (6 diplod and 4 tetraploid) cultivars and candidate varieties with the intermediate-heading cv. Talbot, and the other compared 11 late-heading (4 diploid and 7 tetraploid) cultivars and candidate varieties with the late-heading cv. S23. During 2007-2009, one silage cut and six other cuts were harvested each year, dry matter (DM) yields were determined and DM samples analysed for in vitro DM digestibility (DMD), water soluble carbohydrate (WSC) and crude protein (CP) contents. Percentage ground covered by perennial ryegrass in November 2009 was estimated visually. Twenty of the 21 cultivars were significantly (12-38%) higher yielding, 15 were significantly (10- 27 g kg-1) higher in mean DMD, 15 were significantly (25-58 g kg-1) higher in mean WSC and 7 (all diploids) were significantly higher in ground cover in autumn of the third harvest year than either Talbot or S23. There were no significant differences among the varieties in mean CP over all harvests. The newest intermediate-heading cultivar (the diploid Abermagic) produced 29% more DM, was 10 g kg-1 higher in DMD and 51 g kg-1 higher in WSC, and had significantly better ground cover at the end of the third harvest year than Talbot. The newest late-heading cultivar (the tetraploid Aberbite) produced 28% more DM than S23 and was 22 g kg-1 higher in DMD and 58 g kg-1 higher in WSC, although it was similar to S23 in ground cover. Both of these new varieties were developed entirely or partly by population improvement at IBERS over 25 years (1980-2005).