Browsing IJAFR volume 50, no. 1, 2011 (Special Issue) by Subject "Breeding"
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Gains in dry matter yield and herbage quality from breeding perennial ryegrassDuring the last 100 years, in Western Europe and elsewhere, considerable effort has been 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 for the UK, but no recent experiments to assess progress have been published. In 2006, two plot trials were established at IBERS 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 involved comparing 10 intermediate-heading (6 diploid and 4 tetraploid) cultivars and candidate varieties with the intermediate-heading cv. Talbot, and the other involved comparing 11 late-heading (4 diploid and 7 tetraploid) cultivars and candidate varieties with the late-heading cv. S23. During 2007 to 2009, one silage cut and 6 other cuts were harvested each year, annual dry matter (DM) yields were determined and DM samples analysed for in vitro DM digestibility (DMD), water soluble carbohydrate (WSC) and crude protein (CP) concentrations in the DM. Percentage ground covered by perennial ryegrass in November 2009 was estimated visually. Twenty of the 21 cultivars were significantly (12 to 38%) higher yielding, 15 were significantly (10 to 27 g/kg) higher in mean DMD, 15 were significantly (25 to 58 g/kg) higher in mean WSC and 7 (all diploids) were significantly higher in ground cover in autumn of the third harvest year than their respective control cultivars. 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 higher in DMD and 51 g/kg 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 tetra-ploid Aberbite) produced 28% more DM than S23 and was 22 g/kg higher in DMD and 58g/kg higher in WSC, although it was similar to S23 for ground cover at the end of the third harvest year. Both of these new varieties were developed entirely or partly by population improvement at IBERS over 26 years (1980 to 2005). These results suggest that the rates of gain in DM yield under nitrogen-limiting conditions and in herbage WSC concentration from perennial ryegrass breeding can be improved by utilizing new technologies and better breeding strategies.
Ryegrass breeding - balancing trait prioritiesIn all ryegrass breeding programmes it is necessary to select a range of traits within different cultivar types, varying in ploidy and flowering time. The traits selected in ryegrass breeding can be broadly grouped into production traits such as yield, quality and persistency; those seed production traits crucial for delivery of the cultivar, as well as those traits that can benefit the environment, or allow ryegrass to be used for biofuel production. The emphasis placed on each trait will depend on its economic value within the various farming systems where each cultivar will ultimately be used, as well as the potential to make genetic gain in each trait. In all cases multiple trait selection will be required, to develop a cultivar improved for key traits of interest but importantly the cultivar must not have unacceptable performance for any trait. Where the genetic variation is inadequate within perennial ryegrass it may be necessary to enhance ryegrass diversity. In the future this could be achieved through targeted introgression from the closely related Festuca species, or through introduction of genes via genetic modification. Funding of ryegrass breeding internationally will increasingly be subject to the economic success of a few larger seed companies as Government funding for field-based breeding is diminishing and shifting focus to more basic research, often of a molecular nature. Ensuring this expensive basic research and associated molecular technologies are used effectively in ryegrass breeding programmes will remain a challenge when seed companies operating field-based programmes are vulnerable to considerable economic pressure.