QTL analysis of components of nitrogen use efficiency in a perennial ryegrass mapping family under high and low nitrate supply in flowing solution culture.

Breeding forage crops capable of using fertiliser and soil N more efficiently offers a clean technology route to increased sustainability of livestock production, via lowering recommended fertilizer rates, reducing the agricultural footprint with respect to pollution and reducing the wider consumption of non-renewable resources. Nitrate and ammonium are not only the predominant forms of mineral N available in most soils, but are likely to continue to be major forms of N fertiliser applied to temperate grassland, given the gaseous emissions cost associated with a switch to urea. To identify and incorporate new genes associated with nitrogen use efficiency in forage grasses (Lolium perenne), we have designed a programme of research that makes use of genetic mapping and marker assisted selection approaches. A mapping population has been developed that segregates for nitrogen uptake and nitrogen utilisation efficiencies. By phenotyping this population under highly controlled optimal and limiting regimes of N supply in flowing solution culture, a number of genomic regions mapping to linkage groups 1, 2, 5 and 7 have been identified that segregates with nitrogen uptake and utilisation efficiencies. This population also segregates for a number of other desirable agronomic traits including flowering time, growth and regrowth after cutting, and forage quality traits such as water soluble carbohydrate content, dry matter digestibility, and concentration of poly unsaturated fatty acid (PUFA) in the forage. An additional advantage of this population stems from the fact it has been developed in the genetic background of an elite agronomic cultivar. This presentation will examine the QTLs that have been identified so far using this population and how they are being bread into elite varieties for simultaneous improvement of multiple traits.