The use of markers as surrogates in selection is an attractive alternative to phenotypic selection due to the resources used in accurate estimation of many phenotypes, especially complex ones like yield and quality. The availability of genome wide DNA marker maps for barley has meant that marker assisted selection has become possible for barley but uptake for many complex traits remains limited.

There are a number of reasons for this but the combination of high throughput genotyping based upon functional gene markers and association genetics means that identifying markers linked to genes being manipulated in contemporary elite germplasm is now possible. This approach is the thrust of the Institute led project Association Genetics of Elite UK Barley. The more traditional QTL mapping approaches such as those based upon pair crosses still have a role to play in marker:character association discovery. We are examing the use of combining several pair crosses in a composite population to map characters as we believe this will help facilitate the detection of QTLs that are currently at a low frequency in elite germplasm, having been recently introduced.

For example, the Institute’s micro-satellite marker Bmac0029 is linked within 1cM to a major locus on barley chromosome 3H that affects resistance to Barley Mild and Barley Yellow Mosaic Virus. This marker can distinguish between the rym4 and rym5 resistance alleles which is agronomically important as the former confers resistance to BaYMV-1 and the latter to BaYMV-1 and BaYMV-2. This marker is now in use in many European winter barley breeding programmes where resistance to the disease is a market requirement.

Another Institute developed micro-satellite (Bmac0213) was found to be linked to a gene controlling production of the cyanogenic glycoside Epiheterodendrin. Whilst this marker was partially effective in discriminating between producers and non-producers, it was not reliable enough to be used regularly in MAS. More recently, we identified the causal polymorphism in the gene controlling production of epihetrodendrin, which has enabled us to develop a reliable marker for use in selection. This marker is now available for use by breeders targeting the Scotch whisky market and is being used to identify non-producers as part of the official testing process.

Figure 1: Barley variey markers

Figure 1: Barley variety markers.