Association genetics of UK elite barley (AGOUEB)

Abstract

Our aim was to DNA fingerprint 1,000 barley genotypes using a panel of 3,000 molecular markers to characterise the variation that exists amongst UK elite barley varieties and associate variation in marker profiles i.e. DNA fingerprints with differences in performance and morphological characters. Over 500 of these lines had been evaluated in spring and winter barley National and Recommended List trials between 1988 and 2006 and thus an extensive body of performance data (yield, height, disease resistance, quality etc.) already existed for these lines. Additionally we grew a subset of lines representing market successes and failures over our survey period in a series of trials to provide an unambiguous estimate of breeding progress and additional data to improve the prediction of means of varieties that generally were not grown in the same trials.

Multi-variate analysis of the marker data generated by the DNA fingerprinting resulted in three general groupings that represented spring barley, two row winter barley and six row winter barley. Whilst some varieties were genetically (and morphologically) quite similar, e.g. Angora and Melanie, there were still considerable genetic differences between varieties within the three major groupings and therefore plenty of genetic variation for breeders to continue to exploit. This was borne out by the results of the trials carried out within the project, where we clearly demonstrated breeding progress for yield, which appeared to be due to increased grain size, in the winter and spring crop and also for malt extract in the spring crop.

We have also been able to identify associations of individual molecular markers with morphological characters used to establish Distinctness, Uniformity and Stability (DUS) in National List testing. For the first time, we can therefore confirm that DUS characters are controlled by genes on each of barley’s seven chromosomes. We have also been able to closely define the chromosomal region harbouring these controlling genes and use the similarity between barley and the fully sequenced genomes of rice and Brachypodium to identify potential candidate genes for the characters. The success of this approach has been demonstrated by the cloning of the major gene responsible for the development of anthocyanin pigmentation in various barley tissues. The approach is also proving successful in identifying genes responsible for performance characters such as yield. Whilst this offers the prospect of utilising DNA markers to predict the favourable combinations of alleles as a short-cut to directly measuring performance, a technique known as Marker-Assisted Selection, we still need to determine how all these genes act together to produce enhanced performance.

Finally, the extent of the DNA fingerprinting that we have carried out means that future experiments can be based upon the same material that we have studied but could access the existing molecular marker information, removing the need and expense of large-scale genotyping material in the experiment as well as phenotyping.