A genome wide analysis of key genes controlling diastatic power activity in UK barley (DPGENES)

Abstract

Diastatic Power (DP) is an important quality trait for malt used in adjunct brewing and distilling.  Substantial genetic variation for DP exists within UK elite barley cultivars, but breeding progress has been slow due to the limited demand, compared to the overall barley market, and difficulties in assessing DP. The aim of this project was to develop a suite of genetic markers and robust phenotypic screening methods to identify differences in barley malt diastase activity that can be used by breeders, testing authorities, and maltsters for the early identification and promotion of new varieties for the grain distilling market. To do this, we first identified subsets of barley accessions that contrast for diastase activity using pre-existing data for both spring and winter germplasm. These subsets were the basis for marker development (A) and phenotypic screening protocols (B). 

(A) Twelve high DP and twelve low DP pools of DNA for spring and winter lines were sequenced using a gene enrichment approach, generating over 84,000 polymorphic SNP markers. Using allele frequency differences between low and high DP pools, we identified 66 and 32 SNPs that distinguished between high and low DP in the winters and springs, respectively. For each chromosome region, we chose the marker that showed the highest differentiation between pools, several of these were collocated with known diastase genes, or genes which were annotated with a putative diastase function. Eight KASP marker assays (marker favoured by UK and European breeders) were designed from the SNPs identified from the winters and five for springs. These were tested on a large set of winter and spring germplasm, and a strong correlation (r = 0.92) between genotype and true DP was observed. Further validation was carried out using independent germplasm, supplied by UK and European breeders, which were genotyped, DP predicted and confirmed where possible by micro-malting at Scotch Whisky Research Institute (SWRI).

(B) The subsets selected were sown under a range of conditions expected to differentiate between high and low DP lines.  Winter and spring lines were trialled under both standard and high nitrogen fertiliser treatments, and yield data showed little difference between high and low DP varieties, but in contrast grain nitrogen differed between subsets considerably, at both rates of nitrogen.  Based on these initially findings an improved assessment protocol to complement the markers in an integrated screening package enable breeders to produce new varieties that are specifically targeted at the production of high DP malt.