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. Estimates of DP (taken from recommended and national list trials between 1994 and 2012) from a collection of UK elite winter and spring varieties were used to identify contrasting sets of high and low DP varieties. DNA samples were pooled within sets and exome capture sequencing performed. Allele frequency estimates of Single Nucleotide Polymorphisms (SNPs) identified from the sequencing were used to identify genomic locations associated with differences in DP. Individual genotypes were generated from a set of custom KASP assays, both within sets and in a wider germplasm collection, to validate allele frequency estimates and marker associations with DP. QTL identified regions previously linked to variation in DP as well as novel associations. QTL colocalised with a number of genes annotated as having a diastase related function. Results indicate that winter barley is more genetically diverse for genes influencing DP. The marker assays produced by this work represent a resource that is available for immediate use by barley breeders in the production of new high DP varieties.
Highlights
One of the most economically significant uses of barley (Hordeum vulgare L.) worldwide is in the production of alcohol following malting, with about 20% of annual barley production being used for processing (FAOSTAT: http://www.fao.org), the vast majority of which is used by maltsters
Sets of 12 lines each for winter and spring contrasting sets were selected based on the combined estimate of Diastatic Power (DP) from both historical estimates and the means taken from the processability project. 9k iSelect genotypes were used to avoid selecting highly genetically similar varieties
The results presented here demonstrate the effectiveness of using allele frequency estimates from pooled NGS data from phenotypically contrasting sets to map quantitative traits, allowing the use of extremely high marker density along with maximum phenotypic diversity
Summary
One of the most economically significant uses of barley (Hordeum vulgare L.) worldwide is in the production of alcohol following malting, with about 20% of annual barley production being used for processing (FAOSTAT: http://www.fao.org), the vast majority of which is used by maltsters. The Scotch Whisky Association ceased producing annual production figures for grain whisky after 2012 but the data up to that date can be used to estimate that the amount of wheat used doubled from around 500,000 t in 1980 to just under 1 million t in 2008 This means that the demand for high diastase malt in the UK is around 100,000 t, assuming an inclusion rate of 10%. Allowing for malting losses and the different moisture contents of unmalted and malted barley, this equates to malting purchases in the order of 115,000 t at 85% dry matter This represents a significant market, and breeding opportunities exist for new varieties that combine the high agronomic performance associated with modern varieties with high levels of diastase activity. The development of molecular markers that are tightly linked to genes responsible for variation in DP would provide an opportunity for breeders to incorporate this trait into their selection programmes in a cost effective manner
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