Abstract
China has a large barley germplasm collection which has not been well characterized and is therefore underutilized. The Bmy1 locus encoding the β-amylase enzyme on chromosome 4H has been well characterized in the worldwide barley germplasm collections due to its importance in the malting and brewing industry. The Bmy1 locus was chosen as an indicator to understand genetic potential for improvement of malting quality in Chinese landraces and Tibetan wild barley. The genetic diversity of 91 barley accessions was assessed using allele specific Multiplex-ready molecular markers. Eight accessions were further sequenced, based on the Multiplex-ready marker diversity for Bmy1 in the germplasm. Six of the eight accessions clustered together in a unique group, and showed similarities to ‘Haruna Nijo’, wild barley accession PI296896 and ‘Ashqelon’. Sequence comparisons with the known Bmy1 alleles identified not only the existing 13 amino acid substitutions, but also a new substitution positioned at A387T from a Chinese landrace W127, which has the highest β-amylase activity. Two new alleles/haplotypes namely Bmy1-Sd1c and Bmy1-Sd5 were designated based on different amino acid combinations. We identified new amino acid combination of C115, D165, V233, S347 and V430 in the germplasm. The broad variation in both β-amylase activity and amino acid composition provides novel alleles for the improvement of malting quality for different brewing styles, which indicates the high potential value of the Chinese landraces and Tibetan wild barley.
Highlights
A significant high value use of barley is for malting to produce malt as a raw material for brewing beer and producing whiskey
Amino acid comparisons of the Bmy1 gene in W127 and Ashqelon revealed that both accessions had a composition of C115, D165, V233, S347 and V430 which distinguished it from Haruna Nijo at 115
The current study demonstrated that the Chinese landraces and Tibetan wild barley were close to wild barleys, in support of Tibet as a centre of diversity for barley germplasm [10]
Summary
A significant high value use of barley is for malting to produce malt as a raw material for brewing beer and producing whiskey. Based on the European Brewing Convention, malting quality is determined by more than 30 traits/parameters [1]. A major process of malting and brewing is to convert starch into fermentable sugars. Four major enzymes are involved in this process, including a-amylase (a-1,4-glucan glucanohydrolase; EC 3.2.1.1), b-amylase (a-1,4-glucan maltohydrolase; EC 3.2.1.2), limit dextrinase (a-dextrin 6-glucanohydrolase; EC 3.2.1.142) and a-glucosidase (a -D-Glucoside glucohydrolase; EC 3.2.1.20) [2]. Depending on mashing and brewing processes, the requirement for DP can vary from low to moderate to very high. Starch adjuncts are used to brew beer in Asia and North America, a high to very high DP is required to degrade the extra starch. When full malt or liquid sugars are used to produce beers in Europe and Australia, lower or moderate levels of DP are preferred. New genetic variation for malting quality has always been a target for brewers and breeders
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