Yeast strains used in beer making arose through numerous mixing events, Forbes reports.
Researchers led by the Pacific Northwest Research Institute's Aimée Dudley sequenced the genomes of nearly four dozen yeast strains used in brewing and baking along with 65 other strains, and compared them to 430 other yeast strains with publicly available genomes. As they report in PLOS Biology, they uncovered 13 different populations, four of which included most of the beer-related strains. Two of those four represented yeast used to make ales, one used to make lagers, and one group was used to make both beer and bread.
The researchers developed an admixture graph and used other analyses to determine the origins of those four beer yeast strains. Dudley and her colleagues found that the beer yeast strains were largely polyploid admixtures of yeast populations related to European grape wine strains and Asian rice wine strains.
This, the researchers note, suggests that these beer yeast populations may have arise through East-West transfer of fermentation technology, possibly along the Silk Road.