Traditional Norwegian Kveik Yeast: An Ancient Sister Group to DomesticatedSaccharomyces cerevisiae

Abstract

AbstractKveik is the common name of yeast that has been used in traditional farmhouse brewing of western Norway for generations. Its fast fermentation, increased flocculation, temperature tolerance, and rich flavor profile have led to growing interest in recent years. Previous genetic analyses have shown that kveik forms a distinct group within theSaccharomyces cerevisiaetree and placed its origins within the Beer I clade of industrial brewing yeasts, although with signs of mixed ancestry.In this study, we revisited the phylogenetic position of kveik within theS. cerevisiaetree. We searched for traditional farm breweries in western Norway and collected ten samples of potential kveik yeast.Using Illumina whole genome shotgun sequencing, we reconstructed the phylogenetic tree of kveik based onde novogenome assemblies and variant calls of our new kveik samples, along with published wild and domesticatedS. cerevisiaestrains. We calibrated and used sequential computational experiments at different thresholds to determine the most probable phylogenetic position of kveik yeast.Previously sequenced kveik genotypes form a clade with our new samples clustering partially by place of origin. Our results indicate that kveik is indeed a compact clade withinS. cerevisiaewith significantly reduced polymorphism compared to common brewing yeasts and wild strains. Contrary to what was previously thought, our analyses support a more ancient divergence of kveik and place it closer to the root of theS. cerevisiaetree.In conclusion, our genetic analyses suggest that kveik is a unique and ancient yeast group, distinct from other domesticatedS. cerevisiaestrains. Considering a possible far east origin of kveik yeast, the apparent endemism to western Norway remains as a big paradox These findings have important implications for the understanding of yeast domestication and the use of kveik in modern brewing practices.