Figure 1.

Map showing the regions of Europe relevant for the emergence and distribution of S. pastorianus. The regions shown should be understood in their historical context. Bavaria denotes the original duchy/electorate between the Alps, the Danube, the Salzach, and the Lech. Franconia comprises the territories in the northwest of Bavaria, bound by the Danube to the south and the low mountain range (Frankenwald) to the north. The Upper Palatinate comprises the region between the Böhmerwald (low mountain range Bohemian Forest), the Danube and the low mountain ranges (Fichtelgebirge). Bohemia describes the former kingdom with its capital, Prague. Top-fermentation was the primary brewing method in most of Europe, including Bohemia, but bottom-fermentation became common in the 14th century in Franconia and the Upper Palatinate. Once the Beer Purity Law (Reinheitsgebot) was introduced in 1516, bottom-fermentation became universal in Bavaria, with few exceptions. One exception was Schwarzach, which had a famous wheat-beer brewery. Brewing of this beer transferred to the Munich Hofbräuhaus in 1602. Top-fermenting yeast from Einbeck also came to the Hofbräuhaus in 1615. The hypothesis put forward in this paper is that one of these events introduced the S. cerevisiae parent of S. pastorianus to the Munich Hofbräuhaus. Here, it hybridized with the S. eubayanus that was already used there as part of the bottom-fermenting ‘Stellhefen’ (pitching yeast) mix. From the early 19th century, yeasts from the Munich Spaten brewery (Spaten owner Sedlmayer previously worked at Hofbräuhaus) were widely distributed, including to the Carlsberg brewery in 1845. Copenhagen and Berlin became the major centres for the cultivation of pure S. pastorianus from Bavarian bottom-fermenting Stellhefen and Grimma (home of the Froberg Brewery) and Saaz (home of the Bürgerliches Brauhaus) are key locations that are also described in this text and in Table 6.