Just read through this and wanted to give some insight into the idea of terroir with regards to yeast.
In 2009, two high profile papers in the journal Nature published global genome data on the yeast species Saccharomyces cerevisiae. This gave interesting insight into whether or not trait variations in S. cerevisiae are due to population structure (ie lineage) or source environment (ie terroir). A 2011 PLOS Genetics paper titled “Trait Variation in Yeast is Defined by Population History” concluded that trait variation (trait variation leads to different flavors) is largely defined by which lineage the strain belongs to vs. the source environment that the yeast was isolated. Up until 2012, there were five known lineages of the yeast S. cerevisiae: European, Sake, Malaysian, North American, and West African. A yeast belonging to the European lineage does not mean that it was isolated in Europe. It just means that genetically it groups into the lineage that was declared European by the researchers that proposed these concepts years ago (same is true for the other lineages). In fact, most of the brewing, distilling, and winemaking strains that are used in the western world today, including America, are from the European lineage. Even more, yeast from this lineage have been isolated in China. How yeast from the same lineage can be isolated in such varying areas is still a topic of debate, but human activity such as trade and travel is one proposed reason.
The point being, most yeast that are used in Kentucky, Scotland, America, etc. are proposed to be of the same lineage – European. So, it’s not so much that Kentucky and Tennessee have the perfect environments to harbor whiskey-making yeast. The data seems to show, as Sherman pointed out, that as colonist moved from Europe to New England and then down into Kentucky and Tennessee, they brought with them (unknowingly or knowingly) yeast capable of fermenting a grain mash. Therefore, as people moved west, the same would be true – they took with them yeast from the European lineage. And this idea seems very plausible when you consider the fact that most wild yeast isolated from California vineyards are of the European lineage. In fact, the standard S. cerevisiae lab strain (S. cerevisiae is a model organism for research…it was the first sequenced eukaryotic organism) was originally isolated from a fig in a California vineyard, and is of the European lineage.
As a side note, all of the strains discovered so far that group within the North American lineage can’t metabolize maltose. If the yeast can’t metabolize maltose, it fails as a suitable beer or whiskey yeast.
Currently, we are sequencing the necessary genomic regions of our proprietary yeast – isolated from a Texas ranch – to determine which lineage it groups.
Finally, while a strain’s lineage may be the principal driving factor for trait variation, data from a 2011 paper in PLOS One shows that strains of the same lineage can form sub-groups with metabolic discrimination based on the different ecological niches they inhabit (ie oak tree vs. vineyard grape; distillery vs. brewery).
In other words, lineage is most influential in determining trait variation within S. cerevisiae. However, the ecological niche that the strain inhabited (or had recently inhabited) when it was captured will also affect trait variation, just to a lesser degree.