# Relationships Among Origin, Genotype, and Oenological Traits of _Brettanomyces_ Yeasts
## 3 Discussion  
The yeast _Brettanomyces_ is a good example of an organism facing human-driven selection pressures, where the broad genetic and phenotypic diversity makes its study extremely important to overcome their spoilage effect. Population genomic studies have revealed the coexistence of auto- and allotriploidization events with different evolutionary outcomes [28]. A wide investigation of the genotypic survey of _B. bruxellensis_ using microsatellite analysis found that the population is structured according to ploidy level, substrate of isolation, and geographical origin of the strains [29]. They found that clustering was correlated to variable stress response, and the geographical origin has a different contribution to the population structure, strongly suggesting an anthropic influence on the spatial biodiversity of this microorganism. In this study, these results were confirmed. Indeed, the analysis of the _Brettanomyces_ population also using a multiparametric evaluation showed the relation between the origin of isolation and genotype profiles of strains with the most relevant oenological traits. However, specific phenotypic traits are insufficiently investigated considering the great genomic diversity of these yeast species. The influence in these relations is different among these parameters. Some oenological parameters, such as theoretical ethanol and volatile acidity, played a minor role in the discrimination of the biotypes, while the parameters fermentation rate (Tuscany1, cluster 1) and ethyl phenols production (Guese beer, cluster 1 and 2) played a greater role in the relationship with origin and phenotype groups. In this regard, we found that fermentation rate and ethyl phenols production showed a significant and negative correlation that could be of interest to understand the adaptation of these yeasts in hostile environments where the dominance of the ecological niche is related to the production of ethyl phenols. The production of volatile phenols by _B. bruxellensis_ strains is variable and has been extensively described in oenological conditions [8; 23; 25; 27; 30; 31; 32; 33]. Most studies involved end-point analyses, which makes it difficult to distinguish between the intrinsic capacities of the strains and their modulation by external parameters. Furthermore, the respective importance of the different factors governing such variability is poorly described; a few authors showed that volatile phenols' production was both strain-dependent and wine matrix-dependent [34; 35; 36; 37]. The abiotic characteristics of isolation environmental habitat could also play a role as well as brewing strains, characterized by a more efficient metabolism toward ferulic acid (leading to 4-EG) than p-coumaric acid compared to wine isolates [38]. Some wine and soft drink isolates possess a duplication of the vinyl phenol reductase gene, which is absent in beer isolates [24]. However, while all these studies confirmed the existence of intraspecific variation, their impact on the production of volatile phenols and their possible ecological significance remains to be properly assessed. The conversion of hydroxcinnamic acids (HCAs) into volatile phenols may have an important impact from an ecological viewpoint; HCAs have antimicrobial properties, and the ability to convert HACs into less toxic compounds could promote yeast growth [39]. The significant and negative correlation between fermentation rate and ethyl phenols production may confirm this role. Indeed, some environmental _Brettanomyces_ strains (Cameroon strains) showed high fermentation rates and low ethyl phenols production. However, further data and insights are needed to clarify this behavior. Regarding the genetic variability, a high genetic diversity of _B. bruxellensis_ isolates from wine environments was found [35]. On the other hand, each specific genotype could be isolated repeatedly in the same winery over decades, demonstrating an unsuspected persistence ability.