Saccharomyces cerevisiae biodiversity in spontaneous commercial fermentations of grape musts with 'adequate' and 'inadequate' assimilable-nitrogen content.

Aim: To evaluate whether intraspecific diversity of Saccharomyces cerevisiae in wine fermentations is affected by initial assimilable-nitrogen content.
Methods and Results: Saccharomyces cerevisiae isolates from two spontaneous commercial wine fermentations started with adequate and inadequate nitrogen amounts were characterized by mitochondrial DNA restriction analysis. Several strains occurred in each fermentation, two strains, but not the same ones, being predominant at frequencies of about 30%. No significant differences were detected by comparing the biodiversity indices of the two fermentations. Cluster analysis demonstrated that the strain distribution was independent of nitrogen content, the two pairs of closely related dominant strains grouping into clusters at low similarity.
Conclusions: The genetic variability of S. cerevisiae in wine fermentations seemed not to depend on the nitrogen availability in must.
Significance and Impact of the Study: Nitrogen content did not affect the genetic diversity but may have induced a 'selection effect' on S. cerevisiae strains dominating wine fermentations, with possible consequences on wine properties.