Molecular Diagnosis of ' Sulfur Dioxide Sensitivity Through Genotype Specific Method.

The yeast species is associated with important economic losses due to red wine spoilage. The most common method to prevent and/or control spoilage in winemaking is the addition of sulfur dioxide into must and wine. However, recently, it was reported that some strains could be tolerant to commonly used doses of SO. In this work, response to SO was assessed in order to explore the relationship between SO tolerance and genotype. We selected 145 isolates representative of the genetic diversity of the species, and from different fermentation niches (roughly 70% from grape wine fermentation environment, and 30% from beer, ethanol, tequila, kombucha, etc.). These isolates were grown in media harboring increasing sulfite concentrations, from 0 to 0.6 mg.L of molecular SO. Three behaviors were defined: sensitive strains showed longer lag phase and slower growth rate and/or lower maximum population size in presence of increasing concentrations of SO. Tolerant strains displayed increased lag phase, but maximal growth rate and maximal population size remained unchanged. Finally, resistant strains showed no growth variation whatever the SO concentrations. 36% (52/145) of isolates were resistant or tolerant to sulfite, and up to 43% (46/107) when considering only wine isolates. Moreover, most of the resistant/tolerant strains belonged to two specific genetic groups, allowing the use of microsatellite genotyping to predict the risk of sulfur dioxide resistance/tolerance with high reliability (>90%). Such molecular diagnosis could help the winemakers to adjust antimicrobial techniques and efficient spoilage prevention with minimal intervention.