The effect of pyrimethanil on the growth of wine yeasts.

Aims: The toxicity of the fungicide pyrimethanil on the growth of wine yeasts was evaluated using in vivo and in vitro experimentation.
Methods and Results: The effect of pyrimethanil in the must was studied during the spontaneous wine fermentation of three consecutive vintages and by the cultivation of Hanseniaspora uvarum and Saccharomyces cerevisiae yeasts in a liquid medium. The residues of the fungicide were measured using gas chromatography-mass spectrometry system and the sugar concentration in the must using HPLC-RI. Molecular and standard methods were used for identifying the yeast species. Although the pyrimethanil residues in grapes were below the maximum residue limits, they significantly affected the reduced utilization of sugars in the first days of fermentation. Its residues controlled the growth of H. uvarum during the fermentation and during in vitro cultivation as well.
Conclusions: The fungicide pyrimethanil had an effect on the course and successful conclusion of spontaneous wine fermentation that was correlated with the initial concentration of yeasts in the must.
Significance and Impact of the Study: The impact of pyrimethanil on the indigenous mixed yeast flora in fermenting must was investigated for the first time. The results showed that its residues might play an important role in the growth and succession of yeast during spontaneous wine fermentation.