Do Totiviruses of the veil of Flor yeasts provide an evolutionary advantage?

Abstract

The main objective of this work was to isolate and characterize viruses that infect both Saccharomyces and other Flor veil-forming genera and suggest the possible consequences they can have on the processes of formation of the Flor veil of typical D.O. Jerez-Xèrés-Sherry wines. Results obtained show that different Flor veil yeast strains isolated in Fino wines and in Amontillados presented a great resistance to ethanol and all of them presented infection by Totiviruses. These were identified after the extraction of double-stranded RNA and amplified by multiplex PCR with specific primers for the most common viruses involved in the killer factor. Subsequently, the same strains of both the S. cerevisiae species and Wickerhamomyces anomalus were subjected to an antiviral treatment with ribavirin. After microbiological analysis with Methylene Blue (MB) plates and by rt-PCR, it was determined that most of them did not show killer factor and the viruses involved in it had been correctly eliminated under the treatment with ribavirin. Subsequently, competition and implantation experiments of the treated and untreated yeasts were carried out against their controls. The wines inoculated with yeasts infected by Totiviruses showed to be dominant in all cases.