Dissemination of oenological yeasts through bird migration in Sicily.

Abstract

The composition of yeast communities on shown to be dependent on several factors, including geographical location of the vineyard, type of soil, age of the vineyard, grapevine variety and harvesting technique. Moreover, insects and birds were in part responsible for the dissemination of fermentative yeasts during their feeding (Francesca et al, 2009). In order to evaluate the dissemination of fermenting yeasts, migrating and vineyard inhabiting birds were caught and ringed in four experimental sites: “Riserva Naturale Integrale Lago Preola e Ghorghi Tondi” (Mazara del Vallo, TP) and the Sicilian islands of Lampedusa, Ustica and Linosa. The last sites represent important stop-over for migrating birds. A total of 344 birds, belonging to different species, were captured and their mouths and cloacae were plugged with sterile cotton swabs and streaked onto malt extract agar for yeast isolation. A total of 125 yeast isolates were clustered into five groups based on colony appearance onto Wallerstein Laboratory (WL) nutrient agar (Pallman et al, 2001), while seven groups were recognized by optical microscopic observation. Yeast identification was preliminary carried out by amplification of ITS-5.8S rRNA region (Esteve-Zarzoso et al, 1999) and, subsequently, by D1/D2 region of the 26S rRNA gene sequencing. Metschnikovia pulcherrima, Candida stellata, Pichia guilliermondii, Hanseniaspora uvarum, Torulaspora globosa, Torulaspora delbrueckii, Zygosaccharomyces bailii and Saccharomyces cerevisiae were found. Furthermore, the study was focused on the nine strains of Saccharomyces cerevisiae isolated. They were characterized for technological traits with interest in wine production such as hydrogen sulphide production, ethanol and potassium metabisulphide resistance. Strains showing the best performances were used to carry out sterile must micro-fermentations to select yeast starter cultures. To our knowledge, this research showed a new finding regarding the ecology of vineyards: for the first time it has been proved that Saccharomyces cerevisiae strains can be disseminated by sedentary and migrating birds. Among them some strains with oenological potential were found.