Forest Oak Woodlands and Fruit Tree Soils Are Reservoirs of Wine-Related Yeast Species

Abstract

A large-scale sampling plan was performed over four years in three different vineyards to evaluate the occurrence of wine-related yeast species in the soils underneath both vines and forest oak and fruit trees close to the vineyards. Ascomycetous fermentative yeasts were present in 27% of 320 soil samples throughout the sampling years, with incidences that could not be related to sampling season. The greatest percentages of occurrence were found in soils under fig (76%), apple (73%), and oak (41 to 55%) trees. Soils were less contaminated under vines (6%), while these yeasts were not recovered from soil underneath chestnut trees. Other soils showed intermediate percentages of occurrence. A total of 139 fermentative ascomycetes were identified from 25 species. Ninety-six isolates came from 21 different non-Saccharomyces species and 43 isolates from four Saccharomyces species. Soils underneath fruit trees had 11 different species. The most common isolates belonged to Lachancea thermotolerans and Torulaspora delbrueckii, while Sacharomyces paradoxus predominated in the soil underneath oak trees. Saccharomyces cerevisiae was found at low frequency (7% of total isolates) during all sampling years under fruit trees, but it was not recovered from vineyard or oak tree soils. The wine spoilage species Zygosaccharomyces bailii was recovered in only one sample of vineyard soil. For a given soil system, the species recovered varied strongly over the years, suggesting the existence of complex yeast communities. In particular, soils in the vicinity of vineyards were natural reservoirs for yeast species of enological interest.