Mycobiota of Barbera Grapes from the Piedmont Region from a Single Vintage Year

Abstract

In this study, a description of the fungal populations present on grapes of the Barbera cultivar (Vitis vinifera L.) is reported. Grapes from 15 vineyards in Montferrat, an area located in the Piedmont region in northwest Italy, were sampled at maturation during vintage 2012. The grapes were analyzed by culture-dependent and independent methods. Using plate counts on Wallerstein Laboratory Nutrient agar, we determined a yeast load of about 100 colony forming units (cfu)/mL on the grapes. In total, 206 fungal isolates were identified by two different molecular approaches. Highly reproducible and comparable results were obtained with two identification techniques, that is, PCR-based RFLP analysis of the 5.8S internal transcribed spacer (ITS) rRNA region and PCR–DGGE coupled with sequencing of the 26S rRNA gene, confirming that these two methods reliably identify wine yeasts. Both techniques identified a mycobiota mainly composed of Aureobasidium pullulans (73% of the isolates), followed by Rhodotorula glutinis (12%), Hanseniaspora spp. (8%), Issatchenkia terricola (5%), Torulaspora delbrueckii (1%), and Cryptococcus carnescens (1%). Moreover, PCR–DGGE based on DNA and RNA extracted directly from grapes confirmed the presence of A. pullulans, H. uvarum, and Starmerella bacillaris (synonym Candida zemplinina).