Grape maturity significantly influences yeast community on grape berries: basidiomycetous yeasts are dominant colonizers of immature grape berries in northwestern Iran

Grape maturity is one of the factors that influences the species diversity of yeasts on grapes. While several studies have been carried out on the species diversity of yeasts on mature grape berries in different grapevine producing countries, there is a paucity of data on the biodiversity of yeasts on immature grape berries worldwide, including Iran. This study was conducted to identify the species diversity of epiphytic and endophytic yeasts on immature grape berries in five selected vine growing regions in northwest Iran. 59 grape samples were collected during early stage of grape berry ripening. The percentage of isolation was 35.5% and 117 yeast isolates were recovered as epiphytes; while, no yeast was isolated as endophyte. Identity of yeast isolates by M13 fingerprinting marker and sequence data of D1/D2 region of 28S rDNA revealed a rich diversity of epiphytic yeast species on immature grape berries, with basidiomycetous yeasts being dominant, whereas ascomycetous yeasts were mostly isolated on mature grape berries in our previous studies. Fifteen yeast species were identified among those, Naganishia uzbekistanensis and N. adeliensis were the predominant. Aureobasidium pullulans was also found on immature grape berries with high frequency. Comparing the locality of the sampling areas, the highest biodiversity index was calculated for the Urmia and Lahrud regions. The grape cultivar was an additional factor shaping the biodiversity. This is the first report of Candida peoriensis and Starmerella graminicola as inhabitants of grape berries and C. peoriensis, S. bacillaris and Vishniacozyma foliicola are new for the mycobiota of Iran.