Study of grape microorganisms in Moldovan vineyards: influence of human and natural factors

Abstract

The objective of this study was to investigate the microbial diversity on the grape berries under different climate conditions. Sixteen samples from ten vineyards were taken from three PGI regions in Republic of Moldova Moldova during years 2018–2020. The year of harvest had a significant effect on the amount of yeasts, but the geographical location did not significantly influence this criterion. As natural factors, the influence of temperature and precipitation during both the growing season and the month of grape harvest was studied. The selected methods for vineyard plant protection were as follows: fungicides to control powdery mildew, fungicides to control mange and insecticides. The total yeast population per grape ranged from 3.8E+04 to 2.3E+07 CFU/berry and the culturable yeast population ranged from 1.7E+03 to 8.0E+06. The harvest month temperature affects the yeast population the most, fungicide use in mealybug control reduces the culturable yeast population but increases the total yeast population; insecticide treatment only increases the total yeast population but has no impact on culturable yeasts.In addition, six species yeast have been identified: A.pullulans, M.pulcherrima, H. uvarum, R. Glutinmis, R. graminis and S.cerevisiae. The Saccharomyces cerevisiae strain isolated from the 2020 crop is totally different from the 2018 and 2019 crops. The bacteria population is at a low level, except for a few samples, P. damnosus, L. brevis, L.fermentum, G. oxydants were isolated.