Unveiling the impact of seasonal weather and fungicide spraying on vineyard autochthonous yeast populations: implications for Riesling wine quality

Abstract

Fungicide spraying is a common viticultural practice that occurs throughout the growth season that protects developing vines and bunches against diseases caused by fungi or oomycetes. The need for fungicide spraying varies seasonally, due to differences in weather conditions, especially rainfall. This study examined the effects of seasonal weather and fungicide spraying on vineyard autochthonous yeast populations and their impact on Riesling wine quality. Biodynamically and conventionally grown Riesling grapes were hand harvested and processed to obtain juice for conducting uninoculated fermentations spanning seasons 2021-2023. In the first two years, differences in fungal diversity between these treatments were mostly found in the juice, favouring the conventional treatment. In 2023, differences in diversity were greater, potentially linked to nutrient leakage from the berries, highlighting the complex interactions between weather conditions and disease management practices as drivers of differences in fungal diversity, challenging our ability to tease apart their individual effects. Regarding the link between yeast populations and volatile aromatic compound production in wine, biodynamic wines were characterised by different terpenes, which suggested the presence of species with glucosidase-activities. However, no direct link can be drawn between yeast community populations and volatile compound production in these fermentations, due to the presence of relic DNA, which distorts the interpretation of results.