Postharvest UV-B radiation as a sustainable strategy for controlling Botrytis cinerea and associated microbiota in wine grapes

Abstract

Damaged grapes and grey mould are major causes of reduced oenological quality, with Botrytis cinerea being particularly relevant because of its sanitary and technological impact. This study evaluated, for the first time, the effect of postharvest UV-B radiation on the surface microbiota of Tempranillo and Garnacha Blanca grapes. Healthy grapes and grapes with more than 35 % B. cinerea infection were treated with UV-B doses of 0.18 or 1.40 GJ m^–2. Trials were conducted over three vintages (2022–2024) in experimental vineyards in La Rioja. Total microbial load, moulds and B. cinerea viability were assessed by plate counts and PMA-qPCR. UV-B significantly reduced microbial populations, depending on dose, cultivar and health status. The highest dose was the most effective, decreasing moulds by up to 1 log unit and markedly reducing B. cinerea viability, particularly in infected grapes. Garnacha Blanca responded more strongly than Tempranillo, possibly because of structural differences in berry skin. Although effects were more variable in healthy grapes, viable microorganisms declined consistently in most treatments. Postharvest UV-B therefore exerts a direct antimicrobial effect and represents a sustainable, non-chemical option for improving grape sanitary quality, reducing fungicide use and supporting oenological quality.

Acknowledgements

This work is part of project PID2023-150695NB-I00, funded by MCIU/AEI/10.13039/501100011033/ERDF, EU.