The consociation with sage (Salvia officinalis) reduces the susceptibility of grapevine leaves to Plasmopara viticola

Introduction Volatile organic compounds (VOCs) play a crucial role in plant communication and defence, with aromatic plants representing an important and promising natural source of these compounds. In this study, we evaluated the role of sage VOCs in enhancing grapevine defence against Plasmopara viticola under both controlled and field conditions. Methods Sage and grapevine were consociated in an airtight box system for 24 or 48 h, after which grapevine leaves were inoculated with P. viticola . In a three-year field trial, sage was intercropped with grapevine along two strips of vine rows spaced 50 m apart to avoid VOC cross-contamination. During each growing season, leaves were repeatedly collected from consociated and non-consociated areas of the vineyard and artificially inoculated with P. viticola in Petri dishes. In selected assays, sage leaves were attached to the lids of the Petri dishes to evaluate a possible incremental effect of sage VOCs. Results and Discussion Overall, sage VOCs reduced grapevine susceptibility to downy mildew by 35.8 to 52.2% under all experimental conditions, suggesting that they may act as resistance inducers. Moreover, consociation with sage significantly altered the volatilome within the airtight boxes, with the VOC profile of the consociated system closely resembling that of sage alone, resulting in significantly lower disease severity in inoculated grapevine leaves. The further reduction in disease severity (by 26.1 to 59.0%) observed when sage leaves were present during the inoculation assay suggests a possible, direct inhibitory effect of sage VOCs on P. viticola infection. These findings highlight the potential of sage VOCs as a natural tool for enhancing grapevine defence against downy mildew. Further long-term studies are required to confirm our exploratory field observations, elucidate mechanisms for sage VOC efficacy against P. viticola , and assess its agronomic and economic sustainability within an agroecological framework.