Objective: In the present work, the changes suffered by plants at the level of secondary metabolism were studied, in terms of the amount of trans-resveratrol synthesized as a specific phytoalexin induced, when infection by Grapevine leafroll virus occurs vine plants. All from the 2018-2019 harvest, from a commercial cultivar located in the province of San Juan, Argentina

Methods: Extracts from leaves of grapevine plants infected with various vid viruses were made and subjected to HPLC-MS analysis to evaluate the content of trans-resveratrol as a specific induced phytoalexin. Plants in which the leaf extracts had a negative viral titer were used as a negative reference, and HPLC grade trans-resveratrol was used as a standard for the analytical method.

Results: Four plants infected with V. vinifera L. cv were detected. Thompson Seedless, one infected only with GLRaV-3, another infected with GLRaV-3 coinfected with and GLRaV-2, a third plant infected with GLRaV-2 coinfected with GLRaV-3 and GVA, and finally a plant that did not show viral titer (used as negative control). Leaf extracts from infected plants showed an increase of more than 200% of resveratrol compared to the extract from the plant used as a negative control (healthy plants).

Conclusion: Vitis vinifera L. cv Thompson Seedless plants infected with GLRaV viruses alone, or a combination of these with other specific vine viruses, synthesize resveratrol, which demonstrates that this compound, a product of secondary metabolism, acts as a specific phytoalexin induced in response to viral infection.