Phytoalexin Stilbenoids of Saperavi and Rkatsiteli(<i>Vitis vinifera L.</i>) as Biomarkers of Resistance to Some Fungal Diseases

Among the biological activities of grape stilbenoids, phytoalexin activity is the most important. The paper deals with a study on the change of phytoalexin stilbenoids response of Saperavi and Rkatsiteli under powdery mildew and gray mold infection in different viticulture areas of Georgia: Mukuzni and Napareuli (for Saperavi), and , Tsarapi and Tibaani (for Rkatsiteli). In July 2024, the grape varieties were infected with a water suspension of powdery mildew. In August 2024, the grape varieties were infected with the conidial water suspension of Botrytis cinerea, and the development of diseases on the grape barries in the period of July-September was observed. In the experimental vineyards trans-resveratrol and its derivatives - glycosides and polymeric stilbenoids in the healthy grape skins of Saperavi and Rkatsiteli were detected. In Saperavi berries skins stilbenoids concentration were higher compared to Rkatsiteli. In both infected varieties the following stilbenoids were identified: trans-resveratrol, trans-ɛ-viniferin, trans-piceid, trans-astringin and cis-piceid. Stilbenoids concentration changes were observed depending on the vine variety and soil-climatic factors. The results represented the stilbenoids as important biomarkers for the Saperavi and Rkatsiteli for resistance against Powdery mildew and Gray mold.