Bhaskar Bondada,* Marc Fuchs, Sadanand Dhekney, Benham Khatabi, Alexander Levin, and Patricia Skinkis
*Washington State University Tri-Cities, 2710 Crimson way, Richland, WA, 99354 (bbondada@wsu.edu)

Grapevine red blotch disease (GRBD), caused by Grapevine red blotch-associated virus (GRBaV), is a severe concern to grapegrowers and winemakers in major grapegrowing regions worldwide. One key aspect of all viruses, including GRBD, is their intimate association with cell components and anomalous structures following infection. This study aimed to analyze symptomatology, vine function, fruit quality, and ultrastructure of various tissues, and to document the relationship of ultrastructural cytopathology with GRBaV infection in Pinot noir, employing multiple microscopy techniques. The infected vines exhibited typical red blotches in leaves, with pinkish-red-colored veins, without rolling off the margins at the onset of ripening. The infected vines developed clusters of hens and chickens and altered seed morphology. Conversely, the healthy seeds were pyriform with a distinct beak. The infection significantly changed the composition of primary and secondary metabolites desired for making wine. Since postveraison berry development and ripening rely on phloem influx, the altered metabolism indicated disruption of the phloem pathway, either in the source leaf or in the berries. Furthermore, the infection modified the browning process, altering periderm formation in infected canes. Nonetheless, the infected green stem turned brown during the cold acclimation process. While the infected vines maintained primary leaf anatomical organization, their chloroplasts underwent significant ultrastructural changes, ranging from complete dismantling to massive accumulation of starch and plastoglobuli development in the chloroplasts and tannins in the cytoplasm. The results demonstrated that structural integrity is vital to maintaining normal metabolism of the grapevine, providing new insights into implementing innovative approaches for GRBD management.

Funding Support: Northwest Center for Small Fruits Research (NCSFR)