Sink Adjustments had Minimal Effects on Carbohydrate Translocation in GRBV Infected Grapevine
Justin Tanner, Dimitrios Mainos, Runze Yu,
Nazareth Torres, Anita Oberholster, and S. Kaan Kurtural*
*University of California Davis, 1 Shields Avenue, Davis, CA,
95616 (skkurtural@ucdavis.edu)
Grapevine red blotch virus (GRBV) impacts winegrape (Vitis vinifera L.) composition and results in economic loss to North American vineyards. GRBV was suspected of impeding carbon translocation within the plant, affecting ripening speed, berry sugar, and flavonoid accumulation. A two-year trial was conducted to investigate the impact and utility of source-sink manipulation on GRBV-infected grapevines to assess whether non-structural carbohydrates would be preferentially translocated to fruit during ripening to mitigate the effects of GRBV. The source:sink ratio was altered by changing the number clusters retained without altering leaf area in a factorial arrangement of uninfected (GRBV [-]) and infected (GRBV [+]) grapevines. Effects of crop level and virus status on leaf and shoot non-structural carbohydrates, plant water status, leaf gas exchange, berry primary and secondary metabolites, and yield components were measured. Total non-structural carbohydrates in leaves began to accumulate around veraison. Conversely, GRBV(-) vines had more total non-structural carbohydrates in shoot sap than GRBV(+) vines. The presence of disease improved plant water status and berry mass. However, must total soluble solids were consistently lower in GRBV(+) vines despite altering the source:sink threefold with cluster removal. Likewise, GRBV(+) plants produced berries with lower anthocyanin content at harvest regardless of crop level in both years. Our results provide fundamental evidence that impeded carbohydrate translocation in GRBV(+) vines is too great to overcome by reducing sink size and will result in inadequate fruit composition regardless of crop level.
Funding Support: USDA-NIFA
