Submitted to: CDFA Pierce's Disease Control Program Research Symposium
Publication Type: Abstract Only
Publication Acceptance Date: 12/1/2013
Publication Date: 12/16/2013
Citation: Wallis, C.M., Wallingford, A.K., Chen, J. 2013. Rootstock effects on progression of Pierce's disease symptom development and possible mechanisms. In: Proceedings of the Pierce's Disease Research Symposium, December 16-18, 2013, Sacramento, California. p. 214.
Technical Abstract: Rootstocks are utilized to reduce incidence and severity of root-associated diseases. However, the ability of rootstocks to limit progression of stem-afflicting diseases has not been studied extensively. Rootstocks potentially could slow progression of scion-afflicting diseases such as Pierce’s disease (PD), which is caused by Xylella fastidiosa (Xf). In this experiment, greenhouse-grown Chardonnay or Cabernet Sauvignon grapevines were grafted to a variety of different rootstocks and infected with Xf. PD symptoms and Xf titers were assessed six months later. Chardonnay grafted to Freedom or Salt Creek (Ramsey) rootstocks had reduced disease severity compared to Chardonnay grafted to RS-3 or Schwarzmann. Cabernet Sauvignon grafted to 1103 Paulsen, 101-14 Millardet et de Grasset, 3916, 420A, or Schwarzmann had reduced PD severity compared to 110 Richter, 5BB Kober, or SO4. Chardonnay grafted to RS-3 had greater Xf titer than Chardonnay grafted to 101-14 Millardet et de Grasset, Freedom, or Salt Creek. No other significant differences in Xf titers were observed. Although reductions in disease severity were not always consistent between cultivars (Schwarzmann), certain rootstocks were considered promising for reduced PD symptom progression (101-14 Millardet et de Grasset and Salt Creek). To observe the potential mechanism for reduced symptom development, phenolic compounds were analyzed within scion xylem sap. However, with the exception of caftaric acid (greater levels in rootstocks with fewer PD symptoms) and quinic acid (positively associated with PD symptoms), no consistent relationships between constitutive or induced phenolic levels and PD symptoms were found. Field studies would be necessary to observe whether or not rootstocks can consistently slow development of Pierce’s disease.