Effects of rootstock on Xylella fastidiosa infection and grapevine sap phenolics
A. K. Wallingford (1), C. M. Wallis (1), J. CHEN (1). (1) USDA ARS, Parlier, CA, U.S.A.
Pierce’s disease, caused by the bacterium <i>Xylella fastidiosa</i>, poses a threat to grape production in the United States and warm climates elsewhere. There are numerous grapevine rootstocks available that may impart increased vigor or tolerance to soil-borne pests. However, little is known about the potential of rootstocks to provide increased resistance to pathogens that infect scions. In this study, host biochemical responses to <i>X. fastidiosa</i> infection were compared between potted Chardonnay vines grown on 101-14 MG, 110R, RS3, and Salt Creek, as well as Cabernet Sauvignon vines grown on 101-MG and 110R. Plants were sampled three- and six-months after <i>X. fastidiosa</i> inoculation, with bacterial titers determined by qPCR and phenolics quantified by high-performance liquid chromatography. Pierce’s disease symptoms were rated at six months. We observed differences due to rootstocks in bacterial titers and symptom development, as well as associated changes in many phenolic compounds. To examine the effects of rootstocks on the production of constitutive and induced phenolic compounds, root vigor also was calculated by weighing root balls at the end of the experiment. Root vigor was then correlated with phenolic production in both non-infected and <i>X. fastidiosa</i>-infected plants. These results improve understanding of the role that different rootstocks play in imparting resistance to xylem-limited bacterial pathogens.
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