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Grapevine Phenolic Compounds in Xylem Sap and Tissues Are Significantly Altered During Infection by Xylella fastidiosa

September 2012 , Volume 102 , Number  9
Pages  816 - 826

Christopher M. Wallis and Jianchi Chen

United States Department of Agriculture–Agricultural Research Service, San Joaquin Valley Agricultural Sciences Center, 9611 S. Riverbend Ave., Parlier, CA 93648.

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Accepted for publication 25 May 2012.

Pierce's disease of grapevine (PD), caused by the bacterial pathogen Xylella fastidiosa, remains a serious problem for grape production in California and elsewhere. This research examined induction of phenolic compounds in grapevines (‘Thompson Seedless’) infected with X. fastidiosa over a 6-month period. Two months postinoculation with X. fastidiosa, catechin, digalloylquinic acid, and astringin were found at greater levels in xylem sap; multiple catechins, procyanidins, and stilbenoids were found at greater levels in xylem tissues; and precursors to lignin and condensed tannins were found at greater levels in xylem cell walls. However, such large-scale inductions of phenolic compounds were not observed 4 months after inoculation. Six months after inoculation, infected plants had significantly reduced phenolic levels in xylem sap and tissues when compared with control plants, including lowered levels of lignin and condensed tannins. At 6 months, PD symptoms were severe in infected plants and most photosynthetic tissue was abscised. These results suggest that, even though grapevine hosts may initially respond to X. fastidiosa infections with increased production of phenolic compounds, ultimately, PD causes grapevines to enter a state of decline whereby diseased hosts no longer have the resources to support secondary metabolite production, including defense-associated phenolic compounds.

This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 2012.