Biological control of Pierce’s disease of grape caused by Xylella fastidiosa achieved by various strategies leading to pathogen confusion
S. LINDOW (1) (1) University of California, Berkeley, U.S.A.

Xylella fastidiosa, vectored by xylem-feeding insects, moves between xylem vessels after inoculation, inciting water stress symptoms in grape.  Because of the incompatibility of traits enabling virulence to plants and insect transmission the pathogen modulates gene expression by accumulating a quorum sensing molecule that partitions its population between those non-adhesive cells that colonize plants, and adhesive cells that colonize insects. The production of extracellular enzymes and active motility is suppressed while the production of surface adhesins increases with as cell density, thereby increasing the local concentration of DSF, a family of unsaturated fatty acids that mediate quorum sensing. Disease control can be achieved by artificially increasing DSF levels in the plant, leading to high adhesiveness of the pathogen, thereby limiting its ability to move and grow in the plant after inoculation. Transgenic grape plants expressing rpfF, encoding the DSF synthase in X. fastidiosa exhibit high resistance to Pierce’s disease both in greenhouse and field studies. Burkholderia phytofirmans PsJN can multiply and move extensively within grape and produces a small molecule in culture that induces high levels of adhesiveness and thus hyper-biofilm formation in X. fastidiosa. The growth and movement of X. fastidiosa in grape and symptom development is dramatically reduced in plants inoculated with B. phytofirmans either before or after that of the pathogen.

Abstract Number: P3-2
Session Type: Plenary