MECHANISMS OF PIERCES DISEASE TRANSMISSION IN GRAPEVINES: THE XYLEM PATHWAYS AND MOVEMENT OF XYLELLA FASTIDIOSA. XYLEM STRUCTURE AND CONNECTIVITY IN GRAPEVINE SHOOTS SUGGESTS A PASSIVE MECHANISM FOR THE SYSTEMIC SPREAD OF BACTERIA IN GRAPE PLANTS IN

• Author(s): Matthews, Mark; Rost, Thomas; Chatelet, David;
• Abstract: Grapevine xylem is composed of vessels connected by intervessel bordered pits with pit membranes that prevent the passive movement of particles, especially at the stem-leaf junction where most vessels end. The traditional view of Xylella fastidiosa (Xf) movement within the xylem requires the digestion of the intervessel pit membrane to move from one vessel to another. However, bacteria such as Yersinia enterocolitica (Ye) and fluorescent beads have been observed moving rapidly within the grapevine xylem, suggesting a pathway for passive movement. In this report, we used air and latex paint to confirm the existence a xylem vessel pathway from stems into the leaf lamina. Anatomical investigation of the leaf xylem revealed a switch from vessels to tracheids at about 50-60% the length of the leaf lamina. In addition, inoculations of gfp-Xf showed that bacteria never reached the leaf margin where the symptoms appear, suggesting that tracheids inhibited the free movement of Xf.
• Publication Date: Dec 2005
• Journal: 2005 Pierce's Disease Research Symposium