MAGNETIC RESONANCE IMAGING: A NONDESTRUCTIVE APPROACH FOR DETECTION OF XYLEM BLOCKAGES IN XYLELLA FASTIDIOSA-INFECTED GRAPEVINES

• Author(s): Labavitch, John; Shackel, Ken; Greve, Carl; Matthews, Mark; Perez, Alonso; Walton, Jeffrey;
• Abstract: Results from Pierces disease (PD) research programs led by Matthews, Rost and Labavitch (reported in 2001, 2002 and 2003 in San Diego) have provided substantial support for the idea that obstructions in the vine's water-transporting xylem tissue develop rapidly post-inoculation, before an appreciable bacterial population has been established. The results also strongly suggest that these obstructions, and likely other aspects of the PD "syndrome", result from the grapevine's active responses to the presence of X. fastidiosa (Xf), rather than to direct "action" by the bacterium. Thus, careful analysis of the timing of changes in xylem element anatomy and function relative to Xf introduction, as well as to external symptoms of disease development, is important for establishing reliable indicators of the "stage" of PD development. The analyses done thus far have been based on destructive tissue sampling. Such sampling can be particularly blind when it is done on vines in which (based on our earlier results) internal symptoms of PD are present but external, visible symptoms are not yet present. In the report of the year 1 work of our study (Shackel and Labavitch, 2003), the success of Mr. Prez and Dr. Walton in imaging non-functional vessels in the stems of PD-infected and ethylene-treated grapevine stems was demonstrated. In this report we elaborate on those studies, showing that locations of reduced vine water transport capacity, as determined by nondestructive MRI analysis, is correlated with the locations of PD and ethylene effects on vessel functionality (destructive analysis). In addition, because interpretation of the meaning of the MRIs with respect to the anatomy and functioning of vessels is a crucial aspect of our work, we have described the methodology used to validate our approach to obtaining the relevant information from the MRIs.
• Publication Date: Dec 2004
• Journal: 2004 Pierce's Disease Research Symposium