MULTIPLICATION AND MOVEMENT OF XYLELLA-FASTIDIOSA WITHIN GRAPEVINE AND 4 OTHER PLANTS

Xylella fastidiosa, a xylem-limited bacterium that causes Pierce's dis ease of grapevine and other plant diseases, has numerous symptomless h osts. The multiplication and spread of X. fastidiosa within grapevine (Vitis vinifera) and four other reported plant hosts that were preferr ed plants for insect vectors (Himalayan blackberry, Rubus discolor; Ca lifornia mugwort, Artemisia douglasiana; watergrass, Echinochloa crusg alli; and Bermuda grass, Cynodon dactylon) were assessed after vector inoculation. The bacterium was detected by culture and enzyme-linked i mmunosorbent assay. The incubation times required before first detecti on in grape, blackberry, mugwort, and watergrass were 4, 32, 30, and 1 8 days, respectively. The maximum bacterial concentration (CFU per gra m) and percentage of infection in these species were > 10(8) (100%), 1 x 10(7) (58%), 2 x 10(6) (20%), and 4 x 10(5) (31%), respectively. Sy stemic movement of X. fastidiosa distal to the inoculation site was de tected only in grapevine and blackberry. The bacterium was never detec ted in inoculated Bermuda grass. The wide range in the capacities of t hese hosts to support the bacterium's multiplication and spread sugges ts that the epidemiological importance of plant host species for the s pread of Pierce's disease varies greatly.