Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: 3/13/2007
Publication Date: 6/1/2007
Citation: Sisterson, M.S., Thammiraju, S.R., Daane, K., Groves, R.L. 2007. Alfalfa as an important inoculum source of Xylella fastidiosa [abstract]. Phytopathology. 97:S108.
Technical Abstract: Pierce’s disease of grapes and almond leaf scorch disease are chronic problems in the San Joaquin Valley of California. Both diseases are caused by the bacterium Xylella fastidiosa, however limited information exists to characterize the primary inoculum sources for acquisition by insect vectors. We evaluated the potential of alfalfa forage crops to serve as primary X. fastidiosa inoculum sources by: 1) testing the relative susceptibility of 14 cultivars of alfalfa to systemic infection by X. fastidiosa via needle inoculation, 2) monitoring the seasonal incidence of X. fastidiosa in 8 alfalfa fields, and 3) documenting the seasonal abundance of vectors that are abundant in this crop. Needle inoculations successfully resulted in systemic infections in all cultivars examined. The incidence of X. fastidiosa at field sites varied from 0 to 35% across sites and sampling dates. Vector abundance varied by collection date and field site and the only known insect vector collected during our studies was the green sharpshooter, Draeculacephala Minerva. Results from this project will aid in determining the relative importance of alfalfa as an epidemiologically inoculum sources of X. fastidiosa.