Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: 6/6/2005
Publication Date: 7/30/2005
Citation: Cabrera, J., Groves, R.L., Chen, J., Lin, H., Francis, M., Civerolo, E.L. 2005. Seasonal population biology of Xylella fastidiosa genotypes in almond and movement by insect vectors. Phytopatholoy. 95(6):S16.
Technical Abstract: Almond leaf scorch (ALS) disease, caused by the xylem-limited bacterium Xylella fastidiosa(Xf), has been present in the San Joaquin Valley (SJV) since the 1930’s. The disease has re-emerged as a potential threat in many almond producing regions of the SJV. The seasonal fate of Xf populations in ALS-affected almond cultivars was examined monthly at two locations in the SJV in 2004 and 2005. Bacterial populations estimated by isolation on solid media (PW) and QPCR-based assays peaked in early summer and varied significantly between almond cultivars. Two genomic populations of Xf representing both grape and almond genotypes were simultaneously detected in ALS-affected trees. Both Xf genotypes were frequently detected in early season almond samples. Grape genotypes of Xf were more regularly detected during summer and early fall sample dates compared to almond genotypes within the ALS-affected almond cultivar ‘Sonora’. Peak transmission of Xf from symptomatic almond to Catharanthus roseus in laboratory bioassays by green (Draeculacephala minerva) and glassy-winged sharpshooters (Homalodisca coagulata) occurred in early summer. These population studies improve our understanding of the Xf strain composition in ALS-affected trees and a more complete characterization of ALS epidemiology.