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Title: PCR screening for Xylella fastidiosa in grape genebank accessions collected in the Southeast US.

Author
item Stover, Eddie
item RIAZ, S. - UNIVERSITY OF CALIFORNIA
item WALKER, M.A. - UNIVERSITY OF CALIFORNIA

Submitted to: American Journal of Enology and Viticulture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/13/2008
Publication Date: 12/1/2008
Citation: Stover, E.W., Riaz, S., Walker, M. 2008. Pcr screening for xylella fastidiosa in grape genebank accessions collected in the Southeast US. American Journal of Enology and Viticulture.59:437-439.

Interpretive Summary: The National Clonal Germplasm Repository (NCGR) in Davis, CA maintains the US collection of warm climate grapes in a field genebank in Winters, CA. This collection includes numerous accessions which are highly susceptible to the important grape disease know as Pierce’s Disease (PD) as well as many PD-tolerant grapes which are native to the SE US. If glassy winged sharpshooter, the main vector for PD, became established near the genebank, then if the PD causal agent, Xylella fastidiosa (Xf), is already in the genebank would permit the rapid spread of Xf throughout the grape collection. Therefore, DNA screening for Xf was conducted using a test which is broadly effective with all Xf strains which have been tested. Basal leaf tissue was collected from 60 different grape varieties in the genebank representing a broad cross section of grape types collected where PD is normally widespread and different periods of time since the grapes were collected. Only the ‘Chardonnay’ checks which were inoculated with PD were found to be positive. It appears that NCGR genebank grape varieties collected as budwood in the southeastern US, where Xf and PD are endemic, are not a significant source of Xf. There appears to be no reason for removing these vines if GWSS populations become established in the area surrounding the genebank.

Technical Abstract: The National Clonal Germplasm Repository (NCGR) in Davis, CA maintains the US collection of warm climate grapes in a field genebank in Winters, CA. This collection includes numerous accessions which are highly susceptible to Pierce’s Disease (PD) as well as many PD-tolerant accessions which are native to the SE US. If glassy winged sharpshooter became established in the Winters area, then reservoirs of the PD causal agent, Xylella fastidiosa (Xf), within the collection would provide abundant inoculum for the rapid spread of Xf throughout the genebank. Therefore, PCR screening for Xf was conducted using a primer pair that is genome sequence specific to Xf and is reported to provide a high degree of sensitivity and specificity to all Xf strains which have been tested. Basal leaf petioles were collected from 60 different accessions in the NCGR representing a broad cross section of taxa and periods of time since collection in the region where Xf is endemic. Only ‘Chardonnay’ previously inoculated was found positive for presence of Xf. It is concluded that NCGR grape accessions collected as budwood in the southeastern US, where Xf and PD are endemic, are not a significant reservoir of Xf. There appears to be no reason for removing these vines if GWSS populations become established in the area surrounding the genebank.