AVF Proj. ID: 619
Year Funded: 2015
Category: Pest-Disease - Red Blotch
Investigators: Marc Fuchs, Keith Perry and Deborah Golino

Biology and Spread of Grapevine Red Blotch-Associated Virus

Summary:


 

Grapevine red blotch-associated virus (GRBaV) was isolated from table and wine grapes, as well as rootstocks, affected by red blotch, a recently recognized viral disease in grapevines.  Analysis of the genetic diversity among isolates of GRBaV indicates the existence of two groups (clades) of genetic variants (Krenz et al., 2014, Al Rwahnih et al., 2015).  Producing a full-length infectious clone of a representative isolate of each of the two clades showed systemic GRBaV infection of healthy grapevines following agroinoculation and the manifestation of typical disease symptoms, i.e. interveinal reddening on Vitis vinifera cvs. Cabernet franc, Cabernet Sauvignon, Syrah, Pinot noir and Pinot gris; and chlorotic and necrotic leaf areas on Vitis vinifera cv. Chardonnay, while infection was latent in rootstock genotype 3309C.  This work revealed that GRBaV isolates of both clades cause red blotch disease. Analysis of the spatio­temporal incidence of GRBaV in a selected vineyard of Cabernet franc in California and in New York was consistent with the occurrence of virus spread in the former but not in the latter vineyard.  GRBaV isolates spreading in California corresponded to phylogenetic clade 2.  A survey of alternate hosts in proximity to the diseased vineyard in California showed some free-living grapevines infected with GRBaV, suggesting the existence of a hemipteran vector. Insect sticky traps placed in the section of the California vineyard with extensive clustering of diseased vines in 2014 and 2015 revealed a diversity of insect families, genera and species that visited the vineyard, among which, the majority of specimens of three species consistently tested positive for GRBaV in PCR.  These species are investigated for their potential to transmit GRBaV in controlled conditions in the greenhouse.

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