Submitted to: American Phytopathological Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 8/1/2006
Publication Date: 8/1/2006
Citation: Uyemoto, J.K., Rowhani, A. 2006. New and emerging viral diseases in grapevines grown in california. American Phytopathological Society Abstracts.
Interpretive Summary: Up to circa 1985, the predominant rootstock AXR#1 began to fail due to a new strain of the grape phylloxera, an insect pest of grape roots. Then, as the California wine grape industry shifted to phylloxera-resistance rootstocks, a myriad of new problems arose. Young grape plants developed poor stands, produced red or yellow canopies (leaf color dependent on fruit color), and plant death. In our investigations, we determined that viruses were present and represented one component of the disease complex. We then examined these hybrid rootstocks as potential indicators of new grape viruses. In a series of trials where scores of field collections were inoculated onto various combinations of hybrid rootstocks, several lethal graft-transmissible agents (LGTAs) were found. One LGTA, a variant of Grapevine leafroll associated virus 2 (GLRaV-2), was first discovered in Redglobe (RG) table grape and designated as GLRaV-2RG. It killed grafted plants on five rootstocks: 3309C, 1616C, 1103P, 5BB, and 5C and was latent on another 13 rootstocks. In contrast, the type strain of GLRaV-2 was not lethal on the same rootstocks. Work is in progress to moleculary characterize the remaining LGTAs.
Technical Abstract: Due to a new strain of grape phylloxera, Daktulosphaira vitifoliae, the hybrid rootstock AXR#1, of choice for more than 30 years in California's wine vineyards, began to fail; circa 1985. The industry then turned to other hybrid rootstocks resistant to the new phylloxera strain. However, some hybrid rootstocks (of varied Vitis speciation) expressed incompatibility symptoms and plant death when grafted with certain scion sources. We examined the use of hybrid rootstocks as potential indicators of new grape viruses and the differential host responses on these rootstocks detected several lethal graft-transmissible agents (LGTAs). One LGTA, identified as a variant of Grapevine leafroll associated virus 2 (GLRaV-2), was first discovered in Redglobe table grape and designated GLRaV-2RG. This variant does not cause leafroll in Cabernet franc or Cabernet Sauvignon, standard indicators, but is lethal on 3309C, 1616C, 1103P, 5BB, and 5C, and latent on another 13 rootstocks. The type strain of GLRaV-2 was not lethal on the same rootstocks. Based on responses in several trials, five additional sources with different LGTAs were found. The characterization of these unknowns is underway.