Meristem tip culturing for the elimination grapevine viruses
Young grapevines have been successfully propagated from virus infected grapes. Ten different virus isolates have been included in- these experiments. We have found that it is easy to culture plants from explants which are 2-3 mm in size or larger. Although we have cultured plants from explants which are l mm or smaller, the survival rate is low. We hope to improve that survival rate by further refinement of technique. Early data using the ELISA test on the plants which are out of tissue culture and in soil indicate that a significant number of explants have been freed of virus. This is very encouraging data which suggest that the meristem tip culture is successful for virus elimination. However, retesting over the next few years as the vines mature is needed to be sure that the virus is completely eliminated from the plants, not just in low concentrations. A large number of explants have been sucsessfully cultured and transferrsd to soil in the 1991-1992 funding year but due to staff and funding shortages they have not been ELISA tested. Grapevine virus collections essential to further studies of virus elimination techniques have been established and are thriving. Experiments are underway to determine the optimum explant size for grapes infected with leafroll, fanleaf, Rupestris stem pitting and corky bark. The progress which has been made in developing antisera for leafroll and corky bark should facilitate this work. In addition, efforts are being made to use antiviral chemotherapeutics as a step in the tissue culture process. Wood from four leafroll-infected cabernet sauvignon selections from Napa Valley has been collected and the selections are undergoing therapy; these materials will be used for evaluations of the effectiveness of the therapy and for subsequent evaluation of the effects of the virus diseases on clonal characteristics.