Transgenic grapevine rootstock clones expressing the coat protein or movement protein genes of Grapevine fanleaf virus:: Characterization and reaction to virus infection upon protoplast electroporation

The reaction to Grapevine fanleaf virus (GFLV) infection in 42 independent transgenic grapevine rootstock 41B clones expressing the coat protein (CP) or movement protein (MP) gene of GFLV was assayed by protoplast electroporation. Two of the 26 transgenic clones expressing the CP gene did not support the accumulation of GFLV MP to detectable levels, 12 accumulated substantially lower levels of MP, and 12 accumulated equivalent levels of MP relative to protoplasts of nontransformed controls at 72 h post-electroporation, as shown by Western blots with anti-MP gamma-globulins. Interestingly, inhibition of MP accumulation was achieved against virions but not viral RNAs, and was dependent on the inoculum dose. No interference was observed with the multiplication of Arabis mosaic virus, which is closely related to GFLV, likely due to low nucleotide identity between the CP genes. Also, one of the 16 transgenic clones expressing the MP gene significantly reduced the accumulation level of GFLV CP at 72 h post-electroporation, as shown by DAS-ELISA with anti-GFLV gamma-globulins. The potential of protoplast electroporation as rapid identification of GFLV-resistant grapevine clones at the cell level will be discussed relative to field screening for resistance at the plant level by nematode-mediated GFLV transmission. (c) 2005 Elsevier Ireland Ltd. All rights reserved.