GENE SILENCING AS A STRATEGY TO INDUCE GRAPEVINE FANLEAF VIRUS (GFLV) RESISTANCE IN GRAPEVINE ROOTSTOCKS

Viral infections in grapevines cause physiological disorders that lead to foliar deformations, alterations in the berry color and finally reductions in productivity. Most viral infections in grapevine are disseminated by biological vectors and then by the vegetative propagation of infected material. More than 10 viruses commonly infect the grapevine, and it is not rare to find two or three different viruses in one infected plant. There are no efficient chemical treatments against virus infections. A molecular strategy to induce virus resistance in plants is gene silencing. This strategy requires the transformation of plants with a short sequence of the pathogen in a way that a double-strand RNA structure is formed during transcription, initiating gene silencing in the host. The objective of this work was the induction of virus silencing in grapevine rootstocks in order to use them for grafting. It is expected that the mobile silencing signal would induce virus silencing in the scion. We have transformed rootstocks (110 Richter and Harmony) by co-culturing embryogenic and organogenic tissues with Agrobacterium tumefaciens carrying a silencing vector containing a sequence of the coat protein of Grapevine fanleaf virus (GFLV). Twenty-six transgenic plants of the 110 Richter rootstock have been recovered, analyzed by RT-PCR for the GFLV sequence, and propagated to obtain several plants of each line. The transgenic root¬stocks have been grafted with GFLV-infected plants that were positive for virus presence by RT-PCR analysis. Once the grafts were set, GFLV detection was carried out with scions using primers for the movement protein. After one month the detection of the virus was abolished in the scion, with three of six analyzed rootstock lines.