Agrobacterium-mediated genetic transformation of the clonal 146-2 rootstock for plum and apricot by vector for RNA-interference silencing the translation initiation factor eIF(iso)G gene

The method of RNA interference gene expression silencing was used to obtain plum pox virus (PPV) resistant rootstock plants. For this, a vector with self-complementary sequences of the 578 bp eIF(iso)4G gene fragment was created. The eIF(iso)4G gene encodes a translation initiation factor involved in the life cycle of a Sharka virus. A strong promoter of the ribulose-1,5-bisphosphate carboxylase/ oxygenase (RuBisCo) gene was chosen to drive the expression of RNA interference hairpin. Successful genetic transformation of the 146-2 Russian rootstock for plum and apricot was carried out by A. tumefaciens CBE21 strain. Whole leaves from in vitro cultured shoots were used as an explant source. The nptII gene coding for neomycin phosphotransferase II was exploited as a plant-selectable marker. In our experiments, 5 independent transgenic lines were obtained and acclimatized to greenhouse conditions. Their status was confirmed by PCR and Southern blot analyses. The transformation efficiency was 0.3-0.4%. One of these lines was grafted with PPV-infected plum buds and its resistance was verified by ELISA.