Engineering cherry rootstocks with resistance to Prunus necrotic ring spot virus through RNAi-mediated silencing

Prunus necrotic ringspot virus (PNRSV) is a major pollen-disseminated ilarvirus that adversely affects many Prunus species. In this study, an RNA interference (RNAi) vector pART27-PNRSV containing an inverted repeat (IR) region of PNRSV was transformed into two hybrid (triploid) cherry rootstocks, Gisela 6' (GI 148-1) and Gisela 7'(GI 148-8)', which are tolerant and sensitive, respectively, to PNRSV infection. One year after inoculation with PNRSV plus Prune Dwarf Virus, nontransgenic Gisela 6' exhibited no symptoms but a significant PNRSV titre, while the transgenic Gisela 6' had no symptoms and minimal PNRSV titre. The nontransgenic Gisela 7' trees died, while the transgenic Gisela 7' trees survived. These results demonstrate the RNAi strategy is useful for developing viral resistance in fruit rootstocks, and such transgenic rootstocks may have potential to enhance production of standard, nongenetically modified fruit varieties while avoiding concerns about transgene flow and exogenous protein production that are inherent for transformed fruiting genotypes.