Resistance to Citrus tristeza virus in Citrus sinensis transgenic plants

Citrus tristeza virus (CTV) control relies mainly on the use of tolerant rootstocks and scion cross protection. The aim of this work was to evaluate transgenic C. sinensis lines for resistance to CTV, in order to offer another alternative for virus control. Transgenic lines of C. sinensis cv. ‘Valencia’ and ‘Hamlin’ containing one of 3 different genetic constructs (pCTV-CP: coat protein gene of CTV; pCTV-CS: conserved sequence of CTV; pCTV-dsCP: hairpin with sense and antisense sequences of the CP gene) were evaluated, totalizing 60 transgenic lines. The lines were grafted into C. limonia and C. aurantium, totaling 360 plants. The plants were challenged 4 times with CTV by means of T. citricida. Indirect ELISA using a monoclonal antibody against the CTV coat protein or Real-time PCR using primers to amplify CTV genes were used to detect the virus. Variation in the virus resistance was observed among different transgenic constructs and different clones of the same line. The virus was not detected in 20 clones of different lines even after the fourth inoculation. For ‘Hamlin’, it was possible to identify 1 transgenic line (CS9 grafted into C. limonia) with no virus multiplication. For ‘Valencia’, 1 clone of each transgenic line CP1, CP2, CP4, CP9, CS1, CS8, DS3 and DS10 grafted into C. aurantium, 1 clone of CP7, CS1, CS5, CS10 and DS3 and 2 clones of CP6, CS6 and CS7 grafted into C. limonia did not amplify the virus genes. This indicates possible resistance to the pathogen.