Stability of resistance against beet curly top disease in the presence of cucumber mosaic virus in Arabidopsis thaliana

Curly top is one of the most important viral diseases of sugar beet. Use of resistance sources is a promising strategy for control of this disease. In the present study, the efficiency of four gene silencing constructs (OUT-hp، IN-hp، sense and antisense) against two major causes of curly top disease in Iran, beet curly top virus-Svr (BCTV) and beet curly top Iran virus (BCTIV), were evaluated in transgenic plants. Selection of transgenic plant seeds was carried out on selective medium 1/2MS containing glufosinate-ammonium (Basta) and the results showed that the pBCTV-IN-hp construct resulted in the highest germinated seeds. Selected plants were transferred to greenhouse and evaluated for resistance to basta and detection of silencing constructs in the transgenic plants. Afterwards, resistance of the selected transgenic plants to beet curly top viruses and resistance stability against cucumber mosaic virus (CMV) was evaluated in a completely randomized design with six treatments in a factorial experiment. The results showed that the transformed lines with each of four constructs were significantly different in severity of symptoms, plant height and number of flowering stems compared to their respective controls. Although these transgenic plants were resistant to BCTV-Svr and BCTIV, in their challenge inoculation experiments it was shown that this resistance was suppressed by CMV infection.