EVALUATION OF TRANSGENIC TOMATO PLANTS EXPRESSING THE COAT PROTEIN GENE OF CUCUMBER MOSAIC-VIRUS STRAIN WL UNDER FIELD CONDITIONS

Transgenic tomato plants expressing the coat protein (CP) gene of cucu mber mosaic virus (CMV) strain WL, a member of CMV subgroup II, were e valuated for resistance to CMV infections under field conditions for 2 years. Three transgenic inbred lines, two hemizygous and one homozygo us, and one transgenic hybrid were field tested. CMV subgroup I strain Fny was used as challenge inoculum. Disease incidence was assessed by monitoring symptom development, enzyme-linked immunosorbent assays (E LISA), and bioassays on indicator hosts. The four transgenic tomato li nes exhibited a high level of resistance to CMV infections, since all 747 transgenic plants remained symptomless throughout the crop cycle. Moreover, CMV could not be detected by ELISA nor recovered from uninoc ulated leaves of transgenic plants. These developed to normal height, and showed a 17-fold increase in productivity along with a 44% increas e in fruit weight compared with nontransformed control plants. Since o ur transgenic CMV-resistant homozygous tomato line also has resistance to TMV that is conferred by the Tm-2(2) gene in the parental cultivar , it can be used as a breeding germ plasm to develop commercial hybrid s resistant to both CMV and TMV, two important viruses that affect tom ato crops.