Development of Breeding Materials of Transgenic Tomato Plants with a Truncated Replicase Gene of Cucumber Mosaic Virus for Resistance to the Virus

Abstract

Tomato plants were transformed with a truncated replicase gene encoded by RNA 2 of cucumber mosaic virus (CMV) strain GT, subgroup II. The truncated replicase gene does not retain a C-terminal region of the gene that contains the GDD amino acid motif and the NTP binding motif. These motifs are considered to correspond to active and/or recognition domains of RNA-dependent RNA polymerase. Upon transformation via Agrobacterium tumefaciens, 137 individual transgenic lines were obtained. Each transgenic line was evaluated for resistance to CMV. About 10 % of the transgenic lines were highly resistant and the remaining 90 % showed a moderate resistance or were susceptible. The 15 lines were selected as resistant lines. Chenopodium amaranticolor was used to analyze the multiplication of CMV in the symptom-less plants. Among the selected lines, three lines did not appear to show any multiplication of CMV in both inoculated and non-inoculated leaves. Based on transgene amplification by PCR and the kanamycin resistance assay, the T₁ progeny of the selected lines harbored the transgene. Several resistant lines of the T₁ generation were resistant to viral inoculation. These resistant lines could become suitable breeding materials for resistance to CMV.