Fig. (5) Examples of TYLCV immunity following C2 silencing. Frame A shows TYLCV-inoculated plants. Plant I: Treated with RI-C2-RI, 3 months post-TYLCV-inoculation. Plant II: Treated with RI-C2-RI, 2 months post-inoculation. Plant III: Untreated plant, 3 months post-inoculation. Frame B: Semi-quantitative PCR. Samples were drawn every three cycles from cycle 18 to 30. Upper frames: PCR with primers for TYLCV CP (product size: 600 bp). Lower frames: PCR with primers for 18S rDNA (product size: 450 bp). SM: Size markers. Lanes 1-5: Samples from a TYLCV-infected plant (plant III in A). Lanes 6-10: Samples from an IR-C2-RI-injected, TYLCV-infected plant (plant I in A). No TYLCV was detected in the IR-C2-RI-treated plant. Frame C: Comparison of TYLCV titer in symptom-carrying and asymptomatic leaves of the same plant (plant II in A). Lanes 1-3: PCR (35 cycles) of symptom-showing leaves. Lanes 4-6: As in lanes 1-3 but from asymptomatic leaves. Lane 7: Negative control, PCR was carried out without template. Lane 8: Internal control; rDNA level from a symptomatic leaf. Lane 9: Internal control; rDNA level from an asymptomatic leaf.