Tolerance to Citrus mosaic virus in transgenic trifoliate orange lines harboring capsid polyprotein gene

Trifoliate orange plants (Poncirus trifoliata) were transformed with a binary vector containing the capsid polyprotein (pCP) gene of Citrus mosaic virus (CiMV) via Agrobacterium tumefaciens LBA4404. Transformation was performed on the epicotyl segments obtained from a young seedling that was grown in the dark. Southern blot hybridization analysis showed that the transgene was stable in the transgenic lines after regeneration and propagation by grafting. Transgenic lines were screened for tolerance to CiMV by mechanical inoculation. Infection was monitored 30, 60, 90, and 120 days after inoculation by reverse transcription-polymerase chain reaction. The transgenic line 24 had the lowest infection rate (7.1%) at 60 days after inoculation, in contrast to that of nontransgenic plants (65.1%). The response of other lines to inoculation ranged from susceptibility to moderate tolerance.