TRANSGENIC RESISTANCE GENES FROM NEPOVIRUSES - EFFICACY AND OTHER PROPERTIES

Evidence of RNA-RNA recombination or transcapsidation was sought in tr ansgenic tobacco (Nicotiana tabacum L. 'Xanthi-nc') containing the 3'- non coding sequence (1.3 kb) from a birch isolate of cherry leaf roll nepovirus (CLRV). Following mechanical inoculation with a rhubarb isol ate of the virus, no evidence of recombination was obtained using poly merase chain reactions whether the transgenic gene produced transcript s in the sense or the antisense orientation. Transgenic tobacco contai ning the CLRV-derived sequence (in either orientation) did not lessen the pathological effects of the rhubarb isolate of the virus although there was amelioration of the disease caused by the birch isolate. Whe n expressed as a transgenic gene in tobacco, the capsid coding sequenc e of arabis mosaic nepovirus (ArMV) lessened infectibility by nematode s carrying that virus. This construct did not influence the pathogenic ity of potato virus Y(o) (PVY(o)), tobacco rattle tobravirus (PRN), al falfa mosaic ilarvirus (AlMV), or CLRV, did not alter the levels of th eir accumulation and did not render their virions more or less prone t o recognition by ArMV-specific antibodies. Uninoculated tobacco expres sing the ArMV capsid protein contained ArMV-like particles which co-pu rified with RNA that hybridised with cDNA to tobacco mRNA and to DNA c omplementary to the capsid coding sequence.