LONG-TERM RESISTANCE TO TOMATO SPOTTED WILT VIRUS IN TRANSGENIC TOBACCO CULTIVARS EXPRESSING THE VIRAL NUCLEOPROTEIN GENE - GREENHOUSE AND FIELD-TESTS

We examined the resistance phenotype of a large number of transgenic t obacco plants originating from 12 commercial (Nicotiana tabacum) culti vars expressing the sense form of the nucleoprotein (N) gene of L3, a Bulgarian isolate of tomato spotted wilt virus (TSWV). The analysis re vealed that transgenic plants are completely protected against the hom ologous L3 isolate of TSWV irrespective of whether or not they contain detectable levels of translational product. The effectiveness of prot ection against the virus was investigated upon mechanical inoculation under greenhouse conditions and in field trials. Non-segregating resis tant lines were selected and the inheritance of the resistance to TSWV was analysed in successive generations (R-3-R-6) Extensive tests unde r controlled conditions and two-year field trials proved that the resi stance to TSWV is stable in different environments and is a stably inh erited trait.