BROAD RESISTANCE TO TOSPOVIRUSES IN TRANSGENIC TOBACCO PLANTS EXPRESSING 3 TOSPOVIRAL NUCLEOPROTEIN GENE-SEQUENCES

Transgenic tobacco plants have been obtained expressing nucleoprotein (N) gene sequences of three different tospoviruses known to affect veg etable crops: tomato spotted wilt virus (TSWV), tomato chlorotic spot virus (TCSV), and groundnut ringspot virus (GRSV), The chimeric plant transformation vector used comprised the three viral N gene sequences, each with a copy of the CaMV 35S promoter and the nos terminator. Des pite the high levels of homology between the different N gene sequence s (74-82%) and the presence of repeated promoter and terminator sequen ces in this construct, unrearranged copies of this triple N gene const ruct were stably maintained in both Escherichia coli and Agrobacterium tumefaciens plasmids used during the cloning process, as well as in s everal generations of transgenic tobacco plants, A transgenic tobacco line was obtained that exhibited high levels of resistance to all thre e tospoviruses, showing the possibility of producing transgenic plants with a broad resistance to tospoviruses by introducing tandemly clone d viral N gene sequences. DNA analysis of this transgenic plant line s hows that the multivirus resistance trait is confined to a single gene tic locus, which is very convenient for further breeding purposes.