Evaluation of resistance in Osteospermum ecklonis (DC.) Norl. plants transgenic for the N protein gene of tomato spotted wilt virus

The nucleocapsid protein (N) gene of tomato spotted wilt virus (TSWV) was i nserted into Osteospermum ecklonis via Agrobacterium tumefaciens leaf strip s co-cultivation. Sixteen primary transformant clones of two O. ecklonis ge notypes were analysed. Southern blots of restricted genomic DNA demonstrate d integration of the transgene and indicated the number of integrated copie s. Expression of the transgene was estimated by DAS-ELISA and Western and N orthern blotting. Plants were challenged with TSWV inoculation, either mech anically or by the thrips Frankliniella occidentalis; they were then monito red for symptom appearance and tested by TAS-ELISA for infection. Inoculati on of the transgenic clones via the natural TSWV Vector was more efficient and led to the identification of 1 clone, characterised by multiple transge ne integration and no transgene expression, with improved resistance to TSW V.