The tomato gene Sw5 is a member of the coiled coil, nucleotide binding, leucine-rich repeat class of plant resistance genes and confers resistance toTSWV in tobacco

Tomato spotted wilt virus is an important threat to tomato production world wide. A single dominant resistance gene locus, Sw5, originating from Lycope rsicon peruvianum, has been identified and introgressed in cultivated tomat o plants. Here we present the genomic organization of a 35 250 bp fragment of a BAC clone overlapping the Sw5 locus. Two highly homologous (95%) resis tance gene candidates were identified within 40 kb of the CT220 marker. The genes, tentatively named Sw5-a and Sw5-b, encode proteins of 1245 and 1246 amino acids, respectively, and are members of the coiled-coil, nucleotide- binding-ARC, leucine-rich repeat group of resistance gene candidates. Promo ter and terminator regions of the genes are also highly homologous. Both ge nes significantly resemble the tomato nematode and aphid resistance gene Mi and, to a lesser extent, Pseudomonas syringae resistance gene Prf. Transfo rmation of Nicotiana tabacum cv. SR1 plants revealed that the Sw5-b gene, b ut not the Sw5-a gene, is necessary and sufficient for conferring resistanc e against tomato spotted wilt virus.