Abstract：The nucleotide binding site (NBS) - leucine-rich-repeat (LRR) gene family is the largest group of resistance genes cloned from plant to date. They play important roles during pathogen infection and expansion in plants. To characterize the sequences and their conserved domains of NBS-LRR type of resistance genes in tomato(Solanum lycopersicum L.), degenerate primers were designed using sequences of conserved domains and used to amplify resistance gene analogs (RGAs) from six tomato lines OH88119, Ha7981, Ha7998, PI114490, PI128216, and TR. The PCR products were sequenced and the sequences were subjected to evolutionary analysis. A total of 157 RGAs scattering on 12 chromosomes were isolated. The deduced amino acid sequences of all RGAs contained domains such as P-loop, Kinase2, Kinase3 and GLPL, which were conserved among NBS-LRR resistance genes. Phylogenetic analysis divided these RGAs into two classes, toll interleukin-1 receptor domain (TIR)-NBS-LRR and coiled-coil (CC)-NBS-LRR. These results will provide some information for isolation of disease resistance genes and marker-assisted selection in tomato.
