Abstract：Abstract: In research paper, by BLAST(Basic Local Alignment Search Tool) and HMW(Hidden Markov Wodel)analysis,a full set of disease resistance candidate genes encoding nucleotide-binding sites (NBS) in a complete genome(Mt2.0) of Medicago truncatula was identified and characterized by structural diversities, gene duplication，physical positions, phylogenetic relationships. We found 469 NBS-coding sequences which contain 446 regular NBS genes and 23 non-regular NBS genes.Meanwhile, We found significant excesses of duplications in the genome of Medicago truncatula after analysis of NBS standard physical locations and phylogenetic tree .These results suggested that gene duplication played a major role in disease resistance genes expansion .
