Abstract: Three crosses，Hawaii7981 × PI128216，Hawaii7981 × LA1589 and PI128216 × LA1589，were made to develop F2 populations for testing allelisms among three genes Xv3，Rx4，and RxLA1589 for resistance to bacterial spot caused by Xanthomonas perforans race T3. Each population consisted of 535–1 655 individuals. Infiltration method was used to inoculate the parental and F2 plants as well as the susceptible control OH88119. The results showed that all plants had hypersensitive resistance to race T3 except for OH88119，indicating that Xv3，Rx4 and RxLA1589 were allelic genes. Sequences of Rx4 alleles were amplified from Hawaii7981，PI128216，and LA1589 using the gene-specific primers. No sequence variation was observed in the coding region，suggesting that the resistance to race T3 in the three resistant lines was conditioned by the same gene. These results will provide useful information for understanding the mechanism of resistance to race T3 and developing resistant variety in tomato.

Key words: tomato, tomato bacterial spot, race T3, hypersensitive resistance gene, allelic test