Abstract: Abstract： Bacterial blight (BB) caused by Xanthomonas oryzae pv oryzae (Xoo) is one of the most serious diseases in rice. Host resistance is thought to be a sound approach to control BB. A new bacterial blight resistance germplasm (Y238) was identified from the wild rice species Oryza rufipogon and the resistance locus was transferred to the susceptible Indica rice variety JG30 by cross, backcross and self-cross to BC6F3 generation. The resistance locus was tentatively designated as Xa30（t）. A BC6F2 population was used for molecular mapping of Xa30（t）. Inoculation test of the BC6F2 population at adult stage with the Philippine strain PXO99 of Xoo showed that the segregation ratio between resistant and susceptible plants was 3:1, indicating that a dominant locus controls the resistance. Bulked Segregant Analysis (BSA) was adopted to survey 343 PCR-based SSR, EST and STS molecular markers located on the twelve rice chromosomes and results showed that four markers, RM1341, V88, C189 and 03STS, displayed polymorphism between the susceptible-pool and resistance-pool. By analyzing the 303 individuals of the BC6F2 population with the mentioned four markers together with their resistance phenotypes, the gene Xa30（t）was mapped on the long arm of chromosome 11. Linkage analysis revealed that RM1341, V88, C189 and 03STS located on the same side of Xa30（t）, with genetic distances of 11.4cM, 11.4cM , 4.4 cM and 2.0 cM respectively.

Key words: Rice bacterial blight, Xa30(t), Near-isogenic line, Gene mapping