[Molecular mapping of a bacterial blight resistance gene Xa-25 in rice]

Xa-25 was a bacterial blight resistance gene identified in a somaclonal mutant HX-3. A doubled-haploid (DH) population including 129 stable lines was derived from anther culture of a typical japanica 02428 and a typical indica HX-3 cross. The bacterial blight strain Zhe173, a typical bacterial blight strain in Yangtze River valley, was used to test the resistance or susceptible of the DH population lines, and the results showed that the resistance lines and susceptible lines were 62 and 67, respectively. A total of 300 SSR primer pairs covering 12 rice chromosomes were used for polymorphism survey of 02428 and HX-3. Among these primers, 74 showed polymorphism between the parents. Using these polymorphic SSR markers, bulked segregant analysis was conducted on the DH population. As the result, Xa-25 was located at the terminal region of the long arm of chromosome 4 between the two SSR markers RM6748 and RM1153, the map distance between Xa-25 and the two SSR markers was 9.3 cM and 3.0 cM, respectively.