Genetic Mapping Of A Bacterial Blight Resistance Gene Xa14 In Rice

Rice is one of the most important cereal crops. Bacterial blight of rice, which is a vascular bundle disease caused by Xanthomonas oryzae pv. oryzae (Xoo) , is one of the most serious diseases of rice worldwide, and leads to the yield of rice reduced greatly. So, seeking and using new bacterial blight resistance genes have become more and more important. The gene Xal4 is a dominant genes, and extremely resistant to Philippines race 5 of bacterial blight pathogen Xoo, and Taura et al. (1987) located it to the distal end on the long arm of chromosome 4. The attempt of this study about Xal4, is to construct the high-resolution likeage maps for the Xal4 region on chromosome 4 so as to finally clone them by positional cloning and have SSR markers available for MAS of Xal4. The main results are as follows:(1) Using a total of 145 highly susceptible individuals from an F2 population (775 individuals) from a cross between IRBB14 and IR24, Xal4 was located in a 0.68 cM region on the nearby end of chromosome 4, which was flanked by the molecular markers, HZR19-8 and HZR23-1, and the distance between the flank markers and Xal4 was 0.34 cM respectively, while completely cosegregated with the SSR markers, HZR21-4, HZR22-2, HZR22-5 and HZR22-7 in this population.(2)Using a total of 158 highly susceptible individuals from an F2 population (763 individuals) from a cross between IRBB14 and ZZA, the Xal4 locus was mapped to the interval of between and RM280. and was 1.90 cM away from HZR18-5 which was the closest marker flanking the Xal4 locus.(3)Combining recombination frequencies for two populations together, we mapped the Xal4 locus to 3 BAC clones spanned approximately 300 kb in length.