用水稻抗白叶枯病基因Xa23的近等基因系CBB23与其感病轮回亲本金刚30（JG30）杂交，构建了包含2562个单株的F2作图群体。用水稻白叶枯病广致病菌系P6进行抗性鉴定表明，F2植株抗感分离比严格符合3：1。根据日本水稻基因组计划RGP水稻高密度图谱上的RFLP探针对F2群体中的145个感病单株进行RFLP检测和连锁分析，获得了6个与Xa23紧密连锁的RFLP分子标记。其中RFLP标记C1003A靠着丝粒一侧，与Xa23的遗传图距为0.4cM，为Xa23的图位克隆奠定了重要基础。并将标记C1003A成功地转化为STS标记，为分子标记辅助选择育种（MAS）提供了方便有效的分子标记。
A F2 population derived from cross of the Xa23 near isogenic lines, JG30 and CBB23, was used for fine mapping of the rice bacterial blight resistance gene Xa23. Inoculation of the F2 plants with a Xanthomonas oryzae strain P6 showed a 3:1 ratio for the segregation of resistant and susceptible as expected. One hundred and forty-five susceptible plants were selected from the F2 population for mapping the gene Xa23 and fifteen restriction fragment length polymorphism (RFLP) markers anchored on the rice high-density map. A RFLP marker C1003A was found to be linked to the gene Xa23 by 0.4 cM. This result constitutes an important basis for map-based cloning of the gene Xa23. The RFLP marker C1003A was transformed into sequence-tagged-site (STS) marker, which can be applied for molecular marker-assisted selection (MAS) of Xa23 in rice breeding programs.
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