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利用“Lemont/特青”重组自交系（RI）群体研究了水稻对白叶枯病致病菌株CR6的水平抗性。双亲和F1均为感病，重组自交系（RILs）的病斑长度（LL）为带有明显双向超亲的连续变异，显示出典型的多基因遗传特征。部分重组自交系（约占总数90％）对CR6表现高水平抗性（LL≤3cm）。利用由178个良好分离的RFLP标记构建的饱和连锁图，鉴定出11个数量形状位点（QTLs）和3对互作位点解释了RI群体的大部分病斑变异。抗性QTLs定位于水稻第2、3、4、8、9、10、11、12等8条染色体。在来自特青的Xa－4位点上检测到一个有很大加性效应的QTL。其余10个QTLs的抗性等位基因有7个来自特青，3个来自Lemont。研究结果表明多个数量性状位点和失效主基因（Xa－4）残效的累加效应构成了对白叶枯病水平抗性的遗传基础，是重要的抗性组成部分。可以预期在DNA标记的辅助下，这些数量性状位点与主效抗性基因的组合将使水稻品种具有持久抗病性。
The resistance of rice to bacterial blight-causing bacterial strain CR6 was studied using a “Lemont / Teqing” recombinant inbred line (RI) population. Both parents and F1 were susceptible, and the lesion length (LL) of the recombinant inbred lines (RILs) was a continuous variation with a clear bi-directional super-progeny showing typical polygenic genetic features. Some recombinant inbred lines (about 90% of the total) showed high level of resistance to CR6 (LL ≤ 3 cm). Using saturation linkage maps constructed from 178 well-separated RFLP markers, 11 QTLs and 3 pairs of interaction sites were identified that explained most of the stain variation in the RI population. Resistant QTLs were located on chromosomes 2, 3, 4, 8, 9, 10, 11, 12 and other 8 chromosomes. A QTL with a large additive effect was detected at Xa-4 from Teqing. Seven of the remaining 10 QTLs had the resistance allele from Teqing and 3 from Lemont. The results showed that the additive effects of multiple quantitative trait loci and Xa-4 residues constitute the genetic basis of horizontal resistance to bacterial leaf blight and are important resistance components. It is expected that the combination of these quantitative trait loci with the major resistance genes, with the aid of DNA markers, will provide the rice variety with long-lasting disease resistance.