【摘要】 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。更多还原

【Abstract】 The horizontal resistance of rice to a virulent bacterial blight Xanthomonas oryzae pv. Oryzae strain- CR6, was inveshgated using a recombinant inbred (RI) rice population from the cross ’Lemont/Teqing’. Both parents and the F1 plants were susceptible to CR6 and the lesion length (LL) of the RILs showed a continuous variation with remarkable transgressive segregation in both directions, suggesting the typical polygenic inheritance. A significant portion (9%) of the RILs showed a high level (LL≤ 3cm) resistance to CR6. Using a complete linkage map with 178 well distributed RFLP makers, eleven QTLs and 3 pairs of epistatic loci were identified which were largely responsible for the variation of LL in the RI population. The resistance QTLs locate on rice chromosomes 2, 3, 4, 8, 9, 10, 11 and 12. A QTL with a fairly large additive effect was detected at the locus of Xa-4 from Teqing.Among the other 10 QTLs, 7 resistance alleles were from Teqing, 3 from Lemont.The results indicate that the accumulative effect of multiple QTLs and the residual effect of ’defeated’ Xa-4 are the genetic basis of horizontal resistance to Xoo of rice and an important component of the resistance. It is expected that using DNA marker-aided selection, these QTLs can be combined with major resistance genes to develop rice cultivars with durable resistance to Xoo.更多还原