Abstract: The near isogenic line (NIL) with a new gene Xa23 for resistance to bacterial blight (BB) was developed and designated as CBB23 in 1993-1998. A susceptible indica variety JG30 with improved plant type was used as a recurrent parent. The progenies derived from the cross JG30/H₄ harboring the gene Xa23 were developed by back cross until BC₅, and selfing for 4 times. Evaluation of the resistance gene Xa23 with specific strain P6 and selection of plant type successively were carried out till the line showing stable resistance and agronomic characters similar to the recurrent parent. Comparison of reaction for resistance spectrum to 20 strains including 10 Philippine races, 3 Japanese races, and 7 Chinese pathotypes between CBB23(carrying Xa23 )and IRBB21(carrying Xa21) was made. Xa23 is resistant to all 20 strains, and Xa21 is resistant to 19 strains and highly susceptible to the Philippine race 10. The NIL CBB23 was used to establish segregation populations of JG30/CBB23 for mapping the gene Xa23. The gene was located on rice chromosome 11 in the preliminary tagging by screening SSR. Three AFLP markers screened are closely linked with Xa23. The genetic distance between APKj23 and Xa23 is about 1.0 cM. The NIL is also valuable in rice breeding.

Key words: near isogenic line, breeding, resistance, gene, bacterial blight, rice

摘要： 1993～1998年,构建了携有抗稻白叶枯病新基因Xa23的近等基因系,命名为CBB23。以全生育期高度感病并具有改良株型的籼稻品种JG30为轮回亲本，与携有Xa23的抗性供体H-4杂交，JG30/H-4的F1通过回交、自交直至B5F4，各世代均用与目标基因Xa23相对应的专化小种菌系P6人工接种鉴定，同步进行株型和农艺性状选择，直至抗性稳定和农艺性状类似其轮回亲本。比较了CBB23 (携Xa23) 和IRBB21 (携Xa21) 对20个菌系包括10个菲律宾小种、3个日本小种和7个中国病原型代表菌系的抗谱，Xa23抗所有20 个菌系； Xa21 抗19个菌系，对菲律宾10号小种则高度感病。用近等基因系CBB23构建了JG30/CBB23组合的F2分离群体，通过SSR标记筛选，初步将Xa23定位于水稻第11染色体。进一步筛选出3个与Xa23更紧密连锁的AFLP标记。其中的APKj23与Xa23之间的图距约为1.0 cM。并报道了在抗病育种中已有效的应用了携有Xa23的近等基因系 CBB23。

关键词: 近等基因系, 育种, 抗性, 基因, 白叶枯病, 水稻