分子标记辅助选择Xa23基因培育杂交稻抗白叶枯病恢复系

Enhancing Bacterial Blight Resistance of Hybrid Rice Restorer Lines through Marker-Assisted Selection of the Xa23 Gene

水稻抗白叶枯病新基因Xa23抗谱广、抗性强,被定位在第11染色体上。以携带抗白叶枯病基因Xa23的抗病品系CBB23为抗源,以优良杂交稻亲本9311和1826为受体材料,采用杂交和复交,在分离群体中利用与Xa23紧密连锁的EST标记C189进行分子标记辅助选择,通过苗期分子标记检测和成株期农艺性状选择,获得160份目标基因纯合且农艺性状稳定的株系。使用鉴别菌系P6,采用人工剪叶接种法,在苗期和孕穗期对21份重点株系进行了抗性鉴定,所有株系在苗期和孕穗期都表现抗病。同时对3个不育系与其中5个株系配制的15个杂交组合进行了抗性鉴定,所有组合在苗期表现抗或中抗,在孕穗期表现抗。对其中6个杂交组合进行了品比试验,2个组合产量略低于对照两优培九,其余4个组合的产量均高于两优培九,用于测配的3个株系C6201、C6271和C6351有望作为杂交稻恢复系在生产中应用。研究表明在育种进程中利用与Xa23基因紧密连锁的分子标记C189开展抗白叶枯病分子标记辅助育种是一种有效的途径。

The bacterial blight （BB） of rice is caused by the pathogen Xanthomonas oryzae pv. oryzae （Xoo）. BB is one of the most important rice diseases all over the world. The most effective and economical approach for BB control in rice production is using BB-resistant cultivars. The broad-spectrum BB resistance gene Xa23 was originally identified from wild rice species Oryza rufipogon. Xa23 was introduced into cultivated rice variety JG30 by cross and continuous back-crosses, which resulted in the near-isogenic line CBB23. In our previous studies, Xa23 was mapped on the long ann of rice chromosome 11. In this study, we used CBB23 as Xa23 donor and the elite but BB susceptible restorer lines 9311 and 1826 as recipients to develop BB-resistant restorer lines of hybrid rice. The Xa23-1inked EST marker C189 was used to select Xa23 in the segregating populations. Marker-assisted selection （MAS） for Xa23 was performed at the seedling stage of plants and followed by conventional selection for agronomic traits at the adult stage. More than 160 introgression lines that harbored homozygous Xa23 and showed stable agronomic traits were obtained. Twenty-one of the introgression lines were subject to BB disease inoculation at the seedling and booting stages in green house, and results showed that all the tested lines were resistant to the most destructive Xoo strain PXO99（P6） while the recipient parents 9311 and 1826 were highly susceptible at both stages. In addition, we used 5 of the introgression lines as restorer lines to make hybrids by crossing them with 3 sterile lines Pei＇ ai 64S, Guangzhan 63S and Yuetai A. BB-inoculation tests showed the 15 hybrids were resistant or moderately resistant to PXO99 at the seedling stage and highly resistant at the booting stage. Field trials of 6 selected hybrids showed that yields of the hybrids were equal to or even higher than that of the control super hybrid rice Liangyou Peijiu. The lines C6201, C6271 and C6351 obtained in this study are hopeful of being restorer lines of hybrid rice with great potential for commercialization in the near future. These resuhs clearly suggested that the Xa23-1inked marker C189 could be effectively utilized in the BB-resistance breeding programs.