水稻协优9308重组自交系群体白叶枯病抗性的全基因组关联分析

Genetic dissection of the bacterial blight disease resistance in super hybrid rice RILs using genome-wide association study

白叶枯病是水稻生产最严重的细菌性病害,挖掘新的白叶枯病抗性基因资源并培育抗病品种是控制该病害的重要方法。本研究利用父母本抗性差异较大的协优9308衍生的139个重组自交系群体作为遗传材料,人工接种不同白叶枯菌后的病斑长度作为连续型表型,结合经DNA深度测序获得的476,505个单核苷酸多态性(single-nucleotide polymorphism,SNP)标记进行全基因组关联分析(genome-wide associated study,GWAS)。结果表明在P<1×10^(-4)下,4个菌株处理后共鉴定到109个与白叶枯抗性显著关联的SNPs位点,解释表型变异率59.78%~63.29%。其中CR4接种发现了25个SNP位点其贡献率为61.00%,在这些SNP位点附近共筛选到19个基因,其中有2个为NBS-LRR抗病相关基因(LOC_Os11g43420和LOC_Os11g45930)。表达分析验证发现该2个基因在抗性亲本中恢9308的表达量分别为感病母本协青早B的4.42倍和8.86倍,表明其可能在正调控白叶枯病抗性机制中发挥重要作用。进化树分析发现这2个候选基因与已克隆的抗性基因属于不同的亚组,表明可能是新基因。本研究为进一步挖掘白叶枯抗性基因和培育抗病品种提供了理论基础和基因资源。

Bacterial blight caused by Xanthomonas oryzae pv.oryzae is the most destructive bacterial disease in rice production,and cultivating new disease-resistance variety by mining and utilizing the novel disease resistance genes is one of the most effective ways to control this disease.In our study,a population of 139 recombinant inbred lines(RILs)derived from super hybrid rice Xieyou 9308,between the parents of which there was genetic difference in resistance to bacterial blight,were inoculated with four Xoo strains.A genome-wide association study(GWAS)was carried out using 476,505 SNPs for the lesion length as a quantitative phenotype.The result revealed that a total of 109 significant SNPs including two genes encoding NBS-LRR containing proteins were detected to be significantly difference at P<1×10^(-4) for four Xoo strains-treated lesions,accounting for phenotype variation of 59.78%-63.29%,respectively.Furthermore,25 SNPs located in/nearby 19 candidate genes were identified by the CR4 inocula-tion,accounting for 61.00%.Relative expression analysis of two selected candidate genes,LOC_Os11g43420 and LOC_Os11g45930,demonstrated their higher expression levels in the resistant cultivar Zhonghui 9308 than in the susceptible variety Xieqingzao B,suggesting that these two genes might positively regulated bacterial blight resistance.Phylogenetic tree analysis indicated that these two genes were different from the previous cloned resistant genes in evolution,suggesting they were novel disease resistance genes.These results lays a theoretical basis and provides genetic resources for future resistant breeding in rice.