National Agricultural Research Center, National Agriculture and Food Research Organization, 3-1-1 Kannondai, Tsukuba 305-8666, Ibaraki, Japan.
National Agricultural Research Center, National Agriculture and Food Research Organization, 3-1-1 Kannondai, Tsukuba 305-8666, Ibaraki, Japan ; Present address: Molecular Microbiology and Biotechnology group, Research Institute of Innovative Technology for the Earth, 9-2 Kizugawadai, Kizugawa 619-0292, Kyoto, Japan.
Rice (N Y). 2014 Apr 10;7(1):2. doi: 10.1186/s12284-014-0002-9. eCollection 2014.
Rice blast is a destructive disease caused by Magnaporthe oryzae, and it has a large impact on rice production worldwide. Compared with leaf blast resistance, our understanding of panicle blast resistance is limited, with only one panicle blast resistance gene, Pb1, isolated so far. The japonica cultivar Miyazakimochi shows resistance to panicle blast, yet the genetic components accounting for this resistance remain to be determined.
In this study, we evaluated the panicle blast resistance of populations derived from a cross between Miyazakimochi and the Bikei 22 cultivar, which is susceptible to both leaf and panicle blast. The phenotypic analyses revealed no correlation between panicle blast resistance and leaf blast resistance. Quantitative trait locus (QTL) analysis of 158 recombinant inbred lines using 112 developed genome-wide and 35 previously reported polymerase chain reaction (PCR) markers revealed the presence of two QTLs conferring panicle blast resistance in Miyazakimochi: a major QTL, qPbm11, on chromosome 11; and a minor QTL, qPbm9, on chromosome 9. To clarify the contribution of these QTLs to panicle blast resistance, 24 lines homozygous for each QTL were selected from 2,818 progeny of a BC2F7 backcrossed population, and characterized for disease phenotypes. The panicle blast resistance of the lines harboring qPbm11 was very similar to the resistant donor parental cultivar Miyazakimochi, whereas the contribution of qPbm9 to the resistance was small. Genotyping of the BC2F7 individuals highlighted the overlap between the qPbm11 region and a locus of the panicle blast resistance gene, Pb1. Reverse transcriptase PCR analysis revealed that the Pb1 transcript was absent in the panicles of Miyazakimochi, demonstrating that qPbm11 is a novel genetic component of panicle blast resistance.
This study revealed that Miyazakimochi harbors a novel panicle blast resistance controlled mainly by the major QTL qPbm11. qPbm11 is distinct from Pb1 and could be a genetic source for breeding panicle blast resistance, and will improve understanding of the molecular basis of host resistance to panicle blast.
稻瘟病是由稻瘟病菌引起的一种破坏性疾病，对全球水稻生产造成了重大影响。与叶片稻瘟病抗性相比，我们对穗颈稻瘟病抗性的了解有限，迄今为止仅分离出一个穗颈稻瘟病抗性基因 Pb1。粳稻品种宫崎米表现出穗颈稻瘟病抗性，但构成这种抗性的遗传成分仍有待确定。
本研究评估了宫崎米与易感叶瘟和穗颈瘟的品种 Bikei 22 杂交衍生群体的穗颈稻瘟病抗性。表型分析表明，穗颈稻瘟病抗性与叶片稻瘟病抗性之间没有相关性。利用 112 个全基因组开发的和 35 个先前报道的聚合酶链反应（PCR）标记对 158 个重组自交系进行的数量性状位点（QTL）分析表明，宫崎米存在两个赋予穗颈稻瘟病抗性的 QTL：位于第 11 染色体上的主效 QTL qPbm11；位于第 9 染色体上的微效 QTL qPbm9。为了阐明这些 QTL 对穗颈稻瘟病抗性的贡献，从 Bikei 22 回交群体的 2818 个后代中选择了 24 个每条染色体都含有 QTL 的纯合系，并对其进行了抗病表型特征分析。携带 qPbm11 的系的穗颈稻瘟病抗性与抗性供体亲本品种宫崎米非常相似，而 qPbm9 对抗性的贡献很小。BC2F7 个体的基因型分析突出了 qPbm11 区域与穗颈稻瘟病抗性基因 Pb1 位点的重叠。逆转录 PCR 分析表明，宫崎米的穗颈中不存在 Pb1 转录本，表明 qPbm11 是穗颈稻瘟病抗性的一个新的遗传成分。
本研究表明，宫崎米含有一个由主效 QTL qPbm11 控制的新型穗颈稻瘟病抗性。qPbm11 与 Pb1 不同，可能是穗颈稻瘟病抗性的遗传来源，这将有助于理解宿主对穗颈稻瘟病抗性的分子基础。
