三个抗纹枯病主效QTLs在粳稻中的育种利用基础研究

Sheath blight (SB) is one of the three most serious diseases in rice. Resistance to rice SB is controlled by polygenes. It is too difficult to develop SB resistance variety by conventional breeding strategy. In total, japonica rice varieties showed more susceptible to SB disease than indica rice varieties; therefore, it is more urgent to improve the SB resistance of japonica rice variety. Previous studies have showed that marker-assisted selection (MAS) for SB resistance QTLs (SBR QTLs) is a feasible strategy to develop SB resistance variety. However, since the theoretical basis associated with the utilization of SBR QTLs in rice breeding is not far enough, the progress in utiliization of SBR QTLs by MAS has been very slow. . In previous studies, we have identified three major SBR QTLs from three indica rice varieties, respectively. According to the donor parents of the resistant allele(s) of each SBR QTL, we named them as qSB-12-2YSB, qSB-11HJX and qSB-9TQ, respectively. All the three SBR QTLs have been further mapped in the regions less than 3 cM. Among them, qSB-12-2YSB showed greatest effects on controlling SB disease compared to all SBR QTLs identified in our previous studies. On the base of these results, in this project we will investigate 1) the distribution and effects of qSB-12-2YSB and qSB-11HJX in different japonica rice varieties; 2) the resistance effects of the three SBR QTLs to different SB isolates collected from different rice ecological regions; 3) the interaction modes among the three SBR QTLs and the resistance effects of different combinations of the three SBR QTLs. Results in this study will determine the breeding value and the best ultilizing strategy of the three SBR QTLs in improving SB resistance of japonica rice varieties, and will develop new rice lines with excellent resistance to SB disease, and will rich theoretical knowledge in marker-assisted breeding by using SBR QTLs.

纹枯病是水稻三大病害之一，水稻对其抗性受多基因控制，采用传统育种手段难以培育抗病品种。粳稻对纹枯病抗性总体弱于籼稻，抗性改良更为迫切。研究表明抗纹枯病QTL标记辅助选择是培育抗病品种可行途径。然而，与抗纹枯病QTL育种应用相关的理论基础还相当薄弱，严重影响其应用进程。.我们在3个籼稻中分别鉴定到1个主效抗纹枯病QTL，命名为qSB-12-2YSB、qSB-11HJX和qSB-9TQ，其中qSB-12-2YSB是迄今发现的效应最大的抗纹枯病QTL，三个QTL均被定位在3cM以内。在此基础上，本项目将研究1）qSB-12-2YSB和qSB-11HJX在不同粳稻品种中的分布情况及效应稳定性；2）三个QTL对不同地域的纹枯病菌株的抗性效应；3）三个QTL不同组配方式下的互作特征及抗性效应。研究将明确这些QTL在粳稻抗纹枯病育种中的应用价值和最佳组配模式，丰富水稻抗纹枯病分子育种理论。

纹枯病是世界性水稻病害之一，在我国，无论是发生面积还是为害造成的损失总量均居各病害之首，已经成为危害水稻最严重的病害。究其原因，主要是推广种植的水稻品种抗病水平低，且粳稻品种的纹枯病抗性水平有普遍低于籼稻的趋势。选育抗病品种是抵御病害最经济有效的方法。水稻对纹枯病的抗性为典型数量性状，分子标记辅助选择抗纹枯病QTL育种是当前可行的抗病育种策略。本项目对前期发现的两个大效应抗纹枯病QTLqSB-12-2YSB和qSB-11HJX以及qSB-9TQ开展分子育种基础研究，具有重要的理论价值和实践意义。.本项目通过杂交、回交，结合分子标记辅助选择，将抗纹枯病QTLqSB-12-2YSB和qSB-11HJX分别导入不同来源的9个代表性粳稻品种，构建不同背景带有不同目标QTL近等基因系，并在部分粳稻背景实现目标QTL两两聚合。纹枯病抗性接种鉴定结合基因型分析，获得以下结果：（1）qSB-11HJX为隐性遗传而qSB-12-2YSB为显性遗传，在不同组合背景下，各抗病基因纯合型相对于感病基因纯合型间的病级相差均在1.0级左右；（2）在这两个基因座位上，测试的9个代表性粳稻品种均带感病等位基因，暗示这两个抗纹枯病数量基因可广泛用于粳稻品种的纹枯病抗性改良；（3）在各基因的回交高世代株系（BCnF3-4）中，携带抗病等位基因的株系对纹枯病的抗性水平均得到了显著或极显著改进，但总体以携带qSB-12-2YSB株系的抗性提升最大；（4）在连粳6号和南粳9108背景下，分别研究了qSB-11HJX和qSB-9TQ、qSB-12-2YSB和qSB-11HJX以及qSB-12-2YSB和qSB-9TQ这3组QTL聚合系的抗病效应，发现聚合系的抗性效应均显著高于携带单个抗性QTL株系，表明通过不同QTL的聚合可以进一步提高粳稻的纹枯病抗性水平。以上研究结果为进一步开展水稻抗纹枯病分子育种提供新的思路和抗病种质。