小麦抗赤霉病主效QTL Qfh.nau-2B的精细定位和效应评价

Fusarium head blight (FHB) is a devastating wheat disease. Digging out and utilizing resistance genes is the most effective and most economic solution to control this disease. Several FHB resistance QTLs have been mapped, but not many were further studied and applied, and these QTLs cannot meet the needs of resistance breeding in practice. In a previous study, Qfh.nau-2B identified in Nanda 2419 was related to multiple components of FHB resistance and its resistance effect was validated by developing its near isogenic line (NIL) using Mianyang 99-323 as recurrent parent. In this project, all the available sequence will be exploited to develop molecular markers linked with Qfh.nau-2B, then a high-density genetic map will be constructed using Nanda 2419-Wangshuibai RIL population and a secondary F2 population derived from Qfh.nau-2B NIL crossed with its recurrent parent, and many plants with recombination occurring within the Qfh.nau-2B interval in two populations above will be identified and evaluated to fine map Qfh.nau-2B. To further evaluate the effect of Qfh.nau-2B, it will be transferred to other genetic backgrounds by marker-assisted selection in this project. The implementation of this project could help to elucidate the genetic basis of Qfh.nau-2B resistance, lay the foundation for the effective use and map based cloning of this QTL, have important practical value to FHB resistance breeding.

赤霉病是小麦生产上的一种毁灭性病害。抗病基因的发掘和应用是防治赤霉病最经济有效的方法。目前虽然定位了许多抗赤霉病QTL,但是深入研究的并不多,且并不能满足抗赤霉病育种的需求。在前期研究中我们鉴定出Qfh.nau-2B是一个与多种赤霉病抗性相关的主效QTL ,并通过培育Qfh.nau-2B在绵阳99-323背景中的近等基因系验证了它的效应。本项目拟通过各种策略开发分子标记,利用已有的RIL群体和NIL衍生的次级F2群体构建Qfh.nau-2B区段高密度遗传图谱,并通过筛选和鉴定这两个群体中该区段的重组体对其进行精细定位。同时拟利用分子标记辅助选择的方法将它导入其他的遗传材料中进一步评价其效应。本项目的实施有助于阐明Qfh.nau-2B抗赤霉病的遗传基础,为图位克隆和有效利用该QTL奠定基础,对提高小麦综合赤霉病抗性有十分重要的应用价值。

QFhb.nau-2B是南大2419中的一个既抗赤霉病侵染又抗赤霉病扩展的QTL。本研究以感病材料川麦42和PH691为轮回亲本，利用分子标记辅助选择技术在不同的遗传背景中验证了该QTL的效应。为了精确定位QFhb.nau-2B，利用中国春小麦参考基因组序列以及90K SNP芯片数据，在QFhb.nau-2B区间开发了20个在望水白和南大2419之间有多态的分子标记。利用QFhb.nau-2B区间在Xwmc474-Xmag1729发生重组的138个株系，构建了一个包含43个多态性分子标记总长为18.2 cM的高密度遗传图谱，平均每厘摩有两个分子标记。在这些重组体中，利用反向选择其他抗赤霉病QTL位点，筛选到的19个和20个在QFhb.nau-2B区段发生重组且不含其它抗病位点、分别与Type I和Type II相关的重组体，基因型检测结果表明与两种抗性相关的重组体均可以代表13种重组类型。对这些重组体的田间表型鉴定结果表明，重组体间抗感差异显著，可明显分为抗、感两类。综合重组体的基因型和表型，将QFhb.nau-2B的Type I的抗性定位到相距0.9 cM的Xwgrb1561-Xwgrb1410之间；将Type II的抗性定位到相距4.1 cM的Xwgrb1503-Xwgrb1373之间。其中Type II的抗性区间包含Type I的区间。与QFhb.nau-2B紧密连锁的分子标记的开发有利于该QTL在育种项目中的利用。