一个新的兼抗小麦条锈病和叶锈病成株抗性位点精细定位

Stripe (or yellow) rust and leaf (or brown) rust caused by Puccinia striiformis f. sp. tritici and Puccinia triticina, respectively, are two major wheat diseases in China. Slow rusting adult-plant resistance (APR) genes play an important role in ensuring their appropriate deployment in wheat breeding around the world. It is very important to identify closely linked/co-segregated molecular markers to APR gene for durable resistance to stripe rust and leaf rust. 3 F5 recombinant inbred lines (RILs) derived from a cross between Francolin #1 and susceptible line Avocet, which only carry APR QTL QYL.cimmyt-3DC, were separately used to cross with Avocet for constructing sub-population. The sub-population will plant in experimental stations of Huazhong Agricultural University and Hebei Agricultural University, respectively, for stripe rust and leaf rust evaluation during 2013-2015 crop seasons. Artifical inoculations in both stations will carriy out using the highly virulent P. striiformis Chinese races CYR33 and a mixture of P. triticina isolates THTT, FHTT, FHNQ and FHTS approximately one month after sowing. Disease severity of stripe rust and leaf rust on parents and lines will score twice in 2014 and 2015, respectively, according to the Modified Cobb Scale, where percentage of rust tissue is visually estimated. Stripe rust and leaf rust severity will rate when the susceptible parent Avocet displayed 90-100% severity. In order to find 2-3 co-segregated molecular makers to QYL.cimmyt-3DC, 600 BC3F2 lines will be used to fine map this locus with SSR, EST, SNP and 3D genome based markers. These molecular markers will play an important role in gene cloning and marker assistant selection for durable resistance in wheat breeding.

小麦条锈病和叶锈病是我国小麦的两大主要病害，兼抗多种病害成株抗性基因的合理利用已成为全球小麦抗病育种的重要策略，发掘与其紧密连锁或者共分离分子标记，对加速小麦条锈和叶锈持久抗病育种极为重要。本项目选用仅含成株抗性位点QYL.cimmyt-3DC的3个Avocet/Francolin #1重组自交系分别与感病亲本Avocet进行杂交并回交3次构建的次级群体进行精细定位，该群体于2013─2015分别在华中农业大学和河北农业大学试验基地进行条锈病和叶锈病成株抗性鉴定，选用小麦条锈病生理小种CYR33和叶锈病混合小种（THTT，FHTT，FHNQ和FHTS）进行人工接种。利用SSR、EST、SNP标记和小麦3D 基因组序列标记，对含有600个BC3F2家系的次级群体进行精细定位，找到与QYL.cimmyt-3DC位点共分离的2～3个分子标记，为该位点的克隆和分子标记辅助育种奠定基础。

抗病品种的利用是小麦抗条锈病和叶锈病育种的主要途径，而兼抗多种病害成株抗性基因的合理使用将成为我国小麦抗病育种的主导趋势，发掘与其紧密连锁分子标记对持久抗病育种极为重要。本项目选用598个 BC3F2家系次级群体和含有153个家系的重组自交系群体对成株抗性位点QYr.cim-3DC/QLr.cim-3DC进行精细定位，获得2对与其紧密连锁的STS标记（CS3和CS5），与目标基因的遗传距离为0.3 cM。通过对4个遗传群体条锈病和叶锈病成株抗性研究显示，在普通小麦Avocet/Kudan群体中检测到2个一因多效成株抗性位点，3个条锈病位点和2个叶锈病位点；在Avocet/Chilero群体中定位4个一因多效位点和2个条锈病成株抗性位点，其中位于1BL染色体上的位点为已知基因Lr46/Yr29；在人工合成小麦衍生系UC1110/PI610750群体中，定位到2个叶锈病成株抗性位点和3个条锈病成株抗性位点，其中位于2DS染色体的叶锈病成株抗性位点为新发现基因并纠正已命名成株抗性基因Yr48为全生育期抗性基因；最后，在硬粒小麦群体Atred#1/Bairds群体中，共检测到4个叶锈病成株抗性位点，分别位于1BL, 2BC，5BL和6BL染色体上。首次在硬粒小麦中证实Lr46的抗叶锈病效应。位于6BL染色体上的位点为新发现QTL，其毗邻的SNP标记已经转换为育种家可以直接应用的KASP标记。该项目为小麦育种家提供4对（2对STS和2对KASP）功能性分子标记，2份高度成株抗锈普通小麦和2份高度叶锈病抗性硬粒小麦，为Lr46克隆提供分子标记序列。