小麦慢白粉病QTL对条锈病和叶锈病的兼抗性

聚合兼抗白粉病、条锈病和叶锈病的慢病性基因,是培育持久多抗小麦品种的重要措施。百农64和鲁麦21均为慢白粉病品种,分别含有4个和3个慢白粉病抗性QTL。将百农64与鲁麦21杂交,获得21个聚合2~5个慢白粉病抗性QTL的F₆株系,于2012-2013年度分别在四川郫县和甘肃天水进行条锈病田间抗性鉴定,在河北保定和河南周口进行叶锈病田间抗性鉴定。分析21个株系条锈和叶锈病的最大严重度和病程曲线下面积,检测单个QTL和QTL聚合体对条锈病和叶锈病的抗性效应。结果表明,QPm.caas-4DL、QPm.caas-6BS和QPm.caas-2BL对条锈病均有显著的抗性,分别解释表型变异的16.9%、14.1%和17.3%;QPm.caas-4DL对叶锈病也有显著抗性,可解释表型变异的35.3%;QPm.caas-1A/QPm.caas-4DL/ QPm.caas-2DL/QPm.caas-2BS/QPm.caas-2BL和QPm.caas-1A/QPm.caas-4DL/QPm.caas-2BS/QPm.caas-2BL聚合体对条锈病和叶锈病的抗性显著高于两亲本,它们均含有来自百农64的QPm.caas-4DL以及来自鲁麦21的QPm.caas-2BL和QPm.caas-2BS,表明这些QTL具有明显的兼抗性效应。在小麦抗病育种中,聚合慢病性QTL越多,慢病性越强,聚合4~5个慢病性QTL时,株系可达到高抗甚至接近免疫的水平,是选育持久抗性小麦品种的重要手段。     

Transfer of rust resistance from Aegilops ovata into bread wheat (Triticum aestivum L.) and molecular characterisation of resistant derivatives

An interspecific cross was made to transfer leaf rust and stripe rust resistance from an accession of Aegilops ovata (UUMM) to susceptible Triticum aestivum (AABBDD) cv. WL711. The F₁was backcrossed to the recurrent wheat parent, and after two to three backcrosses and selfing, rust resistant progenies were selected. The C-banding study in a uniformly leaf rust and stripe rust resistant derivative showed a substitution of the 5M chromosome of Ae. ovata for 5D of wheat. Analysis of rust resistant derivatives with mapped wheat microsatellite makers confirmed the substitution of 5M for 5D. Some of these derivatives also possessed one or more of the three alien translocations involving 1BL, 2AL and 5BS wheat chromosomes which could not be detected through C-banding. A translocation involving 5DSof wheat and the substituted chromosome 5M of Ae. ovata was also observed in one of the derivatives. Susceptibility of this derivative to leaf rust showed that the leaf rust resistance gene(s) is/are located on short arm of 5M chromosome of Ae. ovata. Though the Ae. ovatasegment translocated to 1BL and 2AL did not seem to possess any rust resistance gene, the alien segment translocated to 5BS may also possess gene(s) for rust resistance. The study demonstrated the usefulness of microsatellite markers in characterisation of interspecific derivatives. This revised version was published online in August 2006 with corrections to the Cover Date.     

CIMMYT小麦种质C615抗叶锈病QTL分析

由Puccinia triticina引起的叶锈病是小麦主要病害之一, 引进种质C615具有叶锈病成株期抗性, 但其抗病性遗传机制尚不清楚。本研究以抗病亲本C615与高感叶锈病亲本宁麦18构建的F_2:7代重组自交系群体为材料, 利用337对多态性SSR标记构建遗传连锁图谱, 结合2016、2017连续两年的叶锈病鉴定结果进行复合区间作图, 结果在1BL、2DS、3BS、4DL和6BS染色体上共发现了5个抗性QTL, 暂命名为QLr.njau-1BL、QLr.njau-2DS、QLr.njau-3BS、QLr.njau-4DL和QLr.njau-6BS。其中, QLr.njau-1BL、QLr.njau-3BS和QLr.njau-4DL在两年均被检测到, 分别解释10.1%~15.7%、10.9%~13.5%和8.2%~9.0%的表型变异; 另2个QTL只在一年被检测到, 解释6.2%和9.2%的表型变异。除QLr.njau-2DS外的4个抗性QTL均来源于抗病亲本C615。QLr.njau-1BL和QLr.njau-4DL分别与已报道的慢病性基因Lr46、Lr67在同一区域, QLr.njau-3B可能为一个新的抗叶锈病QTL。此外, 本研究在C615/扬麦13 (轮回亲本)BC₄F₅回交群体中选出了15个农艺性状优良且抗叶锈病的株系, 利用与C615所含抗性QTL紧密连锁的7个SSR标记对其进行基因型检测, 结果显示所有这15个株系均含有来自C615的抗性QTL, 且有3个株系聚合了全部抗性位点, 表明C615可作为抗源亲本用于高产、抗病育种。本研究结果将为分子标记选育抗叶锈品种提供材料和技术支撑。     

QTL mapping of adult‐plant resistance to stripe rust in a ‘Lumai 21 × Jingshuang 16’ wheat population

Stripe rust, caused by Puccinia striiformis f. sp. tritici, is a devastating fungal disease in common wheat (Triticum aestivum L.) worldwide. Chinese wheat cultivars ‘Lumai 21’ and ‘Jingshuang 16’ show moderate levels of adult‐plant resistance (APR) to stripe rust in the field, and they showed a mean maximum disease severity (MDS) ranging from 24 to 56.7% and 26 to 59%, respectively, across different environments. The aim of this study was to identify quantitative trait loci (QTL) for resistance to stripe rust in an F₃ population of 199 lines derived from ‘Lumai 21’ × ‘Jingshuang 16’. The F₃ lines were evaluated for MDS in Qingshui, Gansu province, and Chengdu, Sichuan province, in the 2009–2010 and 2010–2011 cropping seasons. Five QTL for APR were detected on chromosomes 2B (2 QTL), 2DS, 4DL and 5DS based on mean MDS in each environment and averaged values from all three environments. These QTL were designated QYr.caas‐2BS.2, QYr.caas‐2BL.2, QYr.caas‐2DS.2, QYr.caas‐4DL.2 and QYr.caas‐5DS, respectively. QYr.caas‐2DS.2 and QYr.caas‐5DS were detected in all three environments, explaining 2.3–18.2% and 5.1–18.0% of the phenotypic variance, respectively. In addition, QYr.caas‐2BS.2 and QYr.caas‐2BL.2 colocated with QTL for powdery mildew resistance reported in a previous study. These APR genes and their linked molecular markers are potentially useful for improving stripe rust and powdery mildew resistances in wheat breeding.     

兼抗型成株抗性小麦品系的培育、鉴定与分子检测

小麦条锈病、叶锈病和白粉病是我国小麦的重要真菌病害,培育兼抗型成株抗性品种是控制病害最为经济有效和持久安全的方法。本研究选用由成株抗性育种方法培育的21份冬小麦高代品系和96份春小麦高代品系,在多个环境下进行这3种病害的成株期抗性鉴定,并利用紧密连锁的分子标记检测了兼抗型基因Lr34/Yr18/Pm38、Lr46/Yr29/Pm39和Sr2/Yr30的分布。田间鉴定表明,21份冬小麦品系中有17份兼抗3种病害,占80.9%;96份春小麦品系中有85份兼抗3种病害,占88.5%。分子标记检测发现,21份冬小麦品系均含QPm.caas-4DL,其中7份还含QPm.caas-2BS,9份还含QPm.caas-2BL;96份春小麦品系中,18份含Lr34/Yr18/Pm38,37份含Lr46/Yr29/Pm39,29份含Sr2/Yr30。以上结果表明,分子标记与常规育种相结合,可有效培育兼抗型成株抗性品种,为我国小麦抗病育种提供了新思路。     

川麦42的1BS染色体臂对小麦主要农艺性状的遗传效应

川麦42的1BS染色体臂来源于人工合成小麦亲本Syn769。利用川麦42与含1BL/1RS易位系的四川小麦品种川农16构建的127个重组自交系(RIL, F₈),经3年4个环境的遗传评价,比较了川麦42的1BS和川农16的1RS染色体臂对小麦产量构成因子和产量的遗传效应。结果表明,RIL群体中川麦42的1BS染色体臂株系和川农16的1RS染色体臂株系在分蘖力、成穗率、全生育期、小穗数、收获指数和籽粒产量6个性状上存在显著差异; 1BS染色体臂有利于提高成穗率和收获指数,而1RS染色体臂有利于提高分蘖能力和增加小穗数,1BS株系的籽粒平均产量比1RS株系增加2.91%。鉴于1RS染色体臂上的抗条锈病基因丧失抗性,其携带的黑麦碱基因对加工品质有明显的负向作用,而川麦42的1BS染色体臂携带高抗条锈病基因YrCH42, 并对小麦籽粒产量有正向作用,因此建议在小麦遗传改良中利用川麦42的1BS替换1RS染色体臂。     

小麦品种周麦22抗叶锈病的QTL定位

小麦叶锈病（leaf rust）是对小麦危害最严重的真菌病害之一,原菌群体中新致病菌类型的不断出现导致部分抗叶锈病基因的抗性功能逐步丧失,不断发掘和研究利用新抗源基因、培育种植抗病品种是控制该病害最有效的方法。周麦22在田间成株期对叶锈病表现出良好的抗性,为解析周麦22成株期抗叶锈病的遗传基础,将周麦22与铭贤169杂交构建遗传群体,获得255个F_2:3家系群体,经2个年度的大田成株期抗叶锈病鉴定,并利用复合区间作图法对该群体的抗叶锈病QTL进行定位分析。结果显示,该群体成株期检测到2个抗叶锈病QTL位点,分别位于1BL和2BS染色体上,命名为QLr.hebau-1BL和QLr.hebau-2BS,分别解释9.62%~11.88%和16.89%~20.99%的表型变异,该位点对叶锈病抗性表现稳定,均来自抗病品种周麦22。初步的遗传定位结果显示,QLr.hebau-2BS可能为已知抗叶锈病基因LrZH22,而QLr.hebau-1BL是新的抗病QTL。     

小麦新品种“山农20”抗病基因的分子检测

山农20是2011年和2012年分别通过国家黄淮南、北片审定的小麦高产多抗新品种,在国家区试抗病性鉴定和生产中都表现出良好的抗黄淮麦区主要病害的特性。本研究利用与小麦抗白粉病、条锈病、叶锈病、纹枯病基因和抗赤霉病主效QTL紧密连锁的SSR、SCAR、STS等标记对该品种进行了分子检测,发现山农20含有6个抗白粉病基因(Pm12、Pm24、Pm30、Pm31、Pm35和Pm36),6个抗条锈病基因(Yr5、Yr9、Yr15、Yr24、Yr26和YrTp1),2个抗叶锈病基因(Lr21和Lr26),1个抗纹枯病基因(Ses1),但未检测到抗赤霉病主效QTL。分子检测结果部分解释了山农20的优良抗病性,也为利用分子标记辅助选择培育抗病稳产小麦新品种提供参考。     

Molecular genetics of race non-specific rust resistance in wheat

Over 150 resistance genes that confer resistance to either leaf rust, stripe rust or stem rust have been catalogued in wheat or introgressed into wheat from related species. A few of these genes from the ‘slow-rusting’ adult plant resistance (APR) class confer partial resistance in a race non-specific manner to one or multiple rust diseases. The recent cloning of two of these genes, Lr34/Yr18, a dual APR for leaf rust and stripe rust, and Yr36, a stripe rust APR gene, showed that they differ from other classes of plant resistance genes. Currently, seven Lr34/Yr18 haplotypes have been identified from sequencing the encoding ATP Binding Cassette transporter gene from diverse wheat germplasm of which one haplotype is commonly associated with the resistance phenotype. The paucity of well characterised APR genes, particularly for stem rust, calls for a focused effort in developing critical genetic stocks to delineate quantitative trait loci, construct specific BAC libraries for targeted APR genes to facilitate robust marker development for breeding applications, and the eventual cloning of the encoding genes.     

以关联分析发掘小麦整穗发芽抗性基因分子标记

利用分布于小麦全基因组的181对分子标记,分析264份自然群体的基因型,采用TASSLE软件的GLM和MLM模型检测与整穗发芽抗性紧密关联的标记位点,发掘相关位点内的优异等位变异。在2012年和2013年室内整穗发芽率、2013年田间自然降雨整穗发芽率3个环境中,共关联到20个显著位点(P<0.05),分布于小麦染色体1AS、2DS、3AS、3BL、4AL、5AS、5BL、6BS、6DS、7AL和7BL上。分别位于2DS和7BL上的分子标记gwm102和barc340同时在3个环境下关联到,属于稳定的抗性位点; 另有6个标记位点同时在2个环境下关联到; 其余12个标记位点仅在1个环境下关联到。位于7BL上的barc340标记位点为一新报道位点。从重复关联的8个标记位点内共检测出10种优异等位变异。barc28-229bp和barc28-217bp对提高整穗发芽抗性效应最显著,主要分布在地方品种中(如遂宁坨坨麦等),而gwm102-142bp和barc186-199bp效应虽然相对较小,但多分布在推广品种中(如扬麦158等),有利于穗发芽抗性分子育种的直接应用。     

Alleles on the two dwarfing loci on 4B and 4D are main drivers of FHB‐related traits in the Canadian winter wheat population “Vienna” × “25R47”

Fusarium head blight (FHB), leaf rust and stem rust are among the most destructive wheat diseases. High‐yielding, native disease resistance sources are available in North America. The objective of this study was to map loci associated with FHB traits, leaf rust, stem rust and plant height in a “Vienna”/”25R47” population. DArT markers were used to generate a genetic map, and quantitative trait loci (QTL) analysis was performed by evaluating 113 doubled haploid lines across three environments in Ontario, Canada. FHB resistance QTL were identified on chromosomes 4D, 4B, 2D and 7A, while a QTL for leaf and stem rust resistance was identified on chromosome 1B. The dwarfing alleles of both Rht‐B1 and Rht‐D1 were associated with increased FHB index and DON content.     

Detection of molecular markers linked to the durable adult plant stripe rust resistance gene Yr18 in bread wheat (Triticum aestivum L.)

Stripe rust of wheat caused by Puccinia striiformis West. f. sp. tritici presents a serious problem for wheat production worldwide, and identification and deployment of resistance sources to it are key objectives for many wheat breeders. Here we report the detection of simple sequence repeat (SSR) markers linked to the durable adult plant resistance of cv. ‘Otane’, which has conferred this resistance since its release in New Zealand in 1984. A double haploid population from a cross between ‘Otane’ and the susceptible cv. Tiritea’ was visually assessed for adult plant infection types (IT) in the glasshouse and field, and for final disease severity in the field against stripe rust pathotype 106E139A⁺. At least three resistance loci controlled adult plant resistance to stripe rust in this population. Quantitative trait loci (QTL) mapping results revealed that two of these, one on chromosome 7DS corresponds to the durable adult plant resistance gene Yr18 and other on chromosome 5DL were contributed from ‘Otane’; while the remaining one on chromosome 7BL, was contributed from the susceptible ‘Tiritea’. Interval mapping placed the ‘Otane’‐resistant segment near the centromere of chromosome 7DS at a distance of 7 cM from the SSR marker gwm44. The stability of QTL in the two environments is discussed. SSR gwm44 is potentially a candidate marker for identifying the durable resistance gene Yr18 in breeding programmes.     

Barley—Pyrenophora graminea interaction: QTL analysis and gene mapping

Pyrenophora graminea is a seed-borne pathogen and is the causal agent of the barley leaf stripe disease. Our aim is to study the genetic basis of barley resistance to leaf stripe. A qualitatively acting resistance factor has been identified in the cultivar ‘Vada’ and the partial resistance of the cultivar ‘Proctor’ to a P. graminea isolate has been demonstrated to be dominated by a major quantitative trait locus (QTL), mapped on barley chromosome 1. Map colinearity between the leaf stripe ‘Proctor’ resistance QTLs,‘Vada’ resistance to leaf stripe, and other disease resistance loci have been investigated in this work using molecular markers. Moreover, since inoculation of barley rootlets by the fungus had been shown to induce the accumulation of several PR (pathogen-related) mRNA families, seven barley PR genes have been mapped as RFLPs, and one assigned to a chromosome arm via ditelosomic analysis to verify possible map associations with resistance QTLs. This work discusses the genetic relationships between the known leaf stripe resistance loci, resistance loci towards other seed-borne pathogens and defence gene loci.     

Molecular mapping re-locates the Stb2 gene for resistance to Septoria tritici blotch derived from cultivar Veranopolis on wheat chromosome 1BS

Septoria tritici blotch (STB) is one of the most destructive foliar diseases in many of the wheat (Triticum aestivum) growing regions of the world. Gene Stb2, derived from cultivar ‘Veranopolis’, provides effective resistance against STB. In our attempts to refine the map location of this resistance gene we could not confirm a previous report that Stb2 is on wheat chromosome 3BS. Instead, based on characterization of the same doubled-haploid population used for the original mapping derived from a cross between Veranopolis and susceptible line RAC875-2, and linkage analysis of the resistance phenotype to previously mapped SSR loci, we report that Stb2 is located on the short arm of wheat chromosome 1B, flanked by microsatellite loci Xwmc406 and Xbarc008 (with Xwmc230 closely located) at map distances of 6 and 5 cM, respectively. Presence of the markers on chromosome arm 1BS was confirmed by analysis of nullisomic-tetrasomic lines. These three co-dominant markers can be used in wheat breeding programs to facilitate combining Stb2 with genes of interest. Other STB resistance genes, including Stb11, have been reported on wheat chromosome arm 1BS, with locus Xbarc008 as a diagnostic marker. Whether Stb2, Stb11 and the previously identified Stb11-like genes are the same, allelic, or different but closely linked has not been determined. In addition to STB, numerous genes for resistance to many other fungal pathogens have been reported on wheat chromosome arm 1BS, including those for yellow (or stripe) rust, leaf rust and common bunt. The approximate locations for all of these genes were added onto the Stb2 map based on published distances from common markers to provide a rough guide for future wheat improvement.     

南农92R系统白粉病抗源多抗性鉴定及其抗条锈性遗传分析

对南农92R系统白粉病抗源进行了多抗性鉴定,并对其抗条锈性进行了遗传分析。结果表明:4份南农92R系统白粉病抗源,不仅对白粉病多个小种免疫,而且对中国当前优势条锈菌生理小种均表现免疫,其中的92R178和92R137亦对供试3个叶锈菌优势小种均表现高抗至免疫。抗条锈性遗传分析显示92R089, 92R137分别具有一对完全显性的抗条     

普通小麦‘Holdfast’条锈病成株抗性QTL定位

Holdfast是来自英国的小麦品种,多年来一直保持良好的条锈病持久抗性。本研究目的是发掘Holdfast的条锈病成株抗性基因及其紧密连锁的分子标记,为小麦持久抗性品种选育提供材料和方法。利用铭贤169和Holdfast杂交后代重组自交系(recombinant inbred lines, RIL)群体,于2014—2015和2015—2016年度在甘肃甘谷、甘肃中梁和四川成都进行条锈病成株抗性鉴定,并统计最大严重度(maximum disease severity, MDS)。基于小麦660K SNP芯片和BSA(bulkedsegregantanalysis)技术初步确定抗病基因所在的染色体后,将目标区域的SNP标记转化为KASP(KompetitiveallelespecificPCR)标记,检测整个RIL群体,进行基因型分析。最后进行RIL群体条锈病成株抗性的QTL分析,在5AL和7AL染色体上发现了2个成株抗性QTL。5A染色体长臂上1个条锈病成株抗性QTL QYr.gaas-5AL,在所有环境下均存在,可解释6.5%～9.3%的表型变异; QYr.gaas-5AL位于标记Ax-109948955和Ax-108798241之间,连锁距离分别为0.5 cM和1.1 cM。在7A染色体长臂上定位到1个条锈病成株抗性QTL QYr.gaas-7AL,在2015年和2016年甘谷环境中均稳定存在,分别解释6.2%和7.3%的表型变异;QYr.gaas-7AL位于标记Ax-110361069和Ax-108759561之间,连锁距离分别为0.5 cM和0.7 cM。携带QYr.gaas-5AL和QYr.gaas-7AL抗病等位基因家系的MDS显著低于感病等位基因家系的MDS,表明QYr.gaas-5AL和QYr.gaas-7AL可有效降低条锈病严重度,可应用于小麦抗条锈育种。     

Identification and molecular tagging of a stripe rust resistance gene in wheat line P81

Stripe rust, caused by Puccinia striiformis f. sp. tritici (PST), is one of the most devastating diseases in common wheat ( Triticum aestivum L.). With the objective of identifying and tagging a new gene for resistance to stripe rust in wheat line P81, F₁, F₂ and F_2:3 populations from the cross 'Chuanmai 28'/P81 were inoculated with Chinese PST race CYR32 in greenhouse and field trials. P81 carried a single dominant gene for resistance (designated YrP81 ) to CYR32. Tests of allelism showed that YrP81 was different from Yr5 , Yr10 , Yr15 and Yr26 . Simple sequence repeat (SSR) and resistance gene-analogue polymorphism (RGAP) between the parents were used for genotyping the F₂ populations. YrP81 was closely linked to four SSR loci on chromosome 2BS with genetic distances of 18.3 cM ( Xwmc25 ), 1.8 cM ( Xgwm429 ), 4.1 cM ( Xwmc770 ) and 5.3 cM ( Xgwm148 ). Two RGAP markers RGA1 (NLRR/XLRR) and RGA2 (Pto kin4/NLRR-INV2) were also closely linked to YrP81 with genetic distances of 4.7 and 6.3 cM, respectively. The linkage map of YrP81 and molecular markers was established in the order Xwmc25 - RGA2 - RGA1 - Xgwm429 - YrP81 - Xwmc770 - Xgwm148 . Pedigree analysis, response patterns with Chinese PST races and associations with markers suggested that YrP81 is a novel stripe rust resistance gene. The PCR-based microsatellite and RGAP markers identified here could be applied in selection of YrP81 in wheat breeding.     

Effects of environment, disease progress, plant height and heading date on the detection of QTLs for resistance to Fusarium head blight in an European winter wheat cross

In order to characterise quantitative trait loci (QTLs) for Type I and Type II resistance against Fusarium head blight (FHB) in wheat, a population of recombinant inbred lines derived from the cross Cansas (moderately resistant)/Ritmo (susceptible) was evaluated in spray-inoculated field trials over three seasons. Map-based QTL analysis across environments revealed seven QTLs on chromosomes 1BS, 1DS, 3B, 3DL, 5BL, 7BS and 7AL (QFhs.whs-1B, QFhs.whs-1D, QFhs.whs-3B, QFhs.whs-3D, QFhs.whs-5B, QFhs.whs-7A, QFhs.whs-7B) associated with FHB resistance. They accounted for 56% of the phenotypic variance. QFhs.whs-1D primarily appeared to be involved in resistance to fungal penetration, whereas the other QTLs mainly contributed to resistance to fungal spread. FHB resistance was significantly correlated with plant height (PH) and heading date (HD). Including all single environments, corresponding overlaps of QTLs for FHB resistance and QTLs for PH/HD occurred at six loci, among them two consistently detected QTLs, QFhs.whs-5B and QFhs.whs-7A. When significant effects of PH and HD on FHB resistance were eliminated by covariance analysis, a second QTL analysis revealed possible escape mechanisms for the majority of the coincidental loci.     

Identification and mapping of adult‐plant stripe rust resistance in soft red winter wheat cultivar ‘USG 3555’

Little is known about the extent or diversity of resistance in soft red winter wheat (Triticum aestivum L.) to stripe rust, caused by the fungal pathogen Puccinia striiformis f.sp. tritici. The soft red winter (SRW) wheat cultivar ‘USG 3555’ has effective adult‐plant resistance to stripe rust, which was characterized in a population derived from ‘USG 3555’/‘Neuse’. The mapping population consisted of 99 recombinant inbred lines, which were evaluated for stripe rust infection type (IT) and severity to race PST‐100 in field trials in North Carolina in 2010 and 2011. Genome‐wide molecular‐marker screenings with 119 simple sequence repeats and 560 Diversity Arrays Technology (DArT) markers were employed to identify quantitative trait loci (QTL) for stripe rust resistance. QTL on chromosomes 1AS, 4BL and 7D of ‘USG 3555’ explained 12.8, 73.0 and 13.6% of the variation in stripe rust IT, and 13.5, 72.3 and 10.5% of the variation in stripe rust severity, respectively. Use of these and additional diagnostic markers for these QTL will facilitate the introgression of this source of stripe rust resistance into SRW wheat lines via marker‐assisted selection.     

Ph I-induced transfer of leaf and stripe rust-resistance genes from Aegilops triuncialis and Ae. geniculata to bread wheat

Leaf and stripe rusts are severe foliar diseases of bread wheat. Recently, chromosomes 5M^g from the related species Aegilops geniculata that confers resistance to both leaf and stripe rust and 5U^t from Ae. triuncialis conferring resistance to leaf rust have been transferred to bread wheat in the form of disomic DS5M^g(5D) and DS5U^t(5A) chromosome substitution lines. The objective of this study was to shorten the alien segments in these lines using Ph ^I-mediated, induced homoeologous recombination. Putativerecombinants were evaluated for their rust resistance, and by genomic in situ hybridization and microsatellite analyses. One agronomically useful wheat-Ae. geniculata recombinant resistant to leaf and stripe rust was identified that had only a small terminal segment of the 5M^gL arm transferred to the long arm of an unidentified wheat chromosome. This germplasm can be used directly in breeding programs. Only one leaf rust-resistant wheat-Ae. triuncialis recombinant, which consists of most of the complete 5U^t chromosome with a small terminal segment derived from 5AS, was identified. This germplasm will need further chromosome engineering before it can be used in wheat improvement. This revised version was published online in August 2006 with corrections to the Cover Date.