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.     

Common bean breeding for resistance against biotic and abiotic stresses: From classical to MAS breeding

Summary Breeding for resistance to biotic and abiotic stresses of global importance in common bean is reviewed with emphasis on development and application of marker-assisted selection (MAS). The implementation and adoption of MAS in breeding for disease resistance is advanced compared to the implementation of MAS for insect and abiotic stress resistance. Highlighted examples of breeding in common bean using molecular markers reveal the role and success of MAS in gene pyramiding, rapidly deploying resistance genes via marker-assisted backcrossing, enabling simpler detection and selection of resistance genes in absence of the pathogen, and contributing to simplified breeding of complex traits by detection and indirect selection of quantitative trait loci (QTL) with major effects. The current status of MAS in breeding for resistance to angular leaf spot, anthracnose, Bean common mosaic and Bean common mosaic necrosis viruses, Beet curly top virus, Bean golden yellow mosaic virus, common bacterial blight, halo bacterial blight, rust, root rots, and white mold is reviewed in detail. Cumulative mapping of disease resistance traits has revealed new resistance gene clusters while adding to others, and reinforces the co-location of QTL conditioning resistance with specific resistance genes and defense-related genes. Breeding for resistance to insect pests is updated for bean pod weevil (Apion), bruchid seed weevils, leafhopper, thrips, bean fly, and whitefly, including the use of arcelin proteins as selectable markers for resistance to bruchid seed weevils. Breeding for resistance to abiotic stresses concentrates on drought, low soil phosphorus, and improved symbiotic nitrogen fixation. The combination of root growth and morphology traits, phosphorus uptake mechanisms, root acid exudation, and other traits in alleviating phosphorus deficiency, and identification of numerous QTL of relatively minor effect associated with each trait, reveals the complexity to be addressed in breeding for abiotic stress resistance in common bean.     

Evaluation of seedling and adult plant resistance to stem rust in European wheat cultivars

A total of 105 European wheat cultivars were assessed for seedling and adult plant resistance (APR) to stem rust using an array of Australian isolates of Puccinia graminis f. sp. tritici. Twenty-seven cultivars were susceptible at both seedling and adult plant growth stages. Twelve catalogued seedling stem rust resistance genes (Sr7b, Sr8a, Sr8b, Sr9b, Sr9g, Sr11, Sr15, Sr17, Sr29, Sr31, Sr36 and Sr38) were detected in the remaining cultivars, and 13 cultivars carried additional seedling resistance genes that could not be postulated with the isolates used. Low levels of APR to stem rust were found in the cultivars Artaban, Forno, Mec, Mercia, Pandas and Vlada. Although the genetic identity of this APR was not determined, it was clear that the only designated stem rust APR gene Sr2 was not present in any of the cultivars tested based on the absence of the linked traits seedling chlorosis and pseudo black chaff. One of these cultivars, Forno, is believed to carry the leaf rust APR gene Lr34, previously reported to be associated with improved resistance to stem rust. A detailed genetic characterisation of the APRs in these cultivars will be needed to understand their modes of inheritance and relationships with catalogued stem rust resistance genes. Such knowledge may help in developing cultivars with effective gene combinations that confer higher levels of protection.     

Identification of QTL associated with durable adult plant resistance to stem rust race Ug99 in wheat cultivar ‘Pavon 76’

Stem rust of wheat, caused by Puccinia graminis f. sp. tritici, was under control worldwide for over 30 years by utilizing genetic resistance. The emergence of stem rust in 1998 in eastern Africa in form of race Ug99 and its evolving variants with virulence to many resistance genes were recognized as potential threats to wheat production. In this study we identified genomic regions contributing to putatively durable, adult plant resistance (APR) to wheat stem rust. A recombinant inbred line (RIL) population of 298 lines was previously developed at CIMMYT from a cross between ‘Avocet S’ and ‘Pavon 76’. Pavon 76 has been described to carry APR to stem rust. Avocet S carries the race-specific resistance gene Sr26. A subset of RILs without Sr26 segregated for APR to stem rust race Ug99 when evaluated in Kenya for three years. Single year and joint year analysis by inclusive composite interval mapping using 450 DArT markers identified five quantitative trait loci (QTL) that contributed to the resistance of wheat to stem rust race Ug99. Three of these, including QSr.cim-3B, which probably represents the Sr2 gene, were contributed by Pavon 76 whereas the remaining two QTL were contributed by Avocet S. QSr.cim-3B, or putatively Sr2, on chromosome arm 3BS explained 32 % of the phenotypic variation while the additional QTL in Pavon contributed 24 and 20 %, respectively. Two QTL from Avocet S explained 8 and 6 % of phenotypic variance, respectively. A combination of APR QTL from the two parents resulted in transgressive segregants expressing higher levels of resistance than Pavon 76. Our results indicate that it is possible to accumulate several minor resistance genes each with a small to intermediate effect resulting in a variety that exhibits negligible disease levels even under high stem rust pressure.     

Race non-specific resistance to rust diseases in CIMMYT spring wheats

Rust diseases continue to cause significant losses to wheat production worldwide. Although the life of effective race-specific resistance genes can be prolonged by using gene combinations, an alternative approach is to deploy varieties that posses adult plant resistance (APR) based on combinations of minor, slow rusting genes. When present alone, APR genes do not confer adequate resistance especially under high disease pressure; however, combinations of 4?C5 such genes usually result in ??near-immunity?? or a high level of resistance. Although high diversity for APR occurs for all three rusts in improved germplasm, relatively few genes are characterized in detail. Breeding for APR to leaf rust and stripe rust in CIMMYT spring wheats was initiated in the early 1970s by crossing slow rusting parents that lacked effective race-specific resistance genes to prevalent pathogen populations and selecting plants in segregating populations under high disease pressure in field nurseries. Consequently most of the wheat germplasm distributed worldwide now possesses near-immunity or adequate levels of resistance. Some semidwarf wheats such as Kingbird, Pavon 76, Kiritati and Parula show high levels of APR to stem rust race Ug99 and its derivatives based on the Sr2-complex, or a combination of Sr2 with other uncharacterized slow rusting genes. These parents are being utilized in our crossing program and a Mexico-Kenya shuttle breeding scheme is used for selecting resistance to Ug99. High frequencies of lines with near-immunity to moderate levels of resistance are now emerging from these activities. After further yield trials and quality assessments these lines will be distributed internationally through the CIMMYT nursery system.     

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。     

Seedling resistance to stem rust race Ug99 and marker analysis for Sr2, Sr24 and Sr31 in South African wheat cultivars and lines

The appearance and spread of races of Puccinia graminis f. sp. tritici with virulence for the Sr31 resistance gene has renewed interest in breeding for durable resistance to stem rust of wheat. Since the occurrence of stem rust has been low in South Africa until the detection of race TTKSF in 2000, breeding for resistance to this disease has not been a primary objective. The aim of this study was to test bread wheat cultivars and lines at the seedling stage for their infection response to stem rust, thus determining their level of resistance or vulnerability. A collection of 65 bread wheat entries was tested with one USA race, two Eastern African races, and three South African races of P. graminis f. sp. tritici. The Eastern African and South African races all belong to the Ug99 lineage. The cultivars Duzi, Caledon, Elands, PAN 3364, PAN 3191, SST 047, SST 399, and Steenbras produced resistant infection types (IT < 3) to all races. The molecular marker Sr24#50 indicated the presence of Sr24 in 12 entries. In cultivars resistant to TTTTF, TTKSF, and TTKSP but susceptible to TTKSK and PTKST, the iag95 DNA marker indicated the presence of Sr31 in five wheat lines. Using the cleaved amplified polymorphic sequence marker csSr2, Sr2 was detected in PAN 3377, Inia, and Steenbras. Few South African wheat cultivars appear to have a broad-based resistance to stem rust, as 88% of the entries were susceptible as seedlings to at least one of the races tested. Diversification of resistance sources and more directed breeding for stem rust resistance are needed in South Africa.     

‘CPAN 1842’: a new source of adult plant leaf rust resistance in bread wheat

There is worldwide interest in adult plant resistance (APR) because of greater durability of APR to the cereal rusts. Peruvian bread wheat genotype ‘CPAN (Coordinated Project Accession Number) 1842’ (LM 50–53) has shown leaf rust resistance in disease screening nurseries since its introduction in 1977. However, it is susceptible at the seedling stage to several Puccinia triticina (Pt) pathotypes including the widely prevalent 77‐5 (121R63‐1) that infects bread wheat. Inheritance studies showed that CPAN 1842 carried a dominant gene for APR to pathotype 77‐5, which was different from Lr12, Lr13, Lr22a, Lr34, Lr35, Lr37, Lr46, Lr48, Lr49 and Lr68, based on the tests of allelism; and from Lr67, based on genotyping with the closely linked SSR marker cfd71. This gene should also be different from Lr22b as the latter is totally ineffective against pathotype 77‐5. CPAN 1842 therefore appears to be a new promising source of leaf rust resistance. Also having resistance to stem rust and stripe rust, this line can contribute to breeding for multiple rust resistances in wheat.     

Genetic Diversity for Adult Plant Resistance to Leaf Rust (Puccinia recondita) in Near-Isogenic Lines and in Indian Wheats

Variation for adult plant resistance in near-isogenic wheat lines carrying Lrl4b, Lrl4ab and Lr30 in a ‘Thatcher’ background indicated the possible presence of novel adult plant resistance genes effective against the Indian leaf rust population. Sixty-one wheats released for cultivation in India were grown in isolated nurseries. Each nursery was separately inoculated with one of four leaf rust pathotypes which had been selected to aid identification of resistance effective only in the adult plant stage. Seven distinct response groups were recognised and a minimum of six sources of adult plant resistance were postulated. In a group of 14 wheats, resistance was explained on the basis of the seedling response genes that were identified. Similar results for two years with pathotype 77-1 gave support to the reliability of field tests. Adult plant resistance (APR) sources were either race-specific or effective against all pathotypes used. Seedlings of cultivars with APR showed susceptible reactions. The possible presence of Lr34 in Indian wheats and its role in durable leaf rust resistance are discussed.     

The role of Lr34 in imparting durable resistance to wheat leaf rust through gene interaction

Summary The leaf rust responses of wheat lines carrying the complementary genes Lr27 and Lr31 and the same genes in a Chinese Spring background which contains Lr34, indicate that Lr34 interacts with the complementary genes to give enhanced levels of field resistance to leaf rust. Lr34, particularly in combination with other genes, is considered to be an important gene for imparting a high degree of durable resistance to leaf rust. Its similarity to Sr2, an adult plant gene for resistance to stem rust and its association with adult plant resistances to stem and stripe rusts are discussed.     

Rapid identification of a major effect QTL conferring adult plant resistance to stripe rust in wheat cultivar Yaco“S”

Stripe rust is a devastating disease in common wheat (Triticum aestivum) worldwide. Growing cultivars with adult-plant resistance (APR) is an environmental friendly approach that provides long-term protection to wheat from this disease. Wheat cultivar Yaco“S” showed a high level of APR to stripe rust in the field from 2008 to 2014. The objective of this study was to detect the major quantitative trait loci (QTL) for APR to stripe rust in Yaco“S”. One hundred and eighty-four F_2:3 lines were developed from a cross between Yaco“S” and susceptible cultivar Mingxian169. Illumina 90K and 660K single nucleotide polymorphism (SNP) chips were implemented to bulked pools and their parents to identify SNPs associated with the major QTL. A high-density linkage map was constructed using simple sequence repeat (SSR) and SNP markers. Inclusive composite interval mapping detected a major effect QTL Qyryac.nwafu-2BS conferring stable resistance to stripe rust in all tested environments. Qyryac.nwafu-2BS were mapped to a 1.3 cm interval and explained 17.3–51.9% of the phenotypic variation. Compared with stripe rust resistance genes previously mapped to chromosome 2B, Qyryac.nwafu-2BS is likely a new APR gene to stripe rust. Combining SNP iSelect assay and kompetitive allele specific PCR technology, we found that the APR gene could be rapidly and accurately mapped and it is useful for improving stripe rust resistance in wheat breeding.     

Novel gene for adult plant resistance to Puccinia recondita in the wheat cultivar'Arjun'

Inheritance of resistance in the wheat cultivar‘Arjun’(HD 2009) against leaf rust pathotype 77–1 revealed that its durable resistance is attributable to a novel dominant adult plant resistance (APR) gene. Lr13, another gene reported in the cultivar played no role. This new gene is established as different from Lr34, the only effective APR gene from Triticum aestivum known for durability.     

利用cDNA-AFLP技术分析小麦成株抗条锈性差异基因表达特征

采用cDNA-AFLP技术,对成株抗条锈小麦品种兴资9104在成株期受条锈菌生理小种CY32侵染后5 d内9个时间点的基因表达谱进行了分析。共筛选64对引物,产生32 320个转录本(TDF);用37对引物检测到2 201个(6.81%)差异TDF,其中926个TDF诱导表达,1 275个下调表达。经大规模克隆、测序分析,最终获得330个差异TDF,聚类分析得到259个EST (unigenes),命名为aTaPST1至aTaPST259 (GenBank注册号：FL645754~FL646011和FL646262)。经BLASTX比对和功能分类分析,其中96条EST(37.07%)未找到同源性匹配,68条(26.25%)与未知功能蛋白同源性较高;其余95条ESTs主要涉及能量(11.20%)、基础代谢(4.63%)、转录调控(3.86%)、抗病与防御(3.86%)、蛋白质运输和储存(3.09%)、蛋白质合成和细胞生长(各2.32%)、以及信号转导(1.54%)等。选取抗病与防御、转录调控及信号转导类等相关的6个差异基因,qRT-PCR分析结果显示其表达模式符合cDNA-AFLP表达谱。小麦成株抗条锈性分子机制涉及植物多方面生理生化反应,包括抗病与防御、转录调控、蛋白质代谢、信号转导、以及非生物胁迫等多种途径相关基因的协同控制。     

Evaluation of seedling and adult plant resistance to leaf rust in European wheat cultivars

Summary A set of 105 European wheat cultivars, comprising 68 cultivars with known seedling resistance genes and 37 cultivars that had not been tested previously, was tested for resistance to selected Australian pathotypes of P. triticina in seedling greenhouse tests and adult plant field tests. Only 4% of the cultivars were susceptible at all growth stages. Twelve cultivars lacked detectable seedling resistance to leaf rust, and among the remaining cultivars, 10 designated genes were present either singly or in combination. Lr13 was the most frequently detected gene, present in 67 cultivars, followed by the rye-derived gene Lr26, present in 19 cultivars. Other genes present were Lr1, Lr3a, Lr3ka, Lr10, Lr14a, Lr17b, Lr20 and Lr37. There was evidence for unidentified seedling resistance in addition to known resistance genes in 11 cultivars. Field tests with known pathotypes of P. triticina demonstrated that 57% of the cultivars carried adult plant resistance (APR) to P. triticina. The genetic identity of the APR is largely unknown. Genetic studies on selected cultivars with unidentified seedling resistances as well as all of those identified to carry APR are required to determine the number and inheritance of the genes involved, to determine their relationships with previously designated rust resistance genes, and to assess their potential value in breeding for resistance to leaf rust.     

Development of a PCR assay and marker-assisted transfer of leaf rust resistance gene <Emphasis Type="Italic">Lr58</Emphasis> into adapted winter wheats

Leaf rust resistance gene Lr58 derived from Aegilops triuncialis L. was transferred to the hard red winter wheat (HRWW) cultivars Jagger and Overley by standard backcrossing and marker-assisted selection (MAS). A co-dominant PCR-based sequence tagged site (STS) marker was developed based on the sequence information of the RFLP marker (XksuH16) diagnostically detecting the alien segment in T2BS·2BL-2^tL(0.95). STS marker Xncw-Lr58-1 was used to select backcross F₁ plants with rust resistance. The co-dominant marker polymorphism detected by primer pair NCW-Lr58-1 efficiently identified the homozygous BC₃F₂ plants with rust resistance gene Lr58. The STS marker Xncw-Lr58-1 showed consistent diagnostic polymorphism between the resistant source and the wheat cultivars selected by the US Wheat Coordinated Agricultural Project. The utility and compatibility of the STS marker in MAS programs involving robust genotyping platforms was demonstrated in both agarose-based and capillary-based platforms. Screening backcross derivatives carrying Lr58 with various rust races at seedling stage suggested the transferred rust resistance in adapted winter wheats is stable in both cultivar backgrounds. Lr58 in adapted winter wheat backgrounds could be used in combination with other resistance genes in wheat rust resistance breeding.     

Unveilingsources of stripe rust resistance in diverse wheat (<Emphasis Type="Italic">Triticum Aestivum</Emphasis> L.) germplasm using narrow down methodology: a proof of concept

Stripe rust of wheat caused by the fungal pathogen is a destructive foliar disease of wheat. Thus, it is crucial step to characterize the resistant germplasm for stripe rust in a diverse germplasm pool for their ultimate utilization in efficient crop rust resistance breeding. In the present study, we followed two pronged strategies involving integrated phenotypic and molecular characterization of 440 diverse wheat germplasm lines for rust resistance. The germplasm panel was extensively evaluated in field epiphytotic conditions during two consecutive years. After rigorous screening, 72 accessions were successfully revealed as resistant to moderately resistant to stripe rust. Subsequently, entries were then evaluated for their field agronomicperformances, considering prerequisites for serving as a donor germplasm,particularly for yield and 33 potential rust-resistant accessions were identified. Furthermore, to detect the sources of resistance, accessions were molecular characterized for potential race-specific resistance genes Yr5, Yr10,Yr15, and effective adult plant resistance (APR) gene Lr34/Yr18/pm38. We identified the 22 accessions possessing one or more single resistance genes and two accessions were observed with at least three of them. Moreover, Lr34/Yr18/pm38 was determined to confer resistance when observed along with any of the race-specific genes. Thus, the study not only provides proof of concept methodology to identify candidate resistant sources from large germplasm collections but simultaneouslyconfirmed the contribution of combining race-specific andnon-specific APR genes. The finding could further assist in the potential deployment of resistant genes directly into the stripe rust breeding program by involving marker-assisted approaches.     

Wheat breeding assisted by markers: CIMMYT’s experience

Significant progress has been made in the characterization of loci controlling traits of importance using molecular markers. A number of markers are currently available in wheat for genes of interest to the breeders. Markers can be used to better characterize parental material, thereby improving the efficiency and effectiveness of parental selection for crossing and to track genes in segregating progenies through the selection process. Although a number of breeding programs are using molecular markers at modest levels, the costs associated with marker assisted selection (MAS) are frequently cited as the main constraint to their wide-spread use by plant breeders. However, this is likely to change when user-friendly, high-throughput, automated marker technologies based on single nucleotide polymorphisms become available. These evolving technologies will increase the number of available markers, and will improve the efficiency, throughput, and cost effectiveness of MAS, thereby making it more attractive and affordable to many breeding programs. This article examines the extent to which molecular markers have been used at the International Maize and Wheat Improvement Center (CIMMYT) in applied wheat breeding and reviews the limited publicly available information on MAS from other wheat breeding programs. As markers are currently available for relatively few traits, we believe that MAS must be integrated with ongoing conventional breeding to maximize its impact. When used in tandem with phenotypic selection, MAS will improve response to selection for certain traits, thereby increasing rates of genetic progress.     

Specific resistance to leaf rust expressed at the seedling stage in cultivars grown in France from 1983 to 2007

Host resistance is the most economical means to reduce yield losses caused by wheat leaf rust. Knowledge of the effective specific resistance genes is a prerequisite for analysis of the non-specific components of resistance, assumed to be more durable than specific resistance. Lr genes were inferred from seedling response phenotype of 275 wheat cultivars and 21 standard isolates of Puccinia triticina. Enough cultivars were selected for analysis so that findings would account for at least two-thirds of the French agricultural land dedicated to wheat from 1983 to 2007. In this paper, genes Lr13, Lr37, Lr10, Lr14a, Lr3, Lr26, Lr1, Lr24, Lr20 are postulated, alone or in combinations, in, respectively, 67%, 45%, 34%, 20%, 8%, 7%, 6%, 1%, and 1% of the cultivars. Forty five phenotypic arrays were found, the most frequent being (Lr10, Lr13, Lr37) and (Lr13) in 45 and 37 cultivars, respectively. Over the period, the combinations became increasingly complex. Isolates with virulence corresponding to most of the Lr gene combinations were identified in the pathogen population, except for combinations involving Lr24 and some unidentified genes. These findings will help breeders and extension service staff (Arvalis) in diversifying sources of resistance to wheat leaf rust. This information is also crucial for research programs aiming, on the one hand, to identify sources of quantitative resistance, and, on the other hand, to quantify selection pressure exerted on pathogen populations.     

Molecular mapping of powdery mildew resistance genes in wheat: A review

Powdery mildew, caused by Blumeria graminis f. sp. tritici (syn. Erysiphe graminis f. sp. tritici), is one of the most important diseases of common wheat (Triticum aestivum L.) worldwide. Molecular mapping and cloning of genes for resistance to powdery mildew in hexaploid wheat will facilitate the study of molecular mechanisms underlying resistance to powdery mildew diseases and help understand the structure and function of powdery mildew resistance genes, and permit marker-assisted selection in breeding programs. So far, 48 genes/alleles for resistance to powdery mildew at 32 loci have been identified and located on 16 different chromosomes, of which 21 resistance genes/alleles have been tagged by restriction fragment length polymorphisms (RFLPs), random-amplified polymorphic DNAs (RAPDs), amplified fragment length polymorphisms (AFLPs), sequence characterized amplified regions (SCARs), sequence-tagged sites (STS) or simple sequence repeats (SSRs). Several quantitative trait loci (QTLs) for adult plant resistance (APR) to powdery mildew have been associated with molecular markers. The detailed information on chromosomal location and molecular mapping of these genes has been reviewed. Isolation of powdery mildew resistance genes and development of valid molecular markers for pyramiding resistance genes in breeding programs is also discussed.     

The use of wild relatives in crop improvement: a survey of developments over the last 20 years

Hypersensitive, race specific genes primarily have been deployed to control powdery mildew (Blumeria graminis (DC) EO Speer f. sp. tritici) in wheat (Triticum aestivum L.); however, recent efforts have shifted to breeding for more durable resistance. Previously, three quantitative trait loci (QTL) for adult plant resistance (APR) to powdery mildew in the winter wheat cultivar Massey were identified in a Becker/Massey (BM) F _2:3 population. Fourteen new simple sequence repeat (SSR) markers were added to the pre-existing BM F _2:3 linkage maps near the QTL for APR on chromosomes 1BL (QPm.vt-1BL), 2AL (QPm.vt-2AL), and 2BL (QPm.vt-2BL). Genetic linkage maps comprised of 17 previously and newly mapped SSRs from the BM population on chromosomes 1BL, 2AL, and 2BL were constructed in a USG 3209/Jaypee (UJ) F _6:7 recombinant inbred line (RIL) confirmation population, wherein the APR resistance of USG 3209 was derived from Massey. Interval mapping analysis of mildew severity data collected in 2002 (F _5:6) and 2003 (F _6:7) field experiments with marker genotypic data obtained in 2003 (F _6:7) confirmed the presence of the three QTL governing APR to powdery mildew in the UJ RILs. The QTL QPm.vt-1BL, QPm.vt-2AL, and QPm.vt-2BL explained 12–13, 59–69, and 22–48% of the phenotypic variance for powdery mildew severity in the UJ confirmation populations, respectively, in two field experiments. The current study verified that the elite wheat cultivar USG 3209 possesses the same QTL for APR as its parent Massey.