Genetic diversity of resistance genes controlling fusarium head blight with simple sequence repeat markers in thirty-six wheat accessions from east asian origin

Summary Fusarium head blight (FHB) is a serious disease of wheat worldwide that may cause substantial yield and quality losses. Breeding for FHB-resistant cultivars is the most cost-effective approach to control FHB. The objective of the present study was to determine the relationship of resistance between new resistant sources and Sumai 3 using five simple sequence repeat (SSR) markers closely linked to the major QTL for FHB resistance on chromosome arms 3BS and 6BS. All five SSR markers were highly polymorphic between Sumai 3 (and its derivatives) and susceptible Canadian wheat lines. Most of the Sumai 3-derived Chinese wheat accessions and three Canadian FHB-resistant lines had all the Sumai 3 SSR marker alleles on chromosome arms 3BS and 6BS. The Chinese landrace Wangshuibai and two Japanese accessions Nobeokabozu and Nyu Bai had the same banding patterns as Sumai 3 for all five SSR marker alleles, and another Chinese landrace Fangshanmai had three of the five SSR markers in common with Sumai 3, and therefore most likely carries the same QTL as Sumai 3 on 3BS and 6BS. The Brazilian cultivar Frontana had no alleles in common with Sumai 3 on either QTL, and the Chinese landrace Hongheshang had only one of the five SSR markers in common with Sumai 3, therefore likely carrying resistance genes different from Sumai 3. The Italian cultivar Funo is not the donor of either the 3BS QTL or 6BS QTL. All five SSR seem to be effective candidates for marker-assisted selection to increase the level of resistance to FHB in wheat breeding programs.     

小麦纹枯病抗源的遗传多样性及抗性基因位点SSR标记分析

为揭示小麦纹枯病抗源的遗传多样性,发掘优异的抗性种质,利用沟带接种法对前期筛选出的88份抗性种质进行了3年田间抗性鉴定,鉴定出抗或中抗纹枯病的小麦种质32份。利用分布于全基因组的SSR标记对这些抗源进行了遗传多样性分析,59个SSR标记共检测到308个等位变异,每个标记可以检测到2~13个等位基因,平均5.2个;多态性信息含量(PIC)的变异范围为0.12~0.89,平均为0.61,表明材料的遗传丰富度较高。根据聚类分析和主成分(PCA)分析,32份小麦纹枯病抗源按照遗传相似系数可划分为2个组群,国外引进品种和国内改良品种聚为一类,国内农家品种聚为一类,并且与地理分布特征相符。利用与纹枯病抗性QTL紧密连锁的14个SSR标记对32份抗源进行基因型分析,发现与抗性QTL连锁的2BS上的Xwmc154和7DS上的Xbarc126普遍存在,可用于分子标记辅助选择。在武农148、陕983、陕农78、Coker 983、H-Line、Mason和Compair中仅检测到一个已报道的抗病QTL,而在Tyalt中没有检测到已知抗病QTL,这些材料有可能携带新的纹枯病抗性基因/QTL,可以在育种中加以利用。     

New durum wheat with Hessian fly resistance from Triticum araraticum and T. carthlicum in Morocco

Hessian fly is an important pest of wheat on the North American continent and the temperate Mediterranean drylands. Yield losses caused by this insect in Morocco are the heaviest in the Mediterranean region and are estimated to be 36% on average. Genetic resistance to Mediterranean Hessian fly biotypes has not been found in durum wheat, although large numbers of durum accessions were screened. Genes for resistance were found in common wheat; some of which are transferable to durum. However, there is a need to broaden the genetic base for resistance in durum wheat. The objective of this work was to introgress resistance from selected Triticum araraticum and T. carthlicum accessions using multiple backcross methodology. The experimental recipient durum wheat included numerous adapted and high‐yielding lines. Testing for Hessian fly resistance under controlled conditions and field yield data showed that this programme yields Hessian fly‐resistant durum lines with good yields and adaptation.     

Genome-wide association study reveals loci associated with seed longevity in common wheat (Triticum aestivum L.)

Seed longevity could significantly determine seed regeneration cycle and greatly affect wheat production. With the 90 K chip assays, a genome-wide association study was performed to identify seed longevity-related markers and loci in common wheat. Seed germination ratios (GR) under artificially ageing of 166 wheat accessions across three environments were evaluated to assess seed longevity. Totally, 23 longevity-related loci were identified in the study, explaining 6.7%–11.4% of the phenotypic variations. Of these, QlgGR.cas-1A and QlgGR.cas-2B.2 were deemed as stable loci associated with wheat seed longevity. Fifteen loci were found overlapped with known quantitative trait loci or genes. Besides, QlgGR.cas-1A, QlgGR.cas-2B.2, QlgGR.cas-3D.1, QlgGR.cas-3D.2, QlgGR.cas-4A.2, QlgGR.cas-5A.1, QlgGR.cas-5A.2 and QlgGR.cas-6A.1 were colocated with seed dormancy-related loci. Significant additive effects were obtained for seed longevity by pyramiding favourable alleles. Several candidate genes were found involved in signal transduction and stress resistance pathways by sequencing analysis of significantly longevity-related molecular markers. These results might provide new sights into the genetic architecture of seed longevity.     

Evaluation of a collection of wild wheat relative Aegilops geniculata Roth and identification of potential sources for useful traits

A collection comprising 157 Aegilops geniculata accessionsoriginating from different ecogeographical regions was established atENSA-INRA, Montpellier. The accessions were studied for physiologicaltraits related to drought and heat stress and screened for resistance tobarley yellow dwarf virus (BYDV) and rusts. Some accessions were alsotested for resistance to Hessian fly and cereal cyst nematodes (CCN). The study allowed to distinguish different adaptive strategies to theclimatic constraints encountered by Aegilops populations in theirregion of origin. They led to significant differences in biomass and grainproduction and should be taken into account in the utilisation of Ae.geniculata germplasm in wheat breeding programs. Two accessions withresistance to BYDV were found. Both originated from South of France. Theinterest of Ae. geniculata as a source of rust resistance was confirmedand accessions with resistance to the three rusts were identified. Highresistance against populations of Heterodera avenae and H.latipons was found in accessions from Spain, Bulgaria, Jordan and Tunisia.Sources of resistance to Hessian fly were also identified.     

Molecular mapping determines that Hessian fly resistance gene H9 is located on chromosome 1A of wheat

Hessian fly [Mayetiola destructor (Say)] is one of the major insect pests of wheat (Triticum aestivum L.) worldwide. Hessian fly resistance gene H9 was previously reported to condition resistance to Hessian fly biotype L that is prevalent in many wheat‐growing areas of eastern USA and an RAPD marker, OPO05₁₀₀₀, linked to H9 in wheat was developed using wheat near‐isogenic lines (NILs). However, marker‐assisted selection (MAS) with RAPD markers is not always feasible. One of the objectives in this study was to convert an RAPD marker linked to the gene H9 into a sequence characterized amplified region (SCAR) marker to facilitate MAS and to map H9 in the wheat genome. The RAPD fragment from OPO05₁₀₀₀ was cloned, sequenced, and converted into a SCAR marker SOPO05₉₀₉, whose linkage relationship with H9 was subsequently confirmed in two F₂ populations segregating for H9. Linkage analysis identified one sequence tagged site (STS) marker, STS‐Pm3, and the eight microsatellite markers Xbarc263, Xcfa2153, Xpsp2999, Xgwm136, Xgdm33, Xcnl76, Xcnl117 and Xwmc24 near the H9 locus on the distal region of the short arm of chromosome 1A, contrary to the previously reported location of H9 on chromosome 5A. Locus Xbarc263 was 1.2 cM distal to H9, which itself was 1.7 cM proximal to loci Xcfa2153, Xpsp2999 and Xgwm136. The loci Xgwm136, Xcfa2153 and SOPO05₉₀₉ were shown to be specific to H9 and not diagnostic to several other Hessian fly resistance genes, and therefore should be useful for pyramiding H9 with other Hessian fly resistance genes in a single genotype.     

应用SSR分子标记分析国外种质对我国小麦品种的遗传贡献

利用363对SSR标记分析了在我国小麦生产和育种中发挥了重要作用的11份国外引进品种和33份选育品种的遗传组成,旨在揭示国外种质对我国小麦品种改良的遗传贡献,指导种质资源引进和利用。国外种质包含了选育品种所发现等位变异的76.3%。与不同时期小麦品种等位基因多样性比较发现,国外种质的平均等位变异数最多(3.92),20世纪60年代(2.86)和70年代(3.01)基本一致,80年代有所升高(3.46)。品种间遗传距离比较与品种等位基因多样性结果相吻合。比较引进和选育品种在SSR位点的等位变异频率变化,发现至少在33个SSR位点,国外种质等位变异在我国小麦育种中被优先选择(该等位变异在引进和选育品种的分布频率均高于70%),其中一些位点已知与产量、生育期和抗病等性状密切相关。表明引进品种在以上基因组区域对我国小麦品种具有非常高的遗传贡献。     

应用SSR分子标记分析国外种质对我国小麦品种的遗传贡献

利用363对SSR标记分析了在我国小麦生产和育种中发挥了重要作用的11份国外引进品种和33份选育品种的遗传组成,旨在揭示国外种质对我国小麦品种改良的遗传贡献,指导种质资源引进和利用。国外种质包含了选育品种所发现等位变异的76.3%。与不同时期小麦品种等位基因多样性比较发现,国外种质的平均等位变异数最多(3.92),20世纪60年代(2.86)和70年代(3.01)基本一致,80年代有所升高(3.46)。品种间遗传距离比较与品种等位基因多样性结果相吻合。比较引进和选育品种在SSR位点的等位变异频率变化,发现至少在33个SSR位点,国外种质等位变异在我国小麦育种中被优先选择(该等位变异在引进和选育品种的分布频率均高于70%),其中一些位点已知与产量、生育期和抗病等性状密切相关。表明引进品种在以上基因组区域对我国小麦品种具有非常高的遗传贡献。     

大豆引进种质抗胞囊线虫病、抗花叶病毒病和耐盐基因型鉴定及优异等位基因聚合种质筛选

我国从美国、俄罗斯、日本等26个国家或地区共引进大豆种质3218份, 仅对部分种质进行了大豆胞囊线虫病(Soybean cyst nematode, SCN)、大豆花叶病毒病(Soybean mosaic virus, SMV)和盐敏感性的抗性鉴定, 但基因型的系统分析尚未见报道。本研究针对大豆抗胞囊线虫病3个基因(rhg1、Rhg4、SCN3-11)和耐盐基因(GmSALT3)开发KASP标记5个, 结合与大豆花叶病毒抗性相关的1个SCAR标记(SCN11), 对1489份大豆引进种质进行基因型鉴定。结果表明, 具有优异等位基因的种质共1084份; 携带3个位点优异等位基因的种质19份, 包括抗胞囊线虫病3个位点(rhg1、Rhg4、SCN3-11)叠加(Peking型)种质3份, 聚合抗胞囊线虫病基因和抗花叶病毒病标记7份, 聚合抗胞囊线虫病和耐盐基因2份, 聚合抗胞囊线虫病、抗花叶病毒病和耐盐基因7份; 携带4个位点优异等位基因的种质9份, 包括聚合抗胞囊线虫病基因和抗花叶病毒病标记6份, 聚合抗胞囊线虫病和耐盐基因2份, 聚合抗胞囊线虫病、抗花叶病毒病和耐盐7份; 携带5个位点优异等位基因8份, 聚合了抗胞囊线虫病、抗花叶病毒病和耐盐优异等位变异。在这些携带优异等位变异的种质中, 44份已由前人证明具有相应的抗性。携带3个或3个以上优异等位基因的36份种质中, 有52.78%种质的一种或两种特性已被报道。在不携带抗性优异等位变异的种质中, 93份已证明有耐盐性或对SMV3号株系抗性, 这些种质可能存在新的抗性(等位)基因。本研究利用高通量分子标记筛选出的携带抗病、抗逆优异等位基因的种质为我国大豆资源表型鉴定、抗源的快速筛选及利用提供理论依据和新思路。     

Exploring wheat landraces for rust resistance using a single marker scan

Marker-trait associations identified in diverse germplasm can be exploited in crop improvement programs. An attempt to establish such associations was made by evaluating 205 wheat landraces for stripe rust, leaf rust and stem rust responses in the field over three crop seasons. Diversity arrays technology was used to genotype the landraces and associations were identified using a single-marker scan. Sixty-eight markers were significantly associated with rust resistance. Several significantly associated loci coincided with the presence of known major genes or QTL for rust resistance. In contrast, many marker-rust response associations identified in this analysis for each of the three rust diseases uncovered new loci. Dual associations; stripe rust-leaf rust (1AL, 2BS, 2BL, 3DL, 5BS, 6BS and 7DL), leaf rust-stem rust (5BL) and stripe rust-stem rust (4BL and 6AS) resistance were also observed. These associations could enable a cost-effective targeted mapping of dual rust resistance. Some marker-trait associations identified in this study have been validated through genetic analyses and formal naming of resistance loci.     

Molecular mapping of partial resistance to powdery mildew in winter wheat cultivar Folke

The Swedish winter wheat (Triticum aestivum L.) cultivar Folke has a long record of partial and race non-specific resistance to powdery mildew (caused by Blumeria graminis f. sp. tritici) in the field. The aim of the present study was to map the main genetic factors behind the partial resistance in Folke and identify molecular markers for use in marker-assisted selection. A population of 130 recombinant inbred lines was developed from a cross between Folke and the moderately susceptible spring wheat line T2038. The population was tested for powdery mildew resistance over two years at two locations in Norway and genotyped with DArT and SSR markers. Composite interval mapping detected a total of eight quantitative trait loci (QTL) for powdery mildew resistance; six with resistance from Folke on 2BS, 2DL, 5AL, 5BS and 6BS and two with resistance from T2038 on 5BS and 7AL. None of the loci with resistance from Folke mapped to chromosomal regions with known race-specific resistance genes, which confirmed the race non-specific nature of the resistance in this cultivar. The molecular markers linked to the reported QTL will be useful as a tool for selecting partial and potentially durable resistance to powdery mildew based on the resistance in Folke.     

水稻纹枯病抗性关联分析及抗性等位变异发掘

采用苗期微室接种鉴定法,用144个分布于水稻全基因组的多态性标记,利用TASSEL软件GLM (Q)、MLM (Q+K)和MLM (PCA+K) 3种模型对456份水稻材料组成的自然群体进行纹枯病抗性关联分析。结果发现,有13个标记位点至少在两种模型中均被检测到与纹枯病抗性显著关联,单个位点可解释表型变异的1.84%~8.42%;其中10个标记位点位于以往报道的连锁定位的抗纹枯病QTL附近,3个标记位点(RM1036、RM5371和RM7585)是未曾报道的新的抗病相关位点。抗性等位变异RM7585-150对纹枯病发病病级减效效应最大;有259份材料携带抗性等位变异RM5371-129,占供试材料总数的56.8%,只有26份材料携带抗性等位变异RM1036-82,占供试材料总数的5.7%。水稻纹枯病发病病级与其含有的抗性等位变异数量呈极显著的负相关。本研究结果将为水稻抗纹枯病分子标记辅助育种提供理论依据。     

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。     

利用关联分析发掘小麦自然群体旗叶叶绿素含量的优异等位变异

为揭示小麦自然群体干旱胁迫条件下旗叶叶绿素含量的变化, 筛选相关标记的优异等位变异, 以262份小麦种质资源组成的自然群体为材料, 分别种植在北京的2个试验地点, 均设雨养和灌溉处理, 于开花期和灌浆期检测旗叶叶绿素含量。以分布于21条染色体的169个SSR标记检测所有材料的基因型, 利用STRUCTURE 2.3.2软件分析群体结构, 用TASSEL软件的MLM (mixed linear model)方法对小麦自然群体的旗叶叶绿素含量进行关联分析。在此基础上, 将携带某等位变异的所有材料表型均值与携带无效等位基因(null allele)材料表型均值比较, 估计等位变异的表型效应, 鉴别优异等位变异。共检测到2048个等位变异, 每位点2~37个等位变异, 平均12个。每位点的标记多态性信息量(PIC)为0.008~0.936, 平均0.628。在22个标记位点共检测出40个(次)与旗叶叶绿素含量极显著的关联, 其中11个标记位点有2次以上的关联, Xwmc419-1B和Xgwm501-2B分别有3次关联。在Xcfa2123-7A、Xgwm232- 1D和Xgwm429-2B位点分别检测到效应值大于4.0的等位变异。     

Similarities and differences between Amaranthus species and cultivars and estimation of outcrossing rate on the basis of electrophoretic separations of urea-soluble seed proteins

Wheat-rye translocation line (2BS/2RL) has been developed for resistance to biotype L of Hessian fly and agronomically useful traits. AFLP analysis using 64 primer pairs was conducted in order to identify 2RL-specific polymorphisms between “Coker 797” (non-2RL), near-isogenic line (NIL) carrying 2RL, and “Hamlet”. Nine primer combinations identified twelve reproducible polymorphic fragments in the NIL carrying 2RL. These twelve fragments were cloned and sequenced with an aim towards converting AFLP markers into sequence tagged sites (STS). A comparison of the 12 sequences with non-redundant accessions in the NCBI database using the BLAST search option indicated that one fragment of approximately 200 bp in length (amplified using primer combination E+AAC / M+CTA) was highly homologous with the rye-specific repetitive sequence R173-1 and Wis-2-lA, a retrotransposon-like element in wheat. Two STS primers (SJ07 and SJ09) out of twelve STS primer sets enabled the detection of polymorphisms between Coker 797 and NIL carrying 2RL. In order to verify whether the polymorphism detected by primers SJ07 and SJ09 was in fact the result of the presence of 2RL, additional plant material was examined. Amplified products of about 260 bp fragment with the SJ07 primer set were generated in rye cvs.“Chilbohomil” and “Jochunhomil”, triticale experimental line Suwon 15, and wheat experimental line K-14 (1AL/1RS & 2BS/2RL), as well as NIL carrying 2RL and Hamlet, but not in Coker 797 (non-2RL), “Keumgangmil” (non-translocation wheat), KS92WGRC17 (PI592729 /;/ 6BS/6BL-6RL), KS92WGRC19 (P1592731 /;/ 4BS/4BL-6RL), “TAM200” (1AL/1RS), and “Siouxland” (1BL/1RS). Our data suggest that primer set SJ07 amplifies a “2RL-specific” fragment of diagnostic value. This revised version was published online in August 2006 with corrections to the Cover Date.     

DNA profiling of pineapple cultivars in Japan discriminated by SSR markers

We developed 18 polymorphic simple sequence repeat (SSR) markers in pineapple (Ananas comosus) by using genomic libraries enriched for GA and CA motifs. The markers were used to genotype 31 pineapple accessions, including seven cultivars and 11 breeding lines from Okinawa Prefecture, 12 foreign accessions and one from a related species. These SSR loci were highly polymorphic: the 31 accessions contained three to seven alleles per locus, with an average of 4.1. The values of expected heterozygosity ranged from 0.09 to 0.76, with an average of 0.52. All 31 accessions could be successfully differentiated by the 18 SSR markers, with the exception of ‘N67-10’ and ‘Hawaiian Smooth Cayenne’. A single combination of three markers TsuAC004, TsuAC010 and TsuAC041, was enough to distinguish all accessions with one exception. A phenogram based on the SSR genotypes did not show any distinct groups, but it suggested that pineapples bred in Japan are genetically diversed. We reconfirmed the parentage of 14 pineapple accessions by comparing the SSR alleles at 17 SSR loci in each accession and its reported parents. The obtained information will contribute substantially to protecting plant breeders’ rights.     

新麦草Psathyrostachys juncea遗传变异的细胞学和分子的分析

本文用染色体C分带、同功酶和RAPD技术分析了来自不同地理分布的新麦草不同材料的单株,观察其c带的多态性,即同源染色体的配对,相同材料的不同个体之间,同一地区不同材料之间,以及不同来源的材料之间的多态性。10个同功酶揭示了14个假定标记位点,其中11个显示了多态性(平均66.2％,每个位点具2.6个等位基因)。大量的等位变化发生在多数的多态位点上。在所用试材中有近90％的等位变化。在优化条件下,200个测试引物中有55.5％的材料间产生了多态性的RAPDs带型。在同一材料中和不同材料间分别有55.7％和47.8％的扩增片断是多态的。C—带、同功酶和RAPD分析结果是互相确证而高度一致的,为新麦草的遗传变异提供了模式。 新麦草具有抗旱、耐盐碱和抗黄矮病的特性,可以在小麦育种工作上加以利用。     

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.     

Variations for Fusarium head blight resistance associated with genomic diversity in different sources of the resistant wheat cultivar ‘Sumai 3’

Fusarium head blight (FHB), caused by Fusarium graminearum, is a serious disease of wheat (Triticum aestivum L.) associated with contamination by the mycotoxin deoxynivalenol (DON). The FHB-resistant wheat cultivar ‘Sumai 3’ has been used extensively around the world. The existence of variation in FHB resistance among ‘Sumai 3’ accessions has been discussed. In this study, genetic variation among ‘Sumai 3’ accessions collected from six countries were identified using SSR markers; our results demonstrate unique chromosome regions in Sumai 3-AUT and Sumai 3-JPN (‘Sumai 3’ accessions from Austria and Japan, respectively). Field evaluation indicated strong resistance to FHB in Sumai 3-AUT. The polymorphic rate (number of polymorphic markers/number of available markers × 100) based on a DArT array was 12.5% between the two ‘Sumai 3’ accessions. Genotyping for DNA markers flanking FHB-resistant quantitative trait loci (QTLs) revealed genetic variations for the QTL regions on 5AS and 2DS; however, no variation was observed for the QTL regions on 3BS and 6B. Thus, the variation in FHB resistance among ‘Sumai 3’ accessions in the field is due to genetic diversity.     

Genetic variation in barley of crossability with wheat and its quantitative trait loci analysis

To study genetic variation in crossability, 80 barley accessions of diverse geographic origin consisting of 50 wild barleys (H. vulgare ssp. spontaneum or ssp. agriocrithon) and 30 cultivated barleys (H. vulgare ssp. vulgare) were crossed as the male parent with a highly crossable wheat variety, Shinchunaga. Crossabilities, expressed as the percentage of pollinated florets giving embryo-containing caryopses, ranged from 0% to 68.6%. Barley accessions from East Asia had generally a low crossability, while barley accessions from other regions exhibited a wider range of crossability including highly crossable genotypes. No significant difference in mean crossability was found between wild and cultivated barleys. To estimate the number and location of barley genes controlling the crossability, doubled haploid lines derived from the cross between the barley varieties Steptoe and Morex were crossed as the male parent with wheat. Quantitative trait loci (QTL) analysis using molecular markers identified four QTL. These were mapped to the centromeric regions of chromosomes 2H, 3H and 5H and the short arm of chromosome 7H. The QTL on chromosomes 3H and 5H had larger effects than those on chromosomes 2H and 7H. The four QTL collectively explained 35.4% of the total variance under a multiple QTL model. Relationships of the QTL identified in the present study with previously reported crossability genes of barley and wheat are discussed. This revised version was published online in August 2006 with corrections to the Cover Date.