Powdery mildew resistance in Aegilops tauschii coss. and synthetic hexaploid wheats

Summary A collection of 400 Ae. tauschii (syn. Ae. squarrosa) Coss. accessions were screened for powdery mildew resistance based on the response patterns of 13 wheat cultivars/lines possessing major resistance genes to nine differential mildew isolates. 106 accessions showed complete resistance to all isolates, and 174 accessions revealed isolate-specific resistance, among which were 40 accessions exhibiting an identical response pattern as wheat cultivar Ulka/^*8Cc which is known to possess resistance gene Pm2. Expression of both complete and isolate-specific resistance from Ae. tauschii was observed in some synthetic hexaploid wheats derived from four mildew susceptible T. durum Desf. parents, each crossed with five to 38 resistant diploid Ae. tauschii accessions. Synthetic amphiploids involving different combinations of T. durum and Ae. tauschii generally showed a decrease in resistance compared with that expressed by the Ae. tauschii parental lines.     

我国小麦农家品种和近缘种对白粉病的苗期抗性

由布氏白粉菌小麦专化型引起的白粉病是最重要的小麦叶部病害之一。抗性资源和抗性基因的发掘对控制该病害起了重要作用。小种专化抗性基因的抗性水平较高, 成为当前小麦生产上使用最为广泛的白粉病抗性基因。然而,这类抗性基因的广泛使用会导致菌系结构的改变, 并产生新的毒性小种。因此, 从大量小麦种质资源中鉴定新的、有效的白粉病抗性基因是一个长期的目标。为鉴定有效的白粉病抗源, 通过苗期接种国内流行白粉菌生理小种E09, 来评价258 份国内小麦农家品种和42 份小麦近缘种的抗性。结果表明, 有5份农家品种和20 份小麦近缘种对E09 表现免疫、近免疫或高抗。这25 份抗源被用来进一步接种另外5 个不同的国内生理小种E03、E05、E18、E20 和E23, 以推知它们所携带的未知抗性基因。通过与28 个已知白粉病抗性基因的抗谱进行比较发现, 这25 份小麦种质的抗性基因不同于Pm1a、Pm2、Pm3a、Pm3b、Pm3c、Pm3d、Pm3e、Pm3f、Pm4a、Pm4b、Pm4c、Pm5a、Pm6、Pm7、Pm8、Pm9、Pm17、Pm19、Pm24、Pm28 和Pm33等21 个已知抗性基因, 但与Pm1c、Pm1e、Pm12、Pm13、Pm16、Pm20 和Pm21 等7 个已知抗性基因仍需要进一步的区分。鉴于这25 份抗源与上述7 个已知抗性基因载体的来源不尽相同, 因此, 这些抗源很可能携带有未知的抗白粉病新基因, 但还需用更多的白粉菌生理小种来鉴定。本研究旨在从小麦农家品种及其近缘种中发掘新的有效抗源, 从而为抗白粉病新基因的发掘和有效利用奠定基础。     

Powdery mildew resistance of Nordic spring wheat cultivars grown in Estonia

Abstract

A group of spring wheat cultivars originating from Sweden, Finland, Norway, Germany, and the Netherlands was analysed for powdery mildew resistance. Using functional molecular markers, two alleles of the major resistance gene Pm3 were detected among the cultivars under the study. One of the alleles, Pm3d, was detected in the resistant cultivars ‘Vinjett’, ‘SW Estrad’, and ‘Zebra’, and in ‘Tjalve’, a cultivar of earlier release susceptible to the local population of powdery mildew. The second allele of Pm3 detected in the analysed group of cultivars was the allele Pm3f, rarely used in Europe. It was identified in the resistant cultivars ‘Satu’, ‘Helle’, and in the moderatively resistant cultivar ‘Mahti’. Pm3f was found to be effective against the local population of powdery mildew in Estonia, while Pm3d provided no protective effect. Besides the Pm3d allele on chromosome 1A, monosomic analysis of the cultivar ‘Vinjett’,which is almost immune to powdery mildew, identified two additional loci on chromosomes 5D and 7D, respectively, presumably responsible for the high resistance in this cultivar. In contrast to the earlier cultivars, six recently released cultivars (‘Vinjett’, ‘SW Estrad’, ‘Zebra’, ‘Satu’, ‘Helle’, ‘Meri’) demonstrated a high resistance to the powdery mildew fungus Blumeria graminis DC. f. sp. tritici both in the field and seedling tests, showing that the genetic basis of powdery mildew resistance in Nordic spring wheat has been improved noticeably in the last ten years.     

Identification of new sources for resistance to powdery mildew in H. spontaneum-derived winter barley lines

Twenty four barley lines derived from the F ₇generation of crosses between two winter barley cultivars and different accessions of Hordeum spontaneum Koch collected in Israel were tested against a set of ten European and five Israeli powdery mildew cultures, possessing virulence genes which completely match the spectrum of known mildew resistance genes. The comparison of reaction patterns justified the conclusion that new genes for resistance have been conferred from H. spontaneum which also differ from genes previously identified in other wild barley accessions from Israel. Participation in the expression of the resistance reaction of one of the two barley cultivars used in the development of the lines is well documented in some cases. The majority of the lines was found to be highly resistant against all or almost all European isolates, while various kinds of reactions were observed against the Israeli cultures. The effective transfer of novel mildew resistance from H. spontaneum into winter barley confirms similar results with spring barley, indicating natural wild barley populations in Israel as a significant gene pool for yet unexploited mildew resistance in barley.     

Resistance to powdery mildew in populations of barley landraces from Morocco

Forty-eight populations of barley landraces collected from Morocco were screened for resistance to powdery mildew and a number of different resistance genes were detected. Landraces originated from the collection of the International Center for Agricultural Research in the Dry Areas – ICARDA, Aleppo, Syria. Twenty populations of tested landraces (about 42%) showed resistance reactions and 46 single plant lines were selected. Fourteen of these lines were tested in the seedling stage with 17 and another 32 lines with 23 differential isolates of powdery mildew, respectively. The isolates were chosen according to their virulence spectra observed on the Pallas isolines differential set. Five lines originating from five populations of landraces showed resistance to all prevalent in Europe powdery mildew virulence genes. Thirty-five lines (76%) showed resistance reaction type 2. The distribution of reaction type scores indicated that about 81% of all reaction types observed were classified as powdery mildew resistance (scores 0, 1 and 2). In forty-one lines (89%) the presence of unknown genes alone or in combination with a specific one was detected. Four different resistance alleles (Mlat, Mla6, Mla14 and Mla22) were postulated to be present in the tested lines alone or in combination. Among specific resistance alleles the most common was allele Mlat (resistance Atlas). This allele was postulated to be present in twenty-three (50%) tested lines. The use of new identified sources of resistance to powdery mildew in barley breeding is discussed.     

Reaction to powdery mildew and stripe rust in related species and landraces of wheat

Field and controlled environmental tests indicated that the 49 accessions of closely related species and 12 landraces of wheat (Triticum aestivum L. em. Thell.) from the National Gene Bank of China showed different reactions to powdery mildew (Blumeria graminis (DC.) E. O. Speer. f. sp. tritici) and stripe rust (Puccinia striiformis Westend f. sp. tritici) at adult and seedling stages. Unknown Pm genes or alleles were postulated with Triticum baeoticum Boiss. accessions BO 3 and Triticum monococcum L. MO 4 and MO 5 when inoculated with 21 powdery mildew isolates at seedling stage. Fourteen accessions of T. baeoticum, T. monococcum, Triticum durum, and wheat landraces were inoculated with 30 stripe rust isolates at seedling stage. Unknown Yr genes or alleles were postulated with T. baeoticum Boiss. accession BO 5, as well as wheat landraces Xiaobaimai, Laomangmai, and Shaanxibai. Heterogeniety in reaction to powdery mildew isolates and stripe rust races were observed in related species and landraces of wheat.     

Exploring the Serbian GenBank barley (Hordeum vulgare L. subsp. vulgare) collection for powdery mildew resistance

Unlocking resistance genes in genbank collections are of prime importance for securing sustainable crop production. In this regard, the Serbian GenBank barley collection, comprising 93 local landraces and 36 commercial cultivars and elite barley breeding lines, was screened for novel resistances to powdery mildew (Blumeria graminis f. sp. hordei) using a set of 28 isolates with a wide spectrum of virulences/avirulences. No line was resistant to all the isolates, but one and three accessions showed resistance to 27 and 26 isolates, respectively. Twenty landraces (21.51 %) and ten cultivars (27.78 %) exhibited resistance to 50 % of the isolates. Infection type 2 was most frequent among resistant accessions. Nine B. graminis isolates were sufficient for gene postulation in 73 barley lines. In total, thirty-five different resistance spectra were recorded and the following known resistance genes were postulated namely, Mlra,Mlh,Mla12, Mla7(Mlu), Mlg, MlLa, Mla6, Mla7, Mlt, Mla22, Mlat, Mla1, Mlk. The majority of resistance profiles was constituted by only one line. Unidentified genes alone or in combination were proposed for twenty landraces and six cultivars. This report demonstrated that the barley collection held at the Serbian GenBank could be exploited as a new source for powdery mildew resistance.     

Genetic studies on the powdery mildew resistance of winter barley lines derived from Hordeum spontaneum accessions collected in Israel

The genetics of the powdery mildew resistance of 15 Hordeum spontaneum-derived winter barley lines were studied in testcrosses with selected cultivars carrying the MIa12 and MIa13 resistance alleles, in order to identify the inheritance of the resistance and to test for linkage with the MIa locus on chromosome 1H (5). A total of 27 genes were identified. Only one of these genes (in line 1–12 x Dura) could eventually be allelic to a gene previously identified in H. spontaneum Koch. A monofactorial dominant inheritance was identified in the majority of the lines. Three of the tested lines possessed recessively inherited genes and in one line a dominant and a recessive gene were identified. In respect to the reaction of the lines against European mildew cultures, lines with a bifactorially inherited resistance had a broader resistance spectrum than those with a monofactorial inheritance, while lines carrying recessive factors showed a moderately expressed resistance. In three cases a linkage with the MIa locus was found, while in two further lines a possible allelism to this locus was indicated by the absence of recombinant progeny plants. By using more than two isolates for linkage analysis, it was possible to identify additional genes for mildew resistance, reaching a maximum number of four genes in the same line. In some cases, a different inheritance was observed for the resistance of the same line against different isolates. It was assumed that different genes exist, each being effective against a different isolate.     

Transfer of leaf rust and stripe rust resistance from <Emphasis Type="Italic">Aegilops umbellulata</Emphasis> Zhuk. to bread wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

Aegilops umbellulata acc. 3732, an excellent source of resistance to major wheat diseases, was used for transferring leaf rust and stripe rust resistance to cultivated wheat. An amphiploid between Ae. umbellulata acc. 3732 and Triticum durum cv. WH890 was crossed with cv. Chinese Spring Ph ^I to induce homoeologous pairing between Ae. umbellulata and wheat chromosomes. The F₁ was crossed to the susceptible Triticum aestivum cv. ‘WL711’ and leaf rust and stripe rust resistant plants were selected among the backcross progenies. Homozygous lines were selected and screened against six Puccinia triticina and four Puccinia striiformis f. sp. tritici pathotypes at the seedling stage and a mixture of prevalent pathotypes of both rust pathogens at the adult plant stage. Genomic in situ hybridization in some of the selected introgression lines detected two lines with complete Ae. umbellulata chromosomes. Depending on the rust reactions and allelism tests, the introgression lines could be classified into two groups, comprising of lines with seedling leaf rust resistance gene Lr9 and with new seedling leaf rust and stripe rust resistance genes. Inheritance studies detected an additional adult plant leaf rust resistance gene in one of the introgression lines. A minimum of three putatively new genes—two for leaf rust resistance (LrU1 and LrU2) and one for stripe rust resistance (YrU1) have been introgressed into wheat from Ae. umbellulata. Two lines with no apparent linkage drag have been identified. These lines could serve as sources of resistance to leaf rust and stripe rust in breeding programs.     

小麦远缘杂交种质资源创新

小麦近缘种是改良小麦的一个重要基因库, 具有许多栽培小麦所不具备的优良特性。我们通过远缘杂交、染色体工程的方法创制了一大批不同类型的材料, 经基因组原位杂交GISH、多色FISH 和特异分子标记鉴定, 抗条锈病、白粉病、叶锈病鉴定, 品质、营养性状以及产量性状鉴定, 共选育出10 类可为育种家利用的抗病、优质、富含微量营养元素、氮高效、丰产性状优良的远缘杂交新种质和新不育系种质; 开发了414对黑麦基因组专化的EST 引物, 31 个黑麦染色体(臂)专化的EST 分子标记, 可应用于分子标记辅助育种, 或追踪检测小麦背景中的黑麦染色体或染色体片段; 进行了抗病新基因的遗传分析和分子标记定位工作。利用新种质, 选育出了一批表现突出的抗病、营养高效的小麦-黑麦、小麦-冰草远缘杂交新品系     

Powdery Mildew Resistance in a Collection of Chinese Barley Varieties

One hundred and forty-seven Chinese barley varieties maintained at the Gene Bank of the National Barley Improvement Centre, Zhejiang, and 84 progenies from these varieties were tested at the seedling stage for their reaction to 32 selected pathotypes of Blumeria graminis f. sp. hordei. Eighteen resistance spectra were identified comprising single or combined resistances from eight known (Ml(Bw), Ml(Ch), Mla7, Mla8, Mla9, Mla13, MlaRu4 and Mlg) and six unknown resistance genes. The most frequent gene was Ml(Bw), which was found in 69 varieties and previously detected in only a few European winter barley varieties. The genes Mla8 and Ml(Ch) were also often present, but other resistance genes were rare. After inoculation, considerably fewer pathogen colonies were observed in ‘Aiganqi’ and one line of ‘Tong5’. Twenty varieties were composed of lines with different resistance genes. China is likely to be a region of origin of the genes Ml(Bw), Mla7, as well as three unknown genes found in original landraces and perhaps another three unknown genes detected in cultivars bred in China. The resistances of varieties from the Zhejiang province and those originating from 11 other Chinese provinces were quite different. Unfortunately, none of the varieties are promising sources of resistance to powdery mildew and China does not seem to be a region suitable for identifying such sources.     

Analysis of Wheat Disease Resistance Data Originating from Screenings of Gatersleben Genebank Accessions during 1933 and 1992

Series of 10,348 accessions belonging to 21 species (hexaploid, tetraploid, diploid) of the genus Triticum and 489 accessions belonging to 20 species of the genus Aegilops were scored for disease resistance during a period of 60 years. Tests were performed at the seedling stage for powdery mildew (Erysiphe graminis DC. f. sp. tritici March.), leaf rust (Puccinia recondita Rob. ex Desm. f. sp. tritici Erikss.), stripe rust (Puccinia striiformis West. f. sp. tritici Erikss.) and eyespot (Pseudocercosporella herpotrichoides (Fron.) Deight.) but also at the adult plant stage considering powdery mildew, leaf rust, stripe rust, eyespot and glume blotch (Septoria nodorum Berk.). About 150,000 disease scores recorded on index cards using different scoring scales were transferred to the computer, converted into a 1–9 scale and used to summarise the results. Within the genus Triticum 20% of the material analysed was classified as heterogeneous. For the accessions without detectable segregation a large variability for resistance/susceptibility was detected. At the adult plant stage resistant accessions without visible infections were identified for all diseases. The percentages of resistant accessions at that growth stage were always higher than the ones found in the material tested at the seedling stage. The probability for finding resistant material was shown to be highest in the diploid species ( > 50%) but decreased with increasing ploidy level to about 10% in the hexaploids. For Aegilops it was shown that most of the accessions were homogeneous and highly resistant against powdery mildew (seedling and adult plant stage), leaf rust (adult plant stage) and eyespot (seedling and adult plant stage/natural infection). The data obtained for the individual accessions are available via Internet (http://www.ipk-gatersleben.de). An erratum to this article is available at .     

Sources of Resistance to Stem Rust (<Emphasis Type="Italic">Puccinia graminis</Emphasis> f. sp. <Emphasis Type="Italic">tritici</Emphasis>) in Ethiopian Tetraploid Wheat Accessions

Seedlings of 41 emmer (Triticum dicoccon Schrank) and 56 durum (T. durum Desf.) wheat accessions were evaluated for their response to stem rust (Puccinia graminis f. sp. tritici) infection under greenhouse condition at Kulumsa Agricultural Research Center, Ethiopia. The objectives were to identify tetraploid wheat accessions that could serve as sources of resistance to stem rust, and postulate the stem rust (Sr) resistance genes through multipatotype testing. The test included screening of accessions for stem rust resistance and multipatotype testing. To ensure vigorous screening, a mixture of six isolates (Si-1a, Am-2, Ku-3, Dz-4a, Ro-4 and Na-22) that were collected from severely infected emmer, durum, and bread wheat (Triticum aestivum L.) varieties of major wheat growing areas of Ethiopia was used as inocula. Out of the tested accessions, 18 emmer and 6 durum accessions exhibited low infection types (0–2) response and hence selected as a source of resistance to stem rust infection. Multipatotype testing was done to postulate Sr genes in the selected accessions. In the test, 10 different stem rust races (A2, A9, A11, A14, A16, A17, B3, B7, B15, and B21), 33 stem rust differential lines, and a universal susceptible check variety, Morocco were used, The high (3–4) and low infection type reaction patterns of the tested accessions and differential lines were used to postulate the genes that exhibit gene-for-gene relationship. The presence of Sr 7b, 8b, 9a, 9b, 10, 14, 24, 27, 28, 29, 30, 31, 32 and Tt-3+10 genes were postulated in 16 selected emmer and 5 durum wheat accessions. Efforts to transfer these valuable Sr genes from cultivated tetraploid wheats could be rewarding to get stem rust resistant varieties and boost wheat production.     

小麦抗叶锈病基因Lr2c的SSR标记

选取抗叶锈病基因位于2D染色体上的TcLr2c等7个小麦（Triticum aestivum）近等基因系、感病亲本Thatcher及215株TcLr2c与Thatcher杂交F2代为材料,研究抗叶锈病基因Lr2c SSR分子标记。从筛选的29对位于小麦2D染色体的SSR引物中获得4对能够揭示Lr2c多态性的分子标记,通过215株TcLr2c × Thatcher F2群体验证,结果表明Xgwm261和Xgwm296与Lr2c紧密连锁,其距目的基因的遗传距离分别为1.9和3.6 cM,可用于小麦抗叶锈病分子辅助育种。     

小麦品种与育种材料抗气传病害鉴定研究

用山西省目前小麦气传病害(包括条锈病、叶锈病和白粉病)主要优势生理小种和致病类型的混合菌,采用人工接菌方法,对1111份小麦品种和育种材料进行抗病性鉴定,并对其中479份小麦品种和育种材料进行条锈菌分小种鉴定,累计5357种次,为育种提供抗病信息、抗源材料,并为小麦品种审定提供抗、耐病依据。     

建国以来黑龙江省春小麦抗白粉病基因检测及其组成分析

为了解黑龙江省春小麦抗白粉病基因的组成及分布规律,本研究利用已开发的Pm2、Pm3b、Pm4、Pm8、Pm13和Pm21抗白粉病基因分子标记对黑龙江省推广的123份小麦品种进行了检测和分析。结果表明,在123份小麦品种中分布4种抗白粉病基因,其中Pm2、Pm3和Pm13分布频率较高,分别为95.1%、95.1%和94.3%,Pm8分布频率较低,仅为0.01%,且不存在抗白粉病基因Pm4和Pm21;黑龙江省春小麦抗白粉病基因组合共有7种类型,其中Pm2/Pm3b/Pm13类型所占比例最高,为88.6%,其次为Pm2/Pm3b、Pm2/Pm13和Pm3b/Pm13,所占比例分别为3.3%、2.4%和2.4%,Pm2和Pm2/Pm3b/Pm8/Pm13所占比例最低,为0.8%。本试验结果明确了建国后黑龙江省春小麦品种抗白粉病基因的组成和分布频率,为高效开展小麦抗白粉病育种提供了一定的理论依据。     

Resistance to wheat leaf rust in Aegilops tauschii Coss. and inheritance of resistance in hexaploid wheat

A collection of 164 Aegilops tauschii accessions, obtained from Gatersleben, Germany, was screened for reaction to leaf rust under controlled greenhouse conditions. We have also evaluated a selection of synthetic hexaploid wheats, produced by hybridizing Ae. tauschii with tetraploid durum wheats, as well as the first and second generation of hybrids between some of these resistant synthetic hexaploid wheats and susceptible Triticum aestivum cultivars. Eighteen (11%) accessions of Ae. tauschii were resistant to leaf rust among which 1 was immune, 13 were highly resistant and 4 were moderately resistant. Six of the synthetic hexaploid wheats expressed a high level of leaf rust resistance while four exhibited either a reduced or complete susceptibility compared to their corresponding diploid parent. This suppression of resistance at the hexaploid level suggests the presence of suppressor genes in the A and/or B genomes of the T. turgidum parent. Inheritance of leaf rust resistance from the intercrosses with susceptible bread wheats revealed that resistance was dominant over susceptibility. Leaf rust resistance from the three synthetics (syn 101, syn 701 and syn 901) was effectively transmitted as a single dominant gene and one synthetic (syn 301) possessed two different dominant genes for resistance.     

小麦新品系2-26中抗白粉病基因的遗传分析和RAPD标记

由小麦白粉病菌引起的白粉病是世界上很多小麦种植区的主要病害之一。本研究对稳定抗白粉病品系2-26中的抗病基因采用常规遗传方法进行了分析。结果表明,2-26中存在一对显性抗白粉病基因,暂命名为Pm2-26。运用RAPD方法对白粉病抗感亲本和抗感池进行DNA多态性分析,获得2个紧密连锁的RAPD标记（SBSC2和SBSI2...     

Phenotypic diversity of barley powdery mildew resistance sources

One hundred and twenty-one of 123 previously detected new sources of wild barley (Hordeum vulgare ssp. spontaneum) resistant to powdery mildew (Blumeria graminis f. sp. hordei), and originating from Mediterranean area, and 20 standards were tested at the seedling stage for reaction to 38 selected Israeli powdery mildew isolates. The obtained resistance spectrum (a set of resistant and susceptible reactions) of each accession was divided into triplets and converted to octal numbers. This concentrates information on the resistance phenotype of each accession and makes their comparison much easier. One hundred and thirty-four different resistance spectra were determined. No compatible reaction was found in standards possessing genes mlo and Mlhb2 and in the accession PI 466634. The results demonstrate large diversity in new resistance sources, their distinction from the sources described till now as well as diversity in powdery mildew resistance of wild barley in the Mediterranean area. The results facilitate more effective further studies of such a large set of new resistance sources, and contribute to speeding up their use in barley breeding.     

Evaluation of cultivated and wild barley for resistance to pathotypes ofPuccinia hordei with wide virulence

An isolate ofPuccinia hordei (ND89-3) originally collected in Morocco is virulent on most barley genotypes reported to possess resistance, except cultivar Estate (CI 3410), which possesses theRph3 gene and exhibits a low to intermediate level of resistance (infection type 12). Isolate ND89-3 possesses one of the widest virulence spectrums reported forP. hordei. Accessions ofHordeum vulgare (1,997 in total) andH. spontaneum (885 in total), mostly originating from the Mediterranean region and parts of North Africa, were evaluated with isolate ND89-3 at the seedling stage to identify new sources of leaf rust resistance. Fifty-eight accessions ofH. vulgare, and 222 accessions ofH. spontaneum exhibited low infection types to this isolate. Further evaluations of these resistant accessions with isolates ofP. hordei virulent forRph3,Rph7, andRph12 suggested that most of the resistantH. vulgare accessions possess theRph3 gene. Data suggested additional sources of effective resistance inH. vulgare are rather limited. FiveH. vulgare accessions and 167H. spontaneum accessions were identified as possible sources of new genes for leaf rust resistance. These accessions likely possess resistance genes that are different fromRph1 toRph12, or gene combinations thereof based on their reaction to four leaf rust isolates. Utilization of these accessions in barley breeding will broaden the germplasm resources available for genetic control ofP. hordei. North Dakota Agricultural Experiment Station Journal Series No. 2123. The U.S. Government right to retain a non-exclusive, royalty free licence in and to any copyright is acknowledged.