Global status of wheat leaf rust caused by <Emphasis Type="Italic">Puccinia triticina</Emphasis>

Leaf rust caused by Puccinia triticina is the most common and widely distributed of the three wheat rusts. Losses from leaf rust are usually less damaging than those from stem rust and stripe rust, but leaf rust causes greater annual losses due to its more frequent and widespread occurrence. Yield losses from leaf rust are mostly due to reductions in kernel weight. Many laboratories worldwide conduct leaf rust surveys and virulence analyses. Most currently important races (pathotypes) have either evolved through mutations in existing populations or migrated from other, often unknown, areas. Several leaf rust resistance genes are cataloged, and high levels of slow rusting adult plant resistance are available in high yielding CIMMYT wheats. This paper summarizes the importance of leaf rust in the main wheat production areas as reflected by yield losses, the complexity of virulence variation in pathogen populations, the role cultivars with race-specific resistance play in pathogen evolution, and the control measures currently practiced in various regions of the world.     

12个主产区历史小麦品种抗叶锈病基因分析

近年来,小麦叶锈病发生有加重趋势,培育抗病品种是减轻小麦叶锈病危害的环保有效途径。用12个小麦品种及35个含已知抗叶锈病基因的载体品系在苗期接种19个不同毒性的叶锈菌生理小种,通过基因推导和系谱分析发掘待测品种中的抗叶锈病基因,并通过分子标记检测进一步验证;在田间接种强毒性混合生理小种,进行成株期病情严重度与普遍率调查,筛选慢锈性品种。结果表明,在石新828、百农3217、济南2号、泰山1号、石特14、晋麦2148、烟农15、小偃6号、温麦6号共9个品种中检测到Lr1、Lr26、Lr34、Lr37和Lr46共5个抗叶锈病基因,其中部分品种中发现多个抗性基因。成株期筛选出百农3217、平阳27、济南2号、泰山1号、石特14、晋麦2148、碧蚂4号、烟农15、小偃6号、温麦6号共10个慢叶锈性品种,其中碧蚂4号和小偃6号等品种是我国小麦育种的骨干亲本,探究这些品种中的抗病基因对培育小麦抗叶锈病品种具有重要意义。     

Suppression of stripe rust and leaf rust resistances in interspecific crosses of wheat

Stripe rust and leaf rust caused by Puccinia striiformis (Ps) Westend. and P. triticina (Pt) Eriks., respectively, are important foliar diseases of wheat worldwide. Breeding resistant wheat cultivars is the preferred strategy to control these diseases. Genes for resistance when introgressed from alien species or wheats of lower ploidy are frequently diluted effectiveness in the hexaploid wheat background or are completely suppressed. The objective of this study was to examine the expression of wheat stripe rust and leaf rust resistances derived from wild emmer wheat and Aegilops tauschii when combined in synthetic hexaploid lines. Eight amphidiploid wheat lines, synthesized by crossing five tetraploid wheats (AABB), viz. Triticum carthlicum var. darginicum, T. carthlicum var. fuligioscum, T. dicoccoides var. fuligioscum, T. durum with five lines of Ae. tauschii (DD), were evaluated in the seedling stage for resistance to five pathotypes of stripe rust caused by Ps and four pathotypes of leaf rust caused by Pt. Resistance in one or both parents was frequently suppressed in synthetic hexaploid lines, indicating the presence of suppressor genes in both Ae. tauschii and T. carthlicum var. darginicum. Specific suppression of resistance genes in the parental genotypes and to pathotypes of Ps and Pt were also observed. The presence and specificity of the suppressors for rust resistance obtained in this study provides useful knowledge for developing cultivars resistant to both rusts utilizing such genetic stocks in wheat breeding programs.     

Adaptation of wheat rusts to the wheat cultivars in former Czechoslovakia

Summary In former Czechoslovakia virulence of rusts attacking wheat was studied since the sixties. Since the same time genes for resistance in the registered cultivars were identified. The role of Berberis and Thalictrum as alternate hosts for stem rust and leaf rust, respectively, was investigated as well. Determined changes of virulence in rust populations could only partially be ascribed to changes of resistance genes in the grown cultivars. Unnecessary genes for virulence had no negative effect on the fitness of the pathogen. All tested samples of aeciospores from barberries attacked rye, not wheat. None of Thalictrum species occurring in the Czech and Slovak Republics was found to host wheat leaf rust. However, the sexual stage of wheat stem rust and wheat leaf rust could be induced on Berberis vulgaris and Thalictrum speciosissimum, respectively. General epidemiological conclusions are drawn from the results and experience of the last 35 years.     

CIMMYT小麦材料的苗期和成株抗叶锈病鉴定

选择来自CIMMYT的103个小麦品种(系)及35个含有已知抗叶锈基因的对照品种,苗期接种17个中国小麦叶锈菌小种以鉴定这些品种中可能含有的抗叶锈病基因, 并于2008-2009和2009-2010连续2年对这些材料进行成株抗叶锈病鉴定。通过苗期鉴定结合系谱分析和分子检测,在46个品种中共鉴定出Lr26、Lr34、Lr42和Lr47等4个抗叶锈病基因,其中9个品种携带Lr26基因,28个品种含有成株抗叶锈病基因Lr34基因,Lr42可能存在于11个品种中,还有2个材料可能含有Lr47,其他57个品种(系)对供试的15个小种多数表现为高抗,没有鉴定出已知的抗叶锈病基因。通过两年的田间抗叶锈病鉴定共筛选出46个表现慢锈的品种。苗期和田间结果表明,CIMMYT材料中含有丰富的对我国叶锈菌小种有效的苗期和成株抗叶锈基因,这些材料均可应用于我国小麦的抗叶锈病育种。     

Shifting boundaries: challenges for rust monitoring

Major changes have occurred in the global wheat-rust disease landscape over the last century. At the turn of the twentieth century pioneering rust research was driven by the need to combat devastating stem rust epidemics. A fundamental understanding of rust genetics and dispersal pathways emerged from this early work. Stem rust epidemics were also the driver behind the breeding programs that resulted in the green revolution of the 1960/70s. Successful incorporation of durable stem rust resistance into high yielding semi-dwarf wheat cultivars would change the wheat-rust disease situation beyond recognition. Associated intensification of the wheat cropping systems would also produce dramatic changes. Despite localized outbreaks, by the early 1990s stem rust was a disease under control. During this period of low stem rust incidence, yellow rust began to emerge as a substantial threat. Breakdown of Yr9 resistance resulted in damaging epidemics in Asia; an exotic incursion introduced yellow rust into Australia with highly significant subsequent impacts. The Australian incursion was almost certainly transmitted via an air traveller and the exponential growth in international air travel has increased the probability of other cross-continental movements. By the start of the twenty-first century, new rust threats had emerged. Durable stem rust resistance was broken down by the Ug99 race lineage identified in East Africa; new aggressive strains of yellow rust adapted to warmer temperatures were identified and spread across continents at a rapid rate. As in the past, major rust developments are one driver of global initiatives to mitigate the threat. Climate change and the response of pathogens to changing conditions are possible emerging issues, although other changes may prove to be more significant. Throughout this century of change a consistent theme is the adaptability of wheat-rust pathogens to cause recurring damage. Maintaining the gains of the previous decades will require sustained, collaborative, multi-disciplinary efforts. To keep pace with the evolving threats posed by wheat rusts there is a clear need for continuous vigilance and surveillance of both pathogen and host. Current international monitoring and surveillance efforts are described along with associated challenges.     

Genetic basis of seedling-resistance to leaf rust in bread wheat 'Thatcher'

The bread wheat cultivar ‘Thatcher’ is documented to carry the gene Lr22b for adult‐plant resistance to leaf rust. Seedling‐resistance to leaf rust caused by Puccinia triticina in the bread wheat cultivar ‘Thatcher’, the background parent of the near‐isogenic lines for leaf rust resistance genes in wheat, is rare and no published information could be found on its genetic basis. The F₂ and F₃ analysis of the cross ‘Agra Local’ (susceptible) × ‘Thatcher’ showed that an apparently incompletely dominant gene conditioned seedling‐resistance in ‘Thatcher’ to the three ‘Thatcher’‐avirulent Indian leaf rust pathotypes – 0R8, 0R8‐1 and 0R9. Test of allelism revealed that this gene (temporarily designated LrKr1) was derived from ‘Kanred’, one of the parents of ‘Thatcher’. Absence of any susceptible F₂ segregants in a ‘Thatcher’ × ‘Marquis’ cross confirmed that an additional gene (temporarily designated LrMq1) derived from ‘Marquis’, another parent of ‘Thatcher’, was effective against pathotype 0R9 alone. These two genes as well as a second gene in ‘Kanred’ (temporarily designated LrKr2), which was effective against all the three pathotypes, but has not been inherited by ‘Thatcher’, seem to be novel, undocumented leaf rust resistance genes.     

Genetic protection of wheat from rusts and development of resistant varieties in Russia and Ukraine

Leaf rust represents the major threat to wheat production in Russia and Ukraine. It has been present for many years and epidemics of the pathogen occur in different regions on both winter and spring wheat. In some regions there is evidence of more frequent epidemics, probably due to higher precipitation as a result of climate change. There is evidence that the virulence of the leaf rust population in Ukraine and European Russia and on winter wheat and spring wheat is similar. The pathogen population structure in Western Siberia is also similar to the European part, although there are some significant differences based on the genes employed in different regions. Ukrainian wheat breeders mostly rely on major resistance genes from wide crosses and have succeeded in developing resistant varieties. The North Caucasus winter wheat breeding programs apply the strategy of deploying varieties with different types of resistance and genes. This approach resulted in decreased leaf rust incidence in the region. Genes Lr23 and Lr19 deployed in spring wheat in the Volga region were rapidly overcome by the pathogen. There are continuing efforts to incorporate resistance from wild species. The first spring wheat leaf rust resistant varieties released in Western Siberia possessed gene LrTR which protected the crop for 10–15 years, but was eventually broken in 2007. Slow rusting is being utilized in several breeding programs in Russia and Ukraine, but has not become a major strategy.     

Wheat leaf rust resistance gene Lr59 derived from Aegilops peregrina

An Aegilops peregrina (Hackel in J. Fraser) Maire & Weiller accession that showed resistance to mixed leaf rust ( Puccinia triticina Eriks.) inoculum was crossed with, and backcrossed to, hexaploid wheat ( Triticum aestivum L.). During backcrossing a chromosome segment containing a leaf rust resistance gene (here designated Lr59 ) was spontaneously translocated to wheat chromosome 1A. Meiotic, monosomic and microsatellite analyses suggested that the translocated segment replaced most of, or the complete, 1AL arm, and probably resulted from centromeric breaks and fusion. The translocation, of which hexaploid wheat line 0306 is the appropriate source material, provided seedling leaf rust resistance against a wide range of South African and Canadian pathotypes.     

78份四川小麦育成品种(系)条锈病抗性鉴定与抗条锈病基因分子检测

四川省是小麦条锈菌新小种产生的重要地区之一,了解2016年以来四川小麦育成品种(系)对当前流行的条锈菌生理小种和致病类型的抗性水平以及明确其抗条锈病基因的分布状况,可为四川育种防控小麦抗条锈病和品种布局提供理论依据。本研究选择2个小种CYR32和CYR34对78份四川小麦育成品种(系)进行苗期鉴定,利用当前小麦条锈菌优势小种CYR32、CYR33、CYR34,以及贵22-14、贵农致病类群等混合菌进行成株期人工接种鉴定,并利用19个抗条锈病QTL和基因QYr.nwafu-4BL、Yr5、Yr10、Yr15、Yr17、Yr18、Yr26、Yr28、Yr29、Yr30、Yr36、Yr39、Yr41、Yr48、Yr65、Yr67、Yr78、Yr80和Yr81的分子标记对供试材料进行抗条锈病基因检测。结果表明,在78份供试材料的苗期鉴定中,对CYR32表现出抗性的有60份,占76.92%;对CYR34表现出抗性的有40份,占51.28%;同时对CYR32和CYR34表现抗性的有36份,占46.15%。78份小麦品种(系)在成株期均表现抗条锈病,其中绵麦835、蜀麦1743、蜀麦1829和蜀麦1868表现为免疫。苗期和成株期抗病性鉴定结果表明,成株期抗性材料有42份,占53.85%;全生育期抗性材料有36份,占46.15%。分子检测结果表明,可能携带QYr.nwafu-4BL、Yr15、Yr17、Yr18、Yr26、Yr28、Yr29、Yr30、Yr39、Yr41、Yr65、Yr67、Yr78、Yr80和Yr81的材料分别有5、5、45、2、30、5、30、39、3、2、22、8、23、6和24份。同时携带2~6个抗条锈病基因的聚合材料分别有24、22、11、14和3份,占94.87%。所有供试品种(系)均未检测到Yr5、Yr10、Yr36和Yr48,仅西科麦18未检测到上述19个抗条锈病基因,可能携带其他已知或新的条锈病抗性基因。本研究鉴定了78份四川小麦育成品种(系)对条锈病抗性水平整体较好,明确了其携带的抗条锈病基因,为利用其培育持久抗性小麦品种提供了科学依据。     

小麦多基因聚合体YW243的改良与利用

YW243是兼抗白粉、黄矮、三锈5种病害的普通小麦新种质。将其与农艺性状优良的丰产品种进行回交转育，选育出丰产、抗病的小麦新品系CB031、CB032、CB034和CB035。对这些新品系与YW243及回交亲本的抗性、品质、丰产性进行鉴定、比较分析，并用分子标记解析它们抗病性的遗传基础及其决定品质的高分子量麦谷蛋白亚基组成。结果表明，CB031是抗白粉病高产小麦新品系，至少含抗白粉病基因Pm2+6和高分子量麦谷蛋白亚基1, 7+9, 2+12；CB032和 CB034均为白粉病、条锈病免疫的小麦新品系，CB032至少含抗白粉病基因Pm2+Pm4+Pm21、抗条锈病基因YrX 4个基因和高分子量麦谷蛋白亚基7+9, 2+12；CB034至少含Pm21基因和高分子量麦谷蛋白亚基7+9, 5+10；CB035为免疫白粉病的优质小麦新品系，至少含Pm2+6+Pm21基因和高分子量麦谷蛋白亚基7+8, 2+12。CB031、CB032、CB034和CB035的穗粒性状、千粒重和秆高等农艺性状均较YW243有所改善。YW243是一个优良性状易于遗传、不良性状易于改造的育种亲本，有良好的应用前景。     

The reaction of x Tritordeum and its Triticum spp. and Hordeum chilense parents to rust diseases

Summary Hexaploid and octoploid tritordeums and their parents Hordeum chilense and Triticum spp. were screened for resistance to isolates of wheat and barley yellow and brown rusts. All H. chilense lines were highly resistant to both wheat and barley brown rust, few lines were susceptible to wheat yellow rust while susceptibility to barley yellow rust was common. In general the resistance of tritordeum is predominantly contributed by the wheat parent and apparently the genes for resistance in H. chilense are inhibited in their expression by the presence of the wheat genome.Abbreviations WYR wheat yellow rust - WBR wheat brown rust - BYR barley yellow rust - BBR barley brown rust     

Characterization of three wheat cultivars possessing new 1BL.1RS wheat-rye translocations

The wheat-rye 1BL.1RS translocation chromosomes have been used widely around the world in commercial wheat ( Triticum aestivum L.) production because of the presence of several disease resistance genes and a yield enhancement factor on the rye ( Secale cereale L.) chromosome. However, the recent reports of the loss of complete effectiveness of the disease resistance genes on the most commonly used 1BL.1RS chromosome have highlighted the need to seek and deploy additional sources of disease resistance genes. Three new sibling wheat cultivars, 'CN12', 'CN17' and 'CN18', were developed carrying 1RS arms derived from the rye inbred line L155. Genomic in situ hybridization and C-banding analysis revealed that all the three cultivars contained the rye chromosome 1RS arm fused to the wheat 1BL wheat chromosome arm. The three cultivars displayed high yields and high resistance to local powdery mildew and stripe rust pathotypes. Fluorescence in situ hybridization analysis indicated the different structure of 1BL.1RS chromosome between 'CN18' and the other two cultivars. The present study provides a new 1RS resource for wheat improvement.     

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.     

Seedling and adult plant resistance to yellow rust in Iranian bread wheats

In order to evaluate wheat response to yellow rust, 25 advanced, promising and commercial bread wheat cultivars were tested as seedlings in greenhouse conditions in Karaj, Iran, and as adult plants in field conditions at four locations. Five pathotypes of yellow rust, 14E176A⁺, 134E142A+, 6E210A+, 4E128A- and 64E146A+ prevailing in field test locations, were used in the seedling tests. The results showed that some of the cultivars have seedling or overall resistance to the pathotypes and some have adult plant resistance. Cultivars M-70-4 and MV17 were resistant to all pathotypes as seedlings and showed good adult plant resistance. This revised version was published online in August 2006 with corrections to the Cover Date.     

‘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.     

Identification and chromosomal locations of novel genes for resistance to powdery mildew and stripe rust in a wheat line 101-3

Wheat powdery mildew and stripe rust, caused by Blumeria graminis f.sp.tritici (syn. Erysiphe graminis f.sp.tritici) and Puccinia striiformis Westend., respectively, are two important fungal diseases of wheat in many regions in the world that cause significant annual yield losses. In the present study, a dominant powdery mildew and a dominant stripe rust resistance gene in wheat line 101-3 which derived from the progenies of the wide cross between common wheat and Dasypyrum villosum Candary L., was located on chromosome 6B and 1B, respectively, by monosomic analyses. The two genes are different from known resistance genes on chromosome 6B for powdery mildew and 1B for stripe rusts, suggesting that the two genes might be novel resistance genes for powdery mildew and stripe rust, respectively. It is uncertain whether the two genes are allelic or lined with other resistance genes located on chromosome 6B for powdery mildew and 1B for stripe rust. Further allelism tests are necessary to determine the relationships between the resistance gene and other genes located on chromosome 6B for powdery mildew and 1B for stripe rust through molecular markers.     

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。     

山西省小麦主栽品种抗叶锈病研究

选用14个具有不同毒性基因组合的叶锈菌系，推导分析了来自山西省6个育种单位和种子部门的24个重要小麦品种所携带的抗叶锈病基因状况。在供试的44个已知抗叶锈病基因(或基因组合)中，推导出了Lr1，Lr3，Lr13，Lr23，Lr26，Lr30等6个抗叶锈病基因，以单基因或基因组合形式分别分布在19个小麦品种中，其中Lr1，Lr3，Lr26是供试材料的主要已知抗叶锈病基因。成株期抗病性鉴定结果表明，在24个供试品种中，仅有晋麦62号和鲁麦14号两个品种表现出对叶锈病良好的抗性，晋麦31号、晋麦56号和晋麦61号3个品种表现为中抗至中感(杂合类型)，晋春9号、晋春13号、晋偃746—9等12个品种具有慢叶锈病特征。     

Durable resistance to the wheat rusts: integrating systems biology and traditional phenotype-based research methods to guide the deployment of resistance genes

Genes which confer partial resistance to the rusts in wheat figure prominently in discussions of potential durable resistance strategies. The positional cloning of the first of these genes, Lr34/Yr18 and Yr36, has revealed different protein structures, suggesting that the category of partial resistance genes, as defined by phenotype, likely groups together suites of functionally heterogenous genes. With the number of mapped partial rust resistance genes increasing rapidly as a result of ongoing advances in marker and sequencing technologies, breeding programs needing to select and prioritize genes for deployment confront a fundamental question: which genes or gene combinations are more likely to provide durable protection against these evolving pathogens? We argue that a refined classification of partial rust resistance genes is required to start answering this question, one based not merely on disease phenotype but also on gene cloning, molecular functional characterization, and interactions with other host and pathogen proteins. Combined with accurate and detailed disease phenotyping and standard genetic studies, an integrated wheat-rust interactome promises to provide the basis for a functional classification of partial resistance genes and thus a conceptual framework for their rational deployment.