Genetics of resistance to race TTKSK of Puccinia graminis f. sp. tritici in Triticum monococcum

Race TTKSK (or Ug99) of Puccinia graminis f. sp. tritici possesses virulence to several stem rust resistance genes commonly present in wheat cultivars grown worldwide. New variants detected in the race TTKSK lineage further broadened the virulence spectrum. The identification of sources of genetic resistance to race TTKSK and its relatives is necessary to enable the development and deployment of resistant varieties. Accessions of Triticum monococcum, an A-genome diploid wild and cultivated wheat, have previously been characterized as resistant to stem rust. Three resistance genes were identified and introgressed into hexaploid wheat: Sr21, Sr22, and Sr35. The objective of this study was to determine the genetic control and allelic relationships of resistance to race TTKSK in T. monococcum accessions identified through evaluations at the seedling stage. Generation F(2) progeny of 8 crosses between resistant and susceptible accessions and 13 crosses between resistant accessions of T. monococcum were evaluated with race TTKSK and often with North American races, including races QFCSC, TTTTF, and MCCFC. For a selected population segregating for three genes conferring resistance to race TTKSK, F(2:3) progeny were evaluated with races TTKSK, QFCSC, and TTTTF. In that population, we detected two genes conferring resistance to race TTKSK that are different from Sr21, Sr22, and Sr35. One of the new genes was effective to all races tested. The identification of these genes will facilitate the development of varieties with new resistance to race TTKSK.     

Inheritance and molecular mapping of barley genes conferring resistance to wheat stripe rust

ABSTRACT Most barley cultivars are resistant to stripe rust of wheat that is caused by Puccinia striiformis f. sp. tritici. The barley cv. Steptoe is susceptible to all identified races of P. striiformis f. sp. hordei (PSH), the barley stripe rust pathogen, but is resistant to most P. striiformis f. sp. tritici races. To determine inheritance of the Steptoe resistance to P. striiformis f. sp. tritici, a cross was made between Steptoe and Russell, a barley cultivar susceptible to some P. striiformis f. sp. tritici races and all tested P. striiformis f. sp. hordei races. Seedlings of parents and F(1), BC(1), F(2), and F(3) progeny from the barley cross were tested with P. striiformis f. sp. tritici races PST-41 and PST-45 under controlled greenhouse conditions. Genetic analyses of infection type data showed that Steptoe had one dominant gene and one recessive gene (provisionally designated as RpstS1 and rpstS2, respectively) for resistance to races PST-41 and PST-45. Genomic DNA was extracted from the parents and 150 F(2) plants that were tested for rust reaction and grown for seed of F(3) lines. The infection type data and polymorphic markers identified using the resistance gene analog polymorphism (RGAP) technique were analyzed with the Mapmaker computer program to map the resistance genes. The dominant resistance gene in Steptoe for resistance to P. striiformis f. sp. tritici races was mapped on barley chromosome 4H using a linked microsatellite marker, HVM68. A linkage group for the dominant gene was constructed with 12 RGAP markers and the microsatellite marker. The results show that resistance in barley to the wheat stripe rust pathogen is qualitatively inherited. These genes might provide useful resistance against wheat stripe rust when introgressed into wheat from barley.     

Sources and genetics of crown rust resistance in barley

ABSTRACT Crown rust, caused by Puccinia coronata var. hordei, is a new disease threat to barley in the Great Plains region of the United States. Deployment of resistant cultivars is the only economically viable option for the control of this disease. Thus, the objective of this study was to investigate the sources and genetics of crown rust resistance in barley. A geographically diverse sample of barley germ plasm collected around the world (526 accessions total) was evaluated at the seedling stage to P. coronata var. hordei, and only 10 accessions (1.9% of the total) were found resistant. These 10 accessions were also resistant at the adult plant stage in a greenhouse test. Three F(2) populations (Bowman x Hor2596, MR x Hor2596, and MD x Hor2596) were developed to study the inheritance of crown rust resistance in the resistant line Hor2596 (CIho 1243). A close fit to a 3:1 ratio of resistant/susceptible plants was observed in all three populations and is consistent with the segregation of a single resistance gene. F(1) plants from the Bowman x Hor2596 population exhibited slightly higher infection types than the resistant parent, indicating incomplete dominance. The locus symbol Rpc1 and allele symbol Rpc1.a were recommended for the crown rust resistance gene in Hor2596. An attempt was made to associate the Rpc1 locus with one of the seven barley chromosomes by analyzing linkage data with previously mapped morphological markers in crosses with multiple recessive (MR) and multiple dominant (MD) morphological marker stocks. However, no close linkages were detected between Rpc1 and the 20 morphological markers present in the marker stocks. The resistant accessions identified in this study should be useful to breeders for developing barley germ plasm with crown rust resistance.     

4个春小麦抗原对小麦秆锈菌 3个生理小种的抗病基因分析

 分析了春小麦4个重要抗原品种对小麦秆锈菌(Puccinia graminis var.tritici)3个生理小种的抗病基因,并对抗原品种所含有的抗病基因与国际上已命名的Sr基因进行了比较。结果表明:Minn2761携带对小种21C3显性的抗病基因Sr5Sr5和一对抗小种34C4的隐性的抗病基因;Alondra"S"携带Sr5Sr5和兼抗小种21C3、34C2、34C4的一对显性的抗病基因;Orofen携带Sr5Sr5和兼抗小种21C3、34C2的显性的抗病基因Sr6Sr6;Rulofen携带Sr6Sr6、一对抗小种21C3的隐性的抗病基因和另一对抗小种34C2的隐性的抗病基因。除了Sr5和Sr6基因之外,抗原品种所携带的另外四个抗病基因与国际上已命名的抗秆锈基因Sr1(即Sr9d)、Sr2、Sr5-Sr20、Sr22-Sr32、Sr36、Sr37是非等位的抗病基因。     

Genetic Diversity in Australian Populations of Puccinia graminis f. sp. avenae

ABSTRACT Sequence-tagged microsatellite profiling was used to develop 110 microsatellites for Puccinia graminis f. sp. tritici (causal agent of wheat stem rust). Low microsatellite polymorphism was exhibited among 10 pathogenically diverse P. graminis f. sp. tritici isolates collected from Australian cereal growing regions over a period of at least 70 years, with two polymorphic loci detected, each revealing two alleles. Limited cross-species amplification was observed for the wheat rust pathogens, P. triticina (leaf rust) and P. striiformis f. sp. tritici (stripe rust). However, very high transferability was revealed with P. graminis f. sp. avenae (causal agent of oat stem rust) isolates. A genetic diversity study of 47 P. graminis f. sp. avenae isolates collected from an Australia-wide survey in 1999, and a historical group of 16 isolates collected from Australian cereal growing regions from 1971 to 1996, revealed six polymorphic microsatellite loci with a total of 15 alleles. Genetic analysis revealed the presence of several clonal lineages and subpopulations in the pathogen population, and wide dispersal of identical races and genotypes throughout Australian cereal-growing regions. These findings demonstrated the dynamic population structure of this pathogen in Australia and concur with the patterns of diversity observed in pathogenicity studies.     

Effects of disease and plant competition on yield in monocultures and mixtures of two wheat cultivars

Disease seventy and crop yield were compared in monocultures and mixtures of two wheat cultivars. one susceptible and one resistant to Puccinia graminis f. sp. tritici. Part of each plot was inoculated and part treated with fungicide. Rust seventy was inversely related to the proportion of resistant plants present. Weight of grain in 100 heads of the susceptible cultivar increased as the amount of rust decreased. The susceptible cultivar yielded less than the resistant cultivar in monoculture, but was a stronger competitor in mixtures. Competitive abilities of the cultivars were independent of severity of rust in the mixtures studied.     

High and low pre-inoculation temperatures decrease the effectiveness of the Lr 20 and Sr 15 rust resistance genes in wheat

Spring wheat seedlings containing Lr 20 and Sr 15 resistance alleles were raised at 30° C, prior to inoculation with leaf rust ( Puccinia recondita race 76–2,3) and stem rust ( Puccinia graminis f.sp, tritici race 343–1,2,3,5,6) pathogens, respectively. Infected plants were then grown at one of seven temperatures in the range 18–30 C and infection types were scored at 10 days post-inoculation. These results were compared with those obtained for plants raised at a pre-inoculation temperature of 18° C. In both 18° C and 30° C pre-grown plants, a progressive increase in infection type was observed on resistant lines as post-inoculation temperature increased. However, resistant lines raised at 30°C had significantly higher infection types than plants raised at 18° C at all post-inoculation temperatures for which some degree of resistance was still evident in the plants raised at 18°C, The maximum temperature for expression of resistance was significantly higher for Lr 20 than for Sr 15. irrespective of pre-inoculation temperature. A lowering of the resistance expression was also evident in Sr 15 -bearing lines raised at a very low pre-inoculation temperature (4°C). The effects of low pre-inoculation temperature on resistance were assessed in both winter and spring wheat lines. These results are discussed in the light of current ideas concerning the host membrane location of pathogen recognition events.     

Mutants in wheat showing multipathogen resistance to biotrophic fungal pathogens

Five fast-neutron-derived mutants were isolated from the wheat line Hobbit 'sib' that show enhanced field resistance towards Puccinia striiformis f.sp. tritici , the causal agent of yellow rust. Subsequent testing showed the yellow rust resistance phenotypes to differ between mutants, to be expressed at different growth stages and, in some cases, to show an isolate interaction. Three mutants, I3-48, I3-49 and I3-54, exhibited an enhanced yellow rust resistance phenotype from the third seedling leaf onwards, while mutants I3-27 and I3-30 did not show an altered yellow rust phenotype until later growth stages. Additional resistance for brown rust (causal agent Puccinia triticina ) was identified in mutants I3-27, I3-30, I3-48 and I3-49, and for powdery mildew caused by Blumeria graminis f.sp. tritici in mutants I3-27, I3-30, I3-48 and I3-54, although in some cases the resistance was isolate-specific.     

81份春小麦种质资源抗条锈病评价

本研究结合苗期分小种接种和大田成株期自然诱发条件下对供试的81份春小麦资源进行抗条锈病鉴定,分析其抗条锈病情况、抗病类型及抗病性关系,结果表明:具全生育期抗条锈病类型的资源有7份,具成株期抗条锈病类型的资源有39份,有30份资源为含有成株期和对部分小种失去抗性的全生育期抗病性的抗性类型;苗期分别接种7个小种后,表现抗病的资源数为9~25份不等,表现中抗的资源为2~6份不等,表现感病的有50~69份不等,成株期表现抗病的73份,表现中抗的3份,感病的5份,即供试种质资源大部分表现为苗期感病,而成株期具有抗病性。聚类分析结果表明,该81份种质资源抗性聚类相对分散,遗传多样性水平较高。研究结果为小麦育种提供优良的抗条锈性资源。     

欧洲小麦品种Mega抗条锈病基因的遗传分析及分子标记

 本研究表明欧洲小麦品种Mega对我国小麦条锈病重要流行小种CYR30、CYR31、CYR32、Su-4和Su-14在苗期都具有良好的抗病性。采用小麦条锈菌小种CYR30对Mega与感病小麦品种铭贤169杂交的F₁、F₂和BC₁代及双亲进行苗期抗病性遗传分析,结果表明,Mega对CYR30的抗性由1对显性基因独立控制。采用SSR标记技术对其携带的抗性基因进行分子标记,在237对SSR引物中,发现位于5BL上的2个SSR引物位点Barc232、Wmc640在双亲和抗、感池间能扩增出稳定的特异性片段,与抗病基因连锁的遗传距离分别是3.7cM和8.6cM,暂命名为YrMe。本研究结果为科学利用Mega抗条锈基因培育抗病品种提供了依据。     

Genetic analysis and molecular mapping of wheat genes conferring resistance to the wheat stripe rust and barley stripe rust pathogens

ABSTRACT Stripe rust is one of the most important diseases of wheat and barley worldwide. On wheat it is caused by Puccinia striiformis f. sp. tritici and on barley by P. striiformis f. sp. hordei Most wheat genotypes are resistant to P. striiformis f. sp. hordei and most barley genotypes are resistant to P. striiformis f. sp. tritici. To determine the genetics of resistance in wheat to P. striiformis f. sp. hordei, crosses were made between wheat genotypes Lemhi (resistant to P. striiformis f. sp. hordei) and PI 478214 (susceptible to P. striiformis f. sp. hordei). The greenhouse seedling test of 150 F(2) progeny from the Lemhi x PI 478214 cross, inoculated with race PSH-14 of P. striiformis f. sp. hordei, indicated that Lemhi has a dominant resistance gene. The single dominant gene was confirmed by testing seedlings of the F(1), BC(1) to the two parents, and 150 F(3) lines from the F(2) plants with the same race. The tests of the F(1), BC(1), and F(3) progeny with race PSH-48 of P. striiformis f. sp. hordei and PST-21 of P. striiformis f. sp. tritici also showed a dominant gene for resistance to these races. Cosegregation analyses of the F(3) data from the tests with the two races of P. striiformis f. sp. hordei and one race of P. striiformis f. sp. tritici suggested that the same gene conferred the resistance to both races of P. striiformis f. sp. hordei, and this gene was different but closely linked to Yr21, a previously reported gene in Lemhi conferring resistance to race PST-21 of P. striiformis f. sp. tritici. A linkage group consisting of 11 resistance gene analog polymorphism (RGAP) markers was established for the genes. The gene was confirmed to be on chromosome 1B by amplification of a set of nullitetrasomic Chinese Spring lines with an RGAP marker linked in repulsion with the resistance allele. The genetic information obtained from this study is useful in understanding interactions between inappropriate hosts and pathogens. The gene identified in Lemhi for resistance to P. striiformis f. sp. hordei should provide resistance to barley stripe rust when introgressed into barley cultivars.     

Genetics of resistance to wheat leaf rust, stem rust, and powdery mildew in Aegilops sharonensis

Aegilops sharonensis (Sharon goatgrass) is a wild relative of wheat and a rich source of genetic diversity for disease resistance. The objectives of this study were to determine the genetic basis of leaf rust, stem rust, and powdery mildew resistance in A. sharonensis and also the allelic relationships between genes controlling resistance to each disease. Progeny from crosses between resistant and susceptible accessions were evaluated for their disease reaction at the seedling and/or adult plant stage to determine the number and action of genes conferring resistance. Two different genes conferring resistance to leaf rust races THBJ and BBBB were identified in accessions 1644 and 603. For stem rust, the same single gene was found to confer resistance to race TTTT in accessions 1644 and 2229. Resistance to stem rust race TPMK was conferred by two genes in accessions 1644 and 603. A contingency test revealed no association between genes conferring resistance to leaf rust race THBJ and stem rust race TTTT or between genes conferring resistance to stem rust race TTTT and powdery mildew isolate UM06-01, indicating that the respective resistance genes are not linked. Three accessions (1644, 2229, and 1193) were found to carry a single gene for resistance to powdery mildew. Allelism tests revealed that the resistance gene in accession 1644 is different from the respective single genes present in either 2229 or 1193. The simple inheritance of leaf rust, stem rust, and powdery mildew resistance in A. sharonensis should simplify the transfer of resistance to wheat in wide crosses.     

Histology of the infection of tritordeum and its parents by cereal brown rusts

The reactions of tritordeum lines and their Hordeum chilense and Triticum spp. parents to infection by Puccinia recondita f.sp. tritici, P. recondita f.sp. agropyri and P. hordei were studied at the seedling stage. The histological observations indicated that tritordeum behaves as the wheat parent, whatever the H. chilense parental line reaction. Tritordeum is to be considered a host of wheat brown rust where genes for hypersensitive resistance may occur; these are apparently contributed by the wheat parent. Both H. chilense and wheat are highly resistant to barley brown rust, and the reaction of tritordeum is that of the wheat parent with respect to the levels of necrosis associated with the early aborted infection units. The tritordeum reaction is also that of the wheat parent to a rust collected on H. jubatum (putatively P. recondita f.sp. agropyri ), with the susceptibility or resistance of H. chilense being overruled by the wheat parent reaction.     

Susceptibility in oats to stem rust induced by co-infection with leaf rust

Induction of susceptibility in oats to a normally avirulent pathotype of Puccinia graminis f.sp. avenae was studied in the presence of different pathotypes of P. coronata f.sp. avenae . Induction occurred on seedlings only in the presence of a virulent culture of P. coronata avenae and was not dependent on time or order of inoculation of either pathogen. This phenomenon was restricted to seedlings of lines possessing the Pg-a source of oat stem rust resistance. The specificity of induced susceptibility can be used as a valuable bioassay for screening and identifying Pg-a . Induced susceptibility occurred only at the seedling stage, and apparently provides no obstacle to the use of Pg-a as a source of stem rust resistance in oats.     

The ubiquity of non-specific eliciting activity in intercellular washing fluids from rust-infected wheat leaves

Intercellular washing fluids (IWF) were harvested from a range of wheat cultivars infected with either the leaf rust fungus ( Puccinia recondite f.sp. tritici ) or the stem rust fungus ( Puccinia graminis f.sp. tritici ). These fluids were then tested for their ability to elicit symptoms of chlorosis and necrosis in 14 wheat cultivars. Eliciting activity was found in all samples tested, irrespective of both the host cultivar infected by the rust fungus and the genotype of the infecting pathogen isolate. Healthy test cultivars either responded to all IWF preparations or were responsive to none of them. Investigations into the nature of this non-specific eliciting activity revealed that active molecules are periodate sensitive, negatively charged at neutral pH, and associated with a high molecular weight fraction.     

Comparison of Virulence and Isozyme Phenotypes of Pgt-QCCJ and Great Plains Races of Puccinia graminis f. sp. tritici

ABSTRACT Stem rust race Pgt-QCCJ was first found in the Great Plains of the United States in 1989, collected primarily from barley. This race became a major part of the Puccinia graminis f. sp. tritici population, even though it is virulent to only a few hard red winter wheat cultivars in the central Great Plains and to barley in the northern Great Plains. It threatens barley production in the northern Great Plains of the United States and Canada due to virulence to Rpg-1. Six differences in virulence and two in isozyme banding patterns from the most similar stem rust races make it unlikely that QCCJ arose as a mutant. Thus, QCCJ likely arose through sexual or parasexual recombination. Sexual recombination in the Great Plains is unlikely, as it has not been detected in many years. Avirulence to 'McNair 70l' is only known from the Pacific Northwest of the United States and adjacent Canada. The rust population in this area is of sexual origin, and the pattern of virulence/avirulence and isozyme banding for QCCJ occurs there. Pgt-QCCJ likely originated in the Pacific Northwest during or before 1989 and was wind-transported into the Great Plains.     

Virulence analysis of Puccinia graminis f.sp. tritici populations in Ethiopia with special consideration of Ug99

Wheat stem rust samples were collected in 2006 and 2007 in the Arsi, Bale, Shewa and northwest regions of Ethiopia to determine virulence diversity and race distribution in Puccinia graminis f.sp. tritici populations. Stem rust incidence was high in Arsi, Bale and east Shewa. In northwest Ethiopia, and north and west Shewa, stem rust was prevalent at low levels. A total of 152 isolates was analysed and 22 races were identified. Races TTKSR (Ug99), TTHSR and RRTTR were predominant, with frequencies of 26·6, 17·7 and 11·1%, respectively. These races were also detected in all regions. The highly virulent race designated Ug99 was present throughout the country and dominated in all regions except northwest Ethiopia. A variant of Ug99 virulent against the stem rust resistance gene Sr24 was not detected in this study. Four stem rust resistance genes ( Sr13, Sr30, Sr36 and SrTm p) were found to confer resistance to most of the races prevalent in Ethiopia. With the exception of Sr30 , which is not effective against Ug99, these genes could be used in breeding for resistance to stem rust in Ethiopia.     

Identification of a new pathotype of Puccinia hordei with virulence for the resistance gene Rph7

Barley leaf rust resistance gene Rph7, derived from barley accession Cebada Capa, is the most effective R-gene for resistance to Puccinia hordei. Virulence for this gene was known in the USA, Israel and Morocco but not yet in Europe. We found an unexpected leaf rust infection in the field at Córdoba, Spain in 2004 on Rph7 carrying lines. This virulence for Rph7 was confirmed in growth chamber experiments, being the first report of Rph7 virulence in European populations of P. hordei. A collection of 680 barley accessions was screened for resistance against this new isolate. Twelve accessions showed segregation with individual plants showing resistance based on hypersensitivity (low infection type). These individual resistant plants were selected and grown in the greenhouse to obtain seeds.     

小麦叶内杀菌剂含量对条锈病组分的定量影响

来源于澳大利亚的２５份麦类作物抗笥材料及中国８个省市的２２个小麦品种对禾谷胞囊线虫太谷群体的抗病性测定表明,６个由硬粒小麦的品种“Ｌａｎｇｄｏｎ”与节节麦的抗性材料为亲本合成的异源六倍体小麦均表现高抗;一些含有抗病基因Ｃｃｎ－１的品种,如Ｆｅｓｔｉｇｕａｙ和Ａｕｓ１０８９４等表现感病;其它来源于澳大利亚的６份燕麦及５份大麦材料也均高抗。     

茉莉酸诱导小麦抗病虫性初步研究

初步研究了茉莉酸诱导对小麦苗抗病虫能力的影响,结果显示,小麦在喷施茉莉酸后能够提高植株对麦长管蚜和小麦白粉病菌、小麦叶锈病菌的抵抗能力,可显著降低小麦白粉病、叶锈病的发病级别和病斑数量,对麦长管蚜则在体重和产仔数量上有显著的抑制作用。