Yr5-virulent races of Puccinia striiformis f.sp.tritici possess relative parasitic fitness higher than current main predominant races and potential risk

Wheat stripe rust,caused by Puccinia striiformis f.sp.tritici(Pst),is one of the most destructive fungal diseases of wheat,and seriously threatens safe production of the crop worldwide.In China,new races historically appeared and rapidly developed to be predominant races and have resulted in ineffectiveness and replacement of wheat resistance cultivars as well as massive reduction in yield.In the present study,the relative parasitic fitness of the two newlyemerged Yr5-virulent races(TSA-6 and TSA-9)were compared with those of four currently predominant Chinese races(CYR31,CYR32,CYR33,and CYR34)based on evaluation on 10 Chinese wheat cultivars.As a result,there were significant differences in the relative parasitic fitness parameters among overall tested races based on multiple comparison(LSD)analysis(P<0.05).The principal component analysis(PCA)of overall parasitic fitness parameters indicated that the sporulation ability,infection and spore survivability,expansion capacity,and potential pathogenicity were the most important parasitic fitness attributes of the tested races.Based on the establishment of extracted three principal components and a comprehensive factor score mathematical models,evaluations of the parasitic fitness attributes of tested races showed that the level of relative parasitic fitness of the tested six races was:CYR32(1.15)>TSA-9(0.95)>TSA-6(0.92)>CYR34(0.29)>CYR31(–1.54)>CYR33(–1.77).The results indicated that two Yr5-virulent races TSA-9 and TSA-6 possessed relative parasitic fitness higher than races CYR34,CYR31,and CYR33,but lower than race CYR32,and have potential risks in developing to be predominant races.Therefore,continual monitoring of both Yr5-virulent races,and their variants is needed.The use of wheat cultivars(lines)with Yr5 resistance gene singly in wheat breeding is essential for being avoided,and is suggested to combine with other effective stripe rust resistance genes.

Characterization of wheat monogenic lines with known Sr genes and wheat cultivars for resistance to three new races of Puccinia graminis f. sp. tritici in China

Wheat stem rust, caused by Puccinia graminis f. sp. tritici(Pgt), is a potentially devastating fungal disease of wheat worldwide. The present study was to evaluate the resistance of 42 wheat monogenic lines with known stem rust resistance(Sr) genes and 69 wheat cultivars to three new Pgt races(34C0MRGQM, 34C3MKGQM, and 34C6MTGSM)identified from aeciospores at the seedling and adult-plant stages. The phenotyping results revealed that monogenic lines harboring resistance genes Sr9e, Sr17, Sr21, Sr22, Sr26, Sr30, Sr31, Sr33, Sr35, Sr36, Sr37, Sr38, Sr47, SrTmp,and SrTt3 were effectively resistant to all three Pgt races at the seedling and adult-plant stages. In contrast, monogenic lines containing Sr5, Sr6, Sr7b, Sr9a, Sr9d, Sr9f, Sr9g, Sr9b, Sr16, Sr24, Sr28, and Sr39 were highly susceptible to these races at both seedling and adult-plant stages. The other lines with Sr8a, Sr10, Sr11, Sr13, Sr14, Sr15, Sr18, Sr20,Sr19, Sr23, Sr25, Sr27, Sr29, Sr32, and Sr34, displayed variable levels of resistance to one or two of the tested races.Seedling infection types(ITs) and adult-plant infection responses(IRs) indicated that 41(59.4%) of the wheat cultivars showed high resistance to all the three races. Molecular marker analysis showed that four wheat culitvars likely carried Sr2, 20 wheat culitvars likely carried Sr31, 9 wheat culitvars likely carried Sr38, and none of the cultivars carried Sr24,Sr25, and Sr26. Our results provide a scientific basis for rational utilization of the tested Sr genes and wheat cultivars against these novel Pgt races.

Research Advances in New Race Ug99 of Puccinia graminis f.sp. tritici

This paper reviewed the research advances of Ug99 and its resistance breeding from the aspects of its discovery, race variation, pathogenicity, distribution, spread, exploration of relative resistant genes, linked molecular marker selection and resistance breeding strategies, to provide basis for comprehensive understanding of the new Puccinia graminis f. sp. tritici race Ug99 and its potential threat to wheat production. Ug99 is a new Puccinia grarninis f. sp. tritici race with high variability, strong pathogenicity and rapid spread speed, which is likely to cause global damages to world wheat production. We should strengthen the exploration and utilization of new resistance genes in wheat and relative species and breeding of new wheat varieties with durable resistance, to control and prevent damages caused by Ug99 and its variants.

Identification of eight Berberis species from the Yunnan-Guizhou plateau as aecial hosts for Puccinia striiformis f.sp.tritici,the wheat stripe rust pathogen

Puccinia striiformis Westend.f.sp.tritici Erikss.(Pst)infects wheat and causes stripe rust.The rust is heteroecious with wheat as the primary uredinial and telial host and barberry(Berberis spp.)as the alternate pycnial and aecial host.More than 40 Berberis species have been identified as alternate hosts for Pst,and most of these are Chinese Berberis species.However,little is known about Berberis species or their geographic distributions in the Yunnan-Guizhou plateau in southwestern China.The Yunnan-Guizhou plateau is considered to be an important and relatively independent region for the evolution of the wheat stripe rust pathogen in China because the entire disease cycle can be completed within the region.In this study,we conducted a survey of barberry plants in the Yunnan-Guizhou plateau and identified the eight Pst-susceptible Berberis species under controlled conditions,including B.julianae,B.tsienii,B.veitchii,B.wilsonae,B.wilsonae var.guhtzunica,B.franchetiana,B.lepidifolia and B.pruinosa.These species are reported here for the first time to serve as alternate hosts for the wheat stripe rust pathogen under controlled conditions.

Association Analysis of SP-SNPs and Avirulence Genes in Puccinia striiformis f. sp. tritici, the Wheat Stripe Rust Pathogen

Puccinia striiformis f. sp. tritici (Pst) is one of the pathogenic fungi on wheat, caused stripe rust that is a great threat for wheat production all over the world. Intensive efforts have been made to study genetics of wheat resistance to this disease, but few on avirulence of the pathogen due mainly to the nature of obligate biotrophism and the lack of systems for studying its genetics and molecular manipulations. To overcome these limitations, a natural Pst population comprising 352 isolates representative of a diverse virulence spectrum was genotyped using 97 secreted protein-single nucleotide polymorphism (SP-SNP) markers to identify candidate avirulence genes using association analysis. Among avirulence genes corresponding to 19 resistance genes, significantly associated SP-SNP markers were detected for avirulence genes AvYr1, AvYr2, AvYr6, AvYr7, AvYr8, AvYr44, AvYrExp2, AvYrSP, and AvYrTye. These results indicate that association analysis can be used to identify markers for avirulence genes. This study has laid the foundation for developing more SP-SNPs for mapping avirulence genes using segregating populations that can be generated through sexual reproduction on alternate hosts of the pathogen.

An improved method for RNA extraction from urediniospores of and wheat leaves infected by an obligate fungal pathogen, Puccinia striiformis f. sp. tritici

Stripe rust, caused by Puccinia striiformis f. sp. tritici, is an important wheat disease in China, seriously threatening wheat production. Understanding the winter survival of the fungus is a key for predicting the spring epidemics of the disease, which determines the crop loss. Estimation of P. striiformis f. sp. tritici winter survival requires processing a large number of samples for sensitive detection of the pathogen in wheat leaf tissue using real-time quantitative reverse transcription PCR （qRT-PCR）. A bottleneck for the analysis is the acquisition of a good yield of high quality RNA suitable for qRT-PCR to distinguish dead and alive fungal hyphae inside leaves. Although several methods have been described in the literatures and commercial kits are available for RNA extraction, these methods are mostly too complicated, expensive and inefficient. Thus, we modified three previously reported RNA extraction methods with common and low-cost reagents （LiCI, SDS and NaCI） to solve the problems and selected the best to obtain high quality and quantity RNA for use in qRT-PCR. In the three improved methods, the NaCI method was proven to be the best for extracting RNAfrom urediniospores of and wheat leaves infected by P. striiformis f. sp. tritici, although the modified LiCI and SDS methods also increased yield of RNA compared to the previous methods. The improved NaCI method has the following advantages： 1） Complete transfer of urediniospores of P. striiformis f. sp. tritici from the mortar and pestle can ensure the initial amount of RNA for the qRT-PCR analysis; 2） the use of low-cost NaCI to replace more expensive Trizol can reduce the cost; 3） the yield and quality of RNA can be increased; 4） the improved method is more suitable for a large number and high quantity of samples from fields. Using the improved NaCI method, the amount of RNA was increased three times from urediniospores of P. striiformis f. sp. tritici compared from the extraction kit. Approximately, 10.11 IJg total RNA of high quality was obtained from 100 mg of infected leaves, which was 8.8, 6.5, 3.4 and 2.1 folds of the amounts obtained from the previous LiCI, SDS, NaCI and traditional Trizol methods, respectively. The method could be used to study the overwintering rates of R striiformis f. sp. tritici over a large region of wheat production for predicting epidemic levels by determining pathogen survival levels after winter. The method can alsobe used in any studies which need a large number of high quality RNA samples.

The TaFIM1 gene mediates wheat resistance against Puccinia striiformis f. sp. tritici and responds to abiotic stress

Fimbrin, a regulator of actin cytoskeletal dynamics that participates in numerous physiological and biochemical processes, controls multiple developmental processes in a variety of tissues and cell types. However, the role of fimbrin in pathogen defense of wheat and the mechanisms have not been well studied. Here, we investigated that the expression of TaFIM1 gene of wheat was significantly induced in response to avirulent race of Puccinia striiformis f. sp. tritici(Pst) and silencing of TaFIM1 by virus-induced gene silencing method. The results show that silencing of TaFIM1 resulted in a reduction of resistance against the stripe rust indicated by both phenotypes and a histological examination of Pst growth. Additionally, the expression level of Ta FIM1 gene was up-regulated under abiotic stresses. These findings suggest that Ta FIM1 functions as a positive regulator of pathogen resistance of wheat plants and response to abiotic stress. Our work may show new light on understanding the roles of fimbrin in wheat.

Effects of Different Cultivation Patterns of Wheat on Population Structure of Puccinia striiformis West.f. sp. tritici

The paper was to study the effects of different cultivation patterns( mix cultivation and monocultivation) of wheat on population structure of Puccinia striiformis West. f. sp. tritici in the fields. Five race-specific-markers( CY32,CY31,CY29,CY23 and Shuiyuan pathotype) were used to survey 113 infected samples collected from two cultivation patterns. The results indicated that frequency of race-specific-markers under monocultivation was higher than that under mix cultivation; the dominant race-specific-markers were CY32 and CY29 under monocultivation,and the frequency of detection were 81. 5% and 78. 5%,respectively. The dominant race-specific-markers were CY29 and Shuiyuan pathotype under mix cultivation,and the frequency of detection are 41. 7% and 18. 8%,respectively.Several race-specific-markers were detected in single infected leaf,and 41. 7% of infected single leaf were detected with more than two race-specific-markers,58. 3% of infected single leaf were detected with one race-specific-marker under mix cultivation pattern,while there were 75. 0% infected leaves with more than two race-specific-markers and 25. 0% infected single leaf detected with one race-specific-marker under monocultivation pattern. The results indicated that mix cultivation pattern of wheat can reduce races on single leaf,affect the distribution of races in infected leaves,and suppress the occurrence frequency of dominant races of P. striiformis in the fields significantly,subsequently reduced severity and prevalence of the disease.

Study Genetic Variation Using DNA Molecular Markers and Identification Physiological Races of Wheat Stripe （yellow） Rust Puccinia striiformis f.sp tritici during 2010-2014 in Some Regions of Syria

Yellow Rust （stripe） rust （Puccinia striiformis West. f. sp. tritici） is one of the most epidemic diseases infect wheat in cold and wet regions. In 1988, this disease caused a loss of seasonal production amounted 70% on wheat variety Mexipak in Syria, and recurrent infection in 2010, caused by a virulent race called Yr27, caused a considerable loss in the production of bread wheat cultivars （Cham 8, Cham 6 particularly） amounted 90%. Recently, 15 races of yellow rust had been addressed in Syria for seasons 2010-2014; 159E256, 166E254, 166E256, 255 E112, 0 E0, 64 E 6, 230 El50, 0 E 18, 198 El30, 166 El50, 102 El60, 128 E0, 126 El50, 214E150, and 6E16. The race 6E16 was the most frequent during the two seasons, while the race 255El12 was the most virulent, followed by the race 230E222 and the race 0E0 was the weakest one. This study revealed the presence of fourteen newly observed races in Syria. Molecular Variance Analysis of Molecular Variance （AMOVA） of 55 yellow rust Puccinia striiformis f.sp tritici isolates examined by Amplify Fragment Length Polymorphism （AFLP） revealed high genetic variation within population, and the dimensional scale analysis （MSD） and tree diagram showed that the Syrian yellow rust isolates were clustered in three groups： the first group contained isolates derived from durum wheat, the second one contained bread wheat isolates, but the third was made of isolates derived from both durum and bread wheat species.

Population Diversity of Puccinia graminis is Sustained Through Sexual Cycle on Alternate Hosts

A high degree of virulence diversity has been maintained in the population of Puccinia graminis f. sp. tritici （Pgt） in northwestern United States. Although Berberis vulgaris is present in the region and Pgt has been isolated from aecial infections on B. vulgaris, the population is too diverse to be explained by the limited presence of B. vulgaris alone. Since 2008, we have isolated P. graminis from aecial infections on fruits of Mahonia repens and Mahonia aquifolium from northwestern United States. These two native woody shrub species, widely distributed in western North America, were once classified as resistant to P. graminis based on artificial inoculations. By isolating P. graminis from aecia, we established that M. repens and M. aquifolium along with B. vulgaris （albeit infrequent） serve as the alternate hosts ofP. graminis in the region. The isolates of P. graminis from Mahonia of North America had diverse virulence patterns and most of the isolates could be differentiated on Morocco, Line E, Chinese Spring, Little Club, LMPG-6, Rusty, and other genotypes that are considered to be universally susceptible to most Pgt isolates. This discovery explained the persistence of virulence diversity of Pgt observed in isolates derived from uredinia on cereal crops in the region. In addition to cereal crops, uredinial stage of the P. graminis population is sustained by wild grasses, especially Elymus glaucus, a native grass sharing the same habitat with the rusted Mahonia spp. Although virulence to some important stem rust resistance genes was observed in some isolates derived from Mahonia of North America when tested against single stem rust resistance gene stocks, the overall virulence is very limited in these isolates. This is likely a result of limited selection pressure on the rust population. In contrast to northwestern United Sates, the Pgt population in east of the Rocky Mountains of North America has declined steadily with a single race, QFCSC, being predominant in the last decade. This decline is likely due to a combination of factors, of which a lack of sexual recombination in the region is perhaps the most important one.

High-throughput RNA sequencing reveals differences between the transcriptomes of the five spore forms of Puccinia striiformis f.sp.tritici,the wheat stripe rust pathogen

The devastating wheat stripe(yellow)rust pathogen,Puccinia striiformis f.sp.tritici(Pst),is a macrocyclic and heteroe-cious fungus.Pst produces urediniospores and teliospores on its primary host,wheat,and pycniospores and aeciospores are produced on its alternate hosts,barberry(Berberis spp.)or mahonia(Mahonia spp.).Basidiospores are developed from teliospores and infect alternate hosts.These five spore forms play distinct roles in Pst infection,disease development,and fungal survival,etc.However,the specific genes and mechanisms underlying these functional differences are largely unknown.In this study,we performed,for the first time in rust fungi,the deep RNA sequencing to examine the transcriptomic shift among all five Pst spore forms.Among a total of 29,591 identified transcripts,951 were specifically expressed in basidiospores,whereas 920,761,266,and 110 were specific for teliospores,pycniospores,aeciospores,and urediniospores,respectively.Additionally,transcriptomes of sexual spores,namely pycniospores and basidiospores,showed significant differences from those of asexual spores(urediniospores,teliospores,and aeciospores),and transcriptomes of urediniospores and aeciospores were more similar to each other than to the three other spore forms.Especially,the basidiospores and pycniospores which infected the berberis shows wide differences in the cell wall degrading-enzymes and mating and pheromone response genes.Besides,we also found that there are 6234 differential expressed genes between the urediniospores and pycniospores,while only have 3 genes have alternative splicing enents,suggesting that differential genes expression may make more contribution than AS.This comprehensive transcriptome profiling can substantially improve our understanding of the developmental biology of the wheat stripe rust fungus.

TaARPC5 is required for wheat defense signaling in response to infection by the stripe rust fungus

Numerous studies using a combination of confocal microscopic-and pharmacological-based approaches have demonstrated that the actin cytoskeleton dynamically responds to pathogen infection.Here,we observed that phalloidin treatment induced actin nucleation,resulting in enhanced resistance of wheat against the stripe rust pathogen Puccinia striiformis f.sp.tritici(Pst).To define the mechanism underpinning this process,we characterized a family of conserved actin-binding proteins,the actin related protein(ARP)family,which controls actin polymerization.Specifically,we identified and characterized a wheat ARPC gene(Ta ARPC5),which encodes a 136-amino acid protein containing a P16-Arc domain,the smallest subunit of the ARP2/3 complex.Ta ARPC5 m RNA accumulation was induced following the infection of plants with the avirulent Pst strain,and following the elicitation with flagellin(e.g.,flg22)as well.Subcellular localization analysis revealed that Ta ARPC5 is primarily localized to the cortical actin cytoskeleton,and its precise cellular localizations suggest the proximity to processes correlated with the actin-organelle interface.Upon treatment with virulent Pst,Ta ARPC5-knockdown plants exhibited a significant reduction in the expression of PTI-specific m RNAs.Conversely,we observed enhanced induction of reactive oxygen species(ROS)accumulation and a decrease in Ta CAT1 expression following infection with an incompatible Pst isolate.Together with yeast complementation assays,the current study demonstrates a role for Ta ARPC5 in resistance signaling in wheat against Pst infection by regulating the host actin cytoskeleton.

A small knottin-like peptide negatively regulates in wheat to stripe rust resistance during early infection of wheat

Although Blufensins(Bln)have important functions in the response of plants to biotic stress the precise functioning of Bln in wheat remains largely unknown.Here we isolated a Bln gene(TaBln4)from Suwon 11 infected by Puccinia striiformis f.sp.tritici(Pst).Expression of TaBln4 increased in host plants at the early stage of infection with a virulent Pst race(CYR31)but was unchanged in response to infection by an avirulent race(CYR23).Transcription levels of TaBln4 were also regulated by hormone and abiotic stresses.Expression of TaBln4 in tobacco leaves suppressed Bax-induced programmed cell death.Knockdown of TaBln4 by virus-induced gene silencing inhibited colonization of race CYR31 by increasing the accumulation of H2O2 and formation of hypersensitive responses(HR).Transient overexpression of TaBln4 by a transient overexpression system(BSMV-VOX)increased the susceptibility of wheat to CYR31.Results from bimolecular fluorescence complementation and pull-down assays demonstrated that TaBLN4 interacted with calmodulin.Taken together,our results suggest that TaBln4 negatively regulates resistance in wheat to Pst in a reactive oxygen species(ROS)-and HR-dependent manner.

The Puccinia striiformis effector Hasp98 facilitates pathogenicity by blocking the kinase activity of wheat TaMAPK4

The obligate biotrophic fungus Puccinia striiformis f.sp.tritici(Pst)employs virulence effectors to disturb host immunity and causes devastating stripe rust disease.However,our understanding of how Pst effectors regulate host defense responses remains limited.In this study,we determined that the Pst effector Hasp98,which is highly expressed in Pst haustoria,inhibits plant immune responses triggered by flg22or nonpathogenic bacteria.Overexpression of Hasp98 in wheat(Triticum aestivum)suppressed avirulent Pst-triggered immunity,leading to decreased H2O2accumulation and promoting P.striiformis infection,whereas stable silencing of Hasp98 impaired P.striiformis pathogenicity.Hasp98 interacts with the wheat mitogenactivated protein kinase TaMAPK4,a positive regulator of plant resistance to stripe rust.The conserved TEY motif of TaMAPK4 is important for its kinase activity,which is required for the resistance function.We demonstrate that Hasp98inhibits the kinase activity of TaMAPK4 and that the stable silencing of TaMAPK4 compromises wheat resistance against P.striiformis.These results suggest that Hasp98 acts as a virulence effector to interfere with the MAPK signaling pathway in wheat,thereby promoting P.striiformis infection.

中国小麦条锈菌主要小种和流行菌系的AFLP分析

【目的】明确近年来我国小麦条锈菌主要小种及流行菌系的分子遗传关系。【方法】利用AFLP技术,对我国近年来小麦条锈菌(Puccinia striiformisf.sp.tritici)的主要流行菌系,特别是水源11类群进行了DNA指纹分析,并与毒性分析结果进行了比较。【结果】(1)小麦条锈菌流行菌系之间,无论是毒性特征还是DNA指纹特征,均存在丰富的遗传变异,但二者并不相关;(2)AFLP聚类分析显示,水源11类群的不同类型之间并没有很近的亲缘关系,其在遗传上不属于同一个来源。【结论】新出现的致病类型很可能由较近的共同起源菌系进化而来;AFLP技术非常适合于小麦条锈菌的遗传分析,能客观揭示小种(菌系)之间的亲缘关系。

小麦条锈菌Ⅲ型磷脂酰肌醇4-羟基激酶基因(PsPik1)的功能分析

【目的】克隆小麦条锈菌(Puccinia striiformis f.sp.tritici)III型磷脂酰肌醇4-羟基激酶基因(Ps Pik1),分析其在小麦条锈菌生长发育与致病过程中的作用。【方法】利用RT-PCR技术克隆Ps Pik1的c DNA序列,采用生物信息学技术分析该基因编码蛋白分子特征并构建进化树;运用实时荧光定量PCR技术,选用小麦条锈菌的延伸因子(elongation factor,EF)作为内参,明确该基因在小麦条锈菌夏孢子阶段和侵染小麦后6、12、18、24、36、48 h以及3、5、7、9、11 d共12个发育时期的表达特征;利用病毒介导的基因沉默技术(BSMV-host-induced gene silencing,BSMV-HIGS),分析沉默Ps Pik1后对小麦条锈菌生长发育及致病性的影响。通过传统酶切连接的方法构建重组载体BSMV:γ:Ps Pik1-as,利用体外转录技术获得BSMVα、β与γ3个组分,在小麦二叶一心期接种BSMV:γ:Ps Pik1-as、BSMV:γ:0-as与BSMV:γ:Ta PDS-as。接种病毒后第10天,在小麦第4叶接种条锈菌CYR32,接菌后24、48、120 h分别取样,以检测Ps Pik1的沉默效率和进行组织学观察。样品经染色处理后,统计分析接菌后48 h沉默植株与对照植株中条锈菌菌丝分支数、吸器母细胞数与菌丝长度的差异,及120 h沉默植株与对照植株中条锈菌菌落面积的差异。在接菌后12 d观察条锈病发病情况并照相记录。【结果】Ps Pik1开放阅读框(open reading frame,ORF)全长4 485 bp,编码1 494个氨基酸,具有III型磷脂酰肌醇4-羟基激酶典型的脂激酶特有结构域(LKU)、钙神经传感蛋白(NCS1)结合位点、Hom2结构域和PI3K/PI4K超家族激酶结构域。聚类分析表明,Ps Pik1聚于PI4KIIIβ类群,Ps Pik1与柄锈菌属的Pik1亲缘关系较近,与子囊菌Pik1亲缘关系次之,而与动物及植物的PI4KIIIβ亲缘关系较远。实时荧光定量PCR结果表明,Ps Pik1在接种后6、12、18、24 h呈诱导上调表达趋势,分别为夏孢子时期表达量的2.66、7.04、3.42、2.96倍,其中在12 h其表达水平最高。接种后36 h至5 d,Ps Pik1的表达水平开始下降,一直低于夏孢子表达水平,分别为夏孢子表达量的60%、30%、16%、15%。接种后7—11 d,Ps Pik1的表达量开始升高,在接种后11 d恢复至与夏孢子相当的水平。Ps Pik1基因沉默后的组织学观察分析表明,与接种BSMV:γ:0-as(对照)相比,接种BSMV:γ:Ps Pik1-as植株中条锈菌组织分化与生长发育受到了不同程度的影响,表现在接菌后48 h菌丝长度和分支数目明显减小,接菌后120 h菌落面积明显减小。沉默效率检测结果显示,在接菌后24、48、120 h,接种BSMV:γ:Ps Pik1-as植株Ps Pik1的表达水平分别仅为对照植物的49%、49%、69%,表明Ps Pik1的表达明显地受到抑制。【结论】Ps Pik1可能参与了病菌侵染初期的侵染结构分化及寄生关系的建立,在条锈菌致病过程中发挥重要作用。

Genetic Analysis and Molecular Mapping of a Stripe Rust Resistance Gene YrH9014 in Wheat Line H9014-14-4-6-1

Stripe rust, caused by Puccinia striiformis f. sp. tritici （Pst）, is one of the most widespread and destructive wheat diseases in many wheat-growing regions of the world. The winter wheat translocation line H9014-14-4-6-1 has all stage resistance. To identify stripe rust resistance genes, the segregating populations were developed from the cross between H9014-14-4-6-1 and Mingxian 169 （a wheat cultivar susceptible to all Pst races identified in China）. The seedlings of the parents and F1 plants, Fz, F3 and BC1 generations were tested with Pst races under controlled greenhouse conditions. Two genes for resistance to stripe rust were identified, one dominant gene conferred resistance to SUN11-4, temporarily designated YrH9014 and the other recessive gene conferred resistance to CYR33. The bulked segregant analysis and simple sequence repeat （SSR） markers were used to identify polymorphic markers associated with YrH9014. Seven polymorphic SSR markers were used to genotype the F2 population inoculated with SUN11-4. A linkage map was constructed according to the genotypes of seven SSR markers and resistance gene. The molecular map spanned 24.3 cM, and the genetic distance of the two closest markers Xbarc13 and Xbarc55 to gene locus was 1.4 and 3.6 cM, respectively. Based on the position of SSR marker, the resistance gene YrH9014 was located on chromosome arm 2BS. Amplification of a set of nulli-tetrasomic Chinese Spring lines with SSR marker Xbarc13 indicated that YrH9014 was located on chromosome 2B. Based on chromosomal location, the reaction patterns and pedigree analysis, YrH9014 should be a novel resistance gene to stripe rust. This new gene and flanking markers got from this study should be useful for marker-assisted selection （MAS） in breeding programs for stripe rust.

Molecular Mapping of a Stripe Rust Resistance Gene YrH9020a Transferred from Psathyrostachys huashanica Keng on Wheat Chromosome 6D

Stripe rust （yellow rust）, caused by Puccinia striiformis f. sp. tritici （Pst）, is one of the most devastating diseases of wheat throughout the world. H9020-1-6-8-3 is a translocation line originally developed from interspeciifc hybridization between wheat line 7182 and Psathyrostachys huashanica Keng and is resistant to most Pst races in China. To identify the resistance gene（s） in the translocation line, H9020-1-6-8-3 was crossed with susceptible cultivar Mingxian 169, and seedlings of the parents, F1, F2, F3, and BC1 generations were tested with prevalent Chinese Pst race CYR32 under controlled greenhouse conditions. The results indicated that there is a single dominant gene, temporarily designated as YrH9020a, conferring resistance to CYR32. The resistance gene was mapped by the F2 population from Mingxian 169/H9020-1-6-8-3. It was linked to six microsatellite markers, including Xbarc196, Xbarc202, Xbarc96, Xgpw4372, Xbarc21, and Xgdm141, lfanked by Xbarc96 and Xbarc202 with at 4.5 and 8.3 cM, respectively. Based on the chromosomal locations of these markers and the test of Chinese Spring （CS） nullitetrasomic and ditelosomic lines, the gene was assigned to chromosome 6D. According to the origin and the chromosomal location, YrH9020a might be a new resistance gene to stripe rust. The lfanking markers linked to YrH9020a could be useful for marker-assisted selection in breeding programs.

Inheritance and Molecular Mapping of Stripe Rust Resistance Gene Yr88375 in Chinese Wheat Line Zhongliang 88375

Stripe rust is one of the most important diseases of wheat worldwide. Inheritance of stripe rust resistance and mapping of resistance gene with simple sequence repeat （SSR） markers are studied to formulate efficient strategies for breeding cultivars resistant to stripe rust. Zhongliang 88375, a common wheat line, is highly resistant to all three rusts of wheat in China. The gene conferring rust disease was deduced originating from Elytrigia intermedium. Genetic analysis of Zhongliang 88375 indicated that the resistance to PST race CYR31 was controlled by a single dominant gene, temporarily designated as Yr88375. To molecular map Yr88375, a F2 segregating population consisting of 163 individuals was constructed on the basis of the hybridization between Zhongliang 88375 and a susceptible wheat line Mingxian 169; 320 SSR primer pairs were used for analyzing the genetic linkage relation. Six SSR markers, Xgwm335, Xwmc289, Xwmc810, Xgdmll6, Xbarc59, and Xwmc783, are linked to Yr88375 as they were all located on chromosome 5BL Yr88375 was also located on that chromosome arm, closely linked to Xgdmll6 and Xwmc810 with genetic distances of 3.1 and 3.9 cM, respectively. The furthest marker Xwmc783 was 13.5 cM to Yr88375. Hence, pedigree analysis of Zhongliang 88375 combined with SSR markers supports the conclusion that the highly resistance gene Yr88375 derived from Elytrigia intermedium is a novel gene for resistance to stripe rust in wheat. It could play an important role in wheat breeding programs for stripe rust resistance.

Characterization and Molecular Mapping of a Stripe Rust Resistance Gene in Synthetic Wheat CI110

Stripe rust,caused by Puccinia striiformis f.sp.tritici（Pst）,is one of the most destructive diseases of wheat（Triticum aestivum L.）.To diversify stripe rust-resistant resources for wheat breeding programs,a CIMMYT synthetic wheat line CI110 was identified to be resistant to 28 isolates of Pst,including 6 Chinese prevalent races CYR28-CYR33.Genetic analysis indicated that a single dominant gene was responsible for the stripe rust resistance in CI110,temporarily designated YrC110.A molecular map,harboring YrC110 and 9 linked SSR markers,was constructed through simple sequence repeat（SSR）,and bulked segregant analysis.These linked markers and YrC110 were assigned on the short arm of chromosome 1B using the Chinese Spring nullisomic-tetrasomic and ditelosomic stocks.Gene postulation based on seedling reaction patterns to 30 Pst isolates suggested that the resistance gene YrC110 seemed different from the other known resistance genes tested,such as Yr9,Yr10,Yr15,Yr24,and Yr26/YrCH42.Four SSR markers Xbarc187150,Xgwm18227,Xgwm11223,and Xbarc240292 distinguished YrC110 from Yr10,Yr15,Yr24,and Yr26/YrCH42,and could be used as diagnostic ones for YrC110 in wheat resistant breeding programs against stripe rust.