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.

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.

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.

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.

Determination of heterozygosity for avirulence/virulence loci through sexual hybridization of Puccinia striiformis f. sp. tritici

Wheat stripe rust caused by Puccinia striiformis f. sp. tritici is one of the most devastating diseases of wheat worldwide and resistant cultivars are vital for its management. Therefore, investigating the heterozygosity of the pathogen is important because of rapid virulence changes in isolates heterozygous for avirulence/virulence.An isolate of P. striiformis f. sp. tritici was selfed on Berberis shensiana to determine the heterozygosity for avirulence/virulence loci. One hundred and twenty progeny isolates obtained from this selfing were phenotyped using 25 lines of wheat containing Yrgenes and genotyped with 96 simple sequencing repeat markers, with51 pathotypes and 55 multi-locus genotypes being identified. All of these were avirulent on lines with Yr5,Yr10, Yr15, Yr24 and Yr26 and virulent on lines with Yr17,Yr25 and YrA, indicating that the parental isolate was homozygously avirulent or homozygously virulent for these loci. Segregation was found for wheat lines with Yr1,Yr2, Yr4, Yr6, Yr7, Yr8, Yr9, Yr27, Yr28, Yr32, Yr43, Yr44,YrExp2, YrSp, YrTr1, YrTye and YrV23. The 17 cultivars to which the Pst was identified as heterozygous with respect to virulence/avirulence should not be given priority in breeding programs to obtain new resistant cultivars.

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.

Comments on “Determination of heterozygosity for avirulence/virulence loci through sexual hybridization of Puccinia striiformis f. sp. tritici”

Over the past decades Puccinia striiformis f.sp.tritici（Pst）has developed into one of the most,if not the most important fungal pathogen in wheat production worldwide.In China,Pst has caused numerous epidemics with partially devastating yield losses[1].The occurrence of the'warrior'race in Europe in 2011 also caused significant problems[2].Pst,like other obligate biotrophs,is characterized by a high degree of genetic variability,especially with respect

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.

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.

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.

Mapping of wheat stripe rust resistance gene Yr041133 by BSR-Seq analysis

Puccinia striiformis Westend. f. sp. tritici(Pst) pathotype CYR34 is widely virulent and prevalent in China.Here, we report identification of a strpie rust resistance(Yr) gene, designated Yr041133, in winter wheat line 041133. This line produced a hypersensitive reaction to CYR34 and conferred resistance to 13 other pathotypes. Resistance to CYR34 in line 041133 was controlled by a single dominant gene. Bulked segregant RNA sequencing(BSR-Seq) was performed on a pair of RNA bulks generated by pooling resistant and susceptible recombinant inbred lines. Yr041133 was mapped to a 1.7 c M genetic interval on the chromosome arm 7 BL that corresponded to a 0.8 Mb physical interval(608.9–609.7 Mb) in the Chinese Spring reference genome. Based on its unique physical location Yr041133 differred from the other Yr genes on this chromosome arm.

Effects of UV-B radiation intensity and timing on epidemiological components of wheat stripe rust

Stripe rust caused by Puccinia striiformis f. sp. tritici is an important wheat disease worldwide that is greatly influenced by environmental conditions. Ultraviolet B(UV-B) radiation is one important environmental factor affecting the occurrence and epidemiology of wheat stripe rust. Investigating UV-B radiation effects on the epidemiology of stripe rust may be conducive to monitoring and predicting this disease. In this study, wheat seedlings were exposed to UV-B radiation during different periods under laboratory conditions and radiation effects on epidemiological components of wheat stripe rust were investigated. Results showed that incubation period was shortened, and the infection efficiency, sporulation quantity and disease index increased when UV-B radiation was performed only pre-inoculation. When the UV-B radiation was performed only postinoculation or both pre-and post-inoculation, the incubation period was prolonged, and the infection efficiency, sporulation quantity and disease index were reduced. When healthy wheat seedlings were inoculated using urediospores collected from wheat leaves irradiated by UV-B only post-inoculation or both pre-and post-inoculation, infection efficiency, sporulation quantity and disease index were also reduced. However, in the latter, the disease incubation period did not differ under varying UV-B radiation intensities compared to that when wheat leaves were not treated with UV-B radiation. Overall, the effects of direct exposure of wheat plants to UV-B radiation with different intensities in different periods on epidemiological components of wheat stripe rust were systematically explored, and the results suggest that the effects of UV-B radiation increased gradually with the increase of UV-B radiation intensity. This information provides a basis for monitoring and predicting this disease as well as for conducting further studies on pathogen virulence variation.

Genetics and Molecular Mapping of a High-Temperature Resistance Gene to Stripe Rust in Seeding-Stage in Winter Wheat Cultivar Lantian 1

Stripe rust, caused by Puccinia striiformis Westend. f. sp. tritici （Pst）, is a severe foliar disease of common wheat （Triticum aestivum L.） in the world. Resistance is the best approach to control the disease. The winter wheat cultivar Lantian 1 has high-temperature resistance to stripe rust. To determing the gene（s） for the stripe rust resistance, Lantian 1 was crossed with Mingxian 169 （M169）. Seedlings of the parents, and F 1 , F 2 and F 2-3 progenies were tested with races CYR32 of Pst under controlled greenhouse conditions. Lantian 1 has a single partially dominant gene conferred resistance to race CYR32, designated as YrLT1. Simple sequence repeat （SSR） techniques were used to identify molecular markers linked to YrLT1. A linkage group of five SSR markers was constructed for YrLT1 using 166 F 2 plants. Based on the SSR marker consensus map and the position on wheat chromosome, the resistance gene was assigned on chromosome 2DL. Amplification of a set of nulli-tetrasomic Chinese Spring lines with SSR marker Xwmc797 confirmed that the resistance gene was located on the long arm of chromosome 2D. Because of its chromosomal location and the high-temperature resistance, this gene is different from previously described genes. The molecular map spanned 29.9 cM, and the genetic distance of two close markers Xbarc228 and Xcfd16 to resistance gene locus was 4.0 and 5.7 cM, respectively. The polymorphism rates of the flanking markers in 46 wheat lines were 2.1 and 2.1%, respectively; and the two markers in combination could distinguish the alleles at the resistance locus in 97.9% of tested genotypes. This new gene and flanking markers should be useful in developing wheat cultivars with high level and possible durable resistance to stripe rust.

Genetic analysis of adult plant,quantitative resistance to stripe rust in wheat landrace Wudubaijian in multi-environment trials

Stripe rust,caused by Puccinia striiformis f.sp.tritici(Pst),is one of the most destructive diseases on wheat worldwide.Wudubaijian,a wheat landrace released from Gansu Province in China since 1950,exhibits adult-plant resistance to stripe rust for several decades.To elucidate the genetic basis of stripe rust resistance,Wudubaijian was crossed with the high susceptible cultivar Mingxian 169,and stripe rust tests of both parents and the F2:3 lines were conducted in four environments of Yangling and Tianshui in 2015 and 2016,respectively.The relative area under disease progress curve(rAUDPC)of Mingxian 169/Wudubaijian F_(2:3) lines showed that the resistance of Wudubaijian was controlled by quantitative trait loci(QTL).Combined with phenotypic data and molecular markers,two stable QTLs were identified in Wudubaijian.QYrwdbj.nwafu-5A with the phenotypic variance of 15.02-40.26% was located between 5AS1-0.40-0.75 and 5AS3-0.75-0.98 of chromosome 5AS,and QYrwdbj.nwafu-2B.1 with the phenotypic variance of 9.54-10.40%was located in the bin C-2BS1-0.53 of chromosome 2BS.Through the location of flanking markers and epistasis analysis,QYrwdbj.nwafu-5A may be a new major QTL that can be used in conjunction with other stripe rust resistance genes(QTLs).

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.

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.