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.

Wheat stripe rust resistance gene Yr24/Yr26：A retrospective review

The objective of this review is to describe events in China and elsewhere that are related to the discovery, genetic identification, use, and ultimate break-down of a single wheat gene for resistance to stripe rust, namely Yr24/Yr26. In our retrospective analysis there was an early assumption of at least three genes at or near the locus, which caused an erroneous presumption of genetic diversity for resistance. It is an example of another boom and bust cycle in plant breeding with races virulent to Yr26(V26 races) now being the majority race group in the Chinese Pst population. We have attempted to present our story in a historical and personal context demonstrating research inputs from different national and international groups, as well as some significant contemporary side issues. It covers the period from the late 1980 s to 2017, during which significant rapid advances in the molecular biology of host: pathogen genetics occurred. We attempt to describe both successes and drawbacks in our work.

Haplotype variations in QTL for salt tolerance in Chinese wheat accessions identified by marker-based and pedigree-based kinship analyses

Most modern wheat cultivars were selected on the basis of yield-related indices measured under optimal fertilizer and irrigation inputs.With climate change,land degradation and salinity caused by sea water encroachment,wheat is increasingly subjected to environmental stress.Moreover,expanding urbanization increasingly encroaches upon prime agricultural land in countries like China,and alternative cropping areas must be found.Some of these areas have moderate constraining factors,such as salinity.Therefore,it is important to investigate whether current genetic materials and breeding procedures are maintaining adequate variability to address future problems caused by abiotic stress.In this study,a panel of 307 wheat accessions,including local landraces,exotic cultivars used in Chinese breeding programs and Chinese cultivars released during different periods since1940,were subjected to a genome-wide association study to dissect the genetic basis of salinity tolerance.Both marker-based and pedigree-based kinship analyses revealed that favorable haplotypes were introduced in some exotic cultivars as well as a limited number of Chinese landraces from the 1940 s.However,improvements in salinity tolerance during modern breeding are not as obvious as that of yield.To broaden genetic diversity for increasing salt tolerance,there is a need to refocus attention on local landraces that have high degrees of salinity tolerance and carry rare favorable alleles that have not been exploited in breeding.

Understanding the lifestyles and pathogenicity mechanisms of obligate biotrophic fungi in wheat:The emerging genomics era

Obligate biotrophic fungi cause serious and widespread diseases of crop plants, but are challenging to investigate because they cannot be cultured in vitro. The two economically important groups of biotrophic fungi parasitizing wheat are the rust and powdery mildew pathogens, but their obligate biotrophic lifestyles and pathogenicity mechanisms are not well understood at the molecular level. With the advent of next generation sequencing technology, increasing numbers of pathogen genomes are becoming available. Research in plant pathology has entered a new genomics era. This review summarizes recent progress in understanding the biology and pathogenesis of biotrophic fungal pathogens attacking wheat based on pathogen genomics. We particularly focus on the three wheat rust and the powdery mildew fungi in regard to genome sequencing, avirulence gene cloning, effector discovery, and pathogenomics. We predict that coordinated study of both wheat and its pathogens should reveal new insights in biotrophic adaptation, pathogenicity mechanisms,and population dynamics of these fungi that will assist in development of new strategies for breeding wheat varieties with durable resistance.

SNP-based linkage mapping for validation of adult plant stripe rust resistance QTL in common wheat cultivar Chakwal 86

Wheat crops in China are constantly challenged by stripe rust. Deployment of cultivars with diverse resistances is the best strategy to control the disease. A recombinant inbred line(RIL) population derived from a cross between the resistant cultivar Chakwal 86 and susceptible landrace Mingxian 169 was studied in multiple environments to examine the underlying genetics and to identify quantitative trait loci(QTL) for stripe rust resistance.One hundred and twenty-eight RILs were genotyped with wheat 35 K SNP array and a genome-wide linkage map with 1480 polymorphic SNP markers, or bins, was constructed.Two major QTL on chromosomes 1BL and 3BS, and one minor QTL on 6BS had significant effects in reducing stripe rust severity. The QTL were validated using composite interval mapping(CIM) and inclusive composite interval mapping(ICIM). These methods explained59.0%–74.1% of the phenotype variation in disease response. The QTL on chromosome 1 BL was confirmed to be Yr29/Lr46 and the one on 3BS was the resistance allele identified in CIMMYT germplasm but was not Yr30/Sr2. The QTL on 6BS probably corresponded to previously known QTL. RILs with combined QTL were more resistant than those with single or no QTL. Kompetitive allele-specific PCR(KASP) assays for the QTL with largest effect QTL on chromosome 3BS were performed on a subset of RILs and 150 unrelated wheat lines. The QTL on 3BS with its linked KASP markers can be used in marker-assisted selection to improve stripe rust resistance in breeding programs.

Combined linkage and association mapping reveals two major QTL for stripe rust adult plant resistance in Shaanmai 155 and their haplotype variation in common wheat germplasm

The development and deployment of diverse resistance sources in new wheat cultivars underpin the durable control of stripe rust.In the present study,two loci for adult plant resistance(APR),QYr SM155.1 and QYr SM155.2,were identified in the Chinese wheat breeding line Shaanmai 155.QYr SM155.1 was mapped to a 3.0-c M interval between the single-nucleotide polymorphism(SNP)markers AX-109583610 and AX-110907562 on chromosome arm 2 BL.QYr SM155.2 was mapped to a 2.1-c M interval flanked by the SNP markers AX-110378556 and AX-86173526 on chromosome arm 7 AS.A genome-wide association study was used to identify markers associated with APR in a panel of 411 spring wheat lines.Thirteen and 11 SNPs were significantly associated with QYr SM155.1 and QYr SM155.2,respectively,corresponding to physical intervals of 653.75–655.52 Mb on 2 BL and 81.63–83.93 Mb on7 AS.To characterize the haplotype variation and the distribution of these QTL,haplotype analysis was performed based on these SNPs in an independent panel of 1101 worldwide wheat accessions.Three major haplotypes(2 B_h1,2 B_h2,and 2 B_h3)for QYr SM155.1 and four major haplotypes(7 A_h1,7 A_h2,7 A_h3,and 7 A_h4)for QYr SM155.2 were identified.Accessions individually harboring QYr SM155.1_h1 and QYr SM155.2_h1 haplotypes and their combination displayed resistance.Additional assays of 1306 current Chinese cultivars and breeding lines using markers flanking QYr SM155.1 and QYr SM155.2 indicated that the resistance haplotypes of the two QTL were present in respectively 1.45%and 14.16%of lines.Increasing resistance haplotype frequencies at these two loci using marker-assisted selection should benefit wheat production in China.

CaREM1.4 interacts with CaRIN4 to regulate Ralstonia solanacearum tolerance by triggering cell death in pepper

Remorins,plant-specific proteins,have a significant role in conferring on plants the ability to adapt to adverse environments.However,the precise function of remorins in resistance to biological stress remains largely unknown.Eighteen CaREM genes were identified in pepper genome sequences based on the C-terminal conserved domain that is specific to remorin proteins in this research.Phylogenetic relations,chromosomal localization,motif,gene structures,and promoter regions of these remorins were analyzed and a remorin gene,CaREM1.4,was cloned for further study.The transcription of CaREM1.4 in pepper was induced by infection with Ralstonia solanacearum.Knocking down CaREM1.4 in pepper using virus-induced gene silencing(VIGS)technologies reduced the resistance of pepper plants to R.solanacearum and downregulated the expression of immunity-associated genes.Conversely,transient overexpression of CaREM1.4 in pepper and Nicotiana benthamiana plants triggered hypersensitive response-mediated cell death and upregulated expression of defense-related genes.In addition,CaRIN4-12,which interacted with CaREM1.4 at the plasma membrane and cell nucleus,was knocked down with VIGS,decreasing the susceptibility of Capsicum annuum to R.solanacearum.Furthermore,CaREM1.4 reduced ROS production by interacting with CaRIN4-12 upon co-injection in pepper.Taken together,our findings suggest that CaREM1.4 may function as a positive regulator of the hypersensitive response,and it interacts with CaRIN4-12,which negatively regulates plant immune responses of pepper to R.solanacearum.Our study provides new evidence for comprehending the molecular regulatory network of plant cell death.

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.

Using UAV-Based Temporal Spectral Indices to Dissect Changes in the Stay-Green Trait in Wheat

Stay-green(SG)in wheat is a beneficial trait that increases yield and stress tolerance.However,conventional phenotyping techniques limited the understanding of its genetic basis.Spectral indices(SIs)as non-destructive tools to evaluate crop temporal senescence provide an alternative strategy.Here,we applied Sls to monitor the senescence dynamics of 565 diverse wheat accessions from anthesis to maturation stages over 2 field seasons.Four Sis(normalized difference vegetation index,green normalized difference vegetation index,normalized difference red edge index,and optimized soil-adjusted vegetation index)were normalized to develop relative stay-green scores(RSGS)as the SG indicators.An RSGS-based genome-wide association study identified 47 high-confidence quantitative trait loci(QTL)harboring 3,079 single-nucleotide polymorphisms associated with SG and 1,085 corresponding candidate genes.Among them,15 QTL overlapped or were adjacent to known SG-related QTL/genes,while the remaining QTL were novel.Notably,a set of favorable haplotypes of SG-related candidate genes such as TraesCS2A03G1081100,TracesCS6B03G0356400,and TracesCS2B03G1299500 are increasing following the Green Revolution,further validating the feasibility of the pipeline.This study provided a valuable reference for further quantitative SG and genetic research in diverse wheat panels.

Pan-genome analysis reveals a highly plastic genome and extensive secreted protein polymorphism in Puccinia striformis f.sp.tritici

The obligate biotrophic basidiomycete fungus Puccinia striformis f.sp.tritici(Pst)is the causative agent of wheat stripe(yellow)rust,a disease that results in severe damage to global wheat production(Chen and Kang,2017).This pathogen has a mixed reproductive mode encompassing both asexual and sexual reproduction.The asexual stage is accomplished by reinfecting wheat with urediniospores,while the sexual cycle involves five different spore types and two phylogenetically unrelated plant hosts wheat,which is the primary host,and barberry,which is the alternate host(Zhao et al.,2016).This extremely complex lifecycle facilitates large genetic variation among Pst populations,which is conducive to the emergence of new virulent races that can overcome wheat resistance genes,resulting in epidemics(Chen and Kang,2017).Secreted effector proteins,the key virulence factors in fungal pathogens,can not only suppress plant immune systems but also trigger host immune responses following recognition by plant receptors(Toruno et al.,2016).

The Stripe Rust Resistance Gene Yr10 Encodes an Evolutionary-Conserved and Unique CC-NBS-LRR Sequence in Wheat

The first seedling or all-stage resistance （R） R gene against stripe rust isolated from Moro wheat （Triticum aes- tivum L.） using a map-based cloning approach was identified as Yr10. Clone 4B of this gene encodes a highly evolutionary- conserved and unique CC-NBS-LRR sequence. Clone 4E, a homolog of Yr10, but lacking transcription start site （TSS） and putative TATA-box and CAAT-box, is likely a non-expressed pseudogene. Clones 4B and 4E are 84% identical and divergent in the intron and the LRR domain. Gene silencing and transgenesis were used in conjunction with inoculation with differen- tially avirulent and virulent stripe rust strains to demonstrate Yr10 functionality. The Yr10 CC-NBS-LRR sequence is unique among known CC-NBS-LRR R genes in wheat but highly conserved homologs （E = 0.0） were identified in Aegilops tauschii and other monocots including Hordeum vulgare and Brachypodium distachyon. Related sequences were also identified in genomic databases of maize, rice, and in sorghum. This is the first report of a CC-NBS-LRR resistance gene in plants with limited homologies in its native host, but with numerous homologous R genes in related monocots that are either host or non-hosts for stripe rust. These results represent a unique example of gene evolution and dispersion across species.

Stripe Rust Effector PstGSRE1 Disrupts Nuclear Localization of ROS-Promoting Transcription Factor TaLOL2 to Defeat ROS-Induced Defense in Wheat

Puccinia striiformis f.sp.tritici(Pst),a biotrophic plant pathogen,secretes numerous effectors to modulate host defense systems.Understanding the molecular mechanisms by which Pst effectors regulate wheat immunity is of great importance for the development of novel strategies for durable control of stripe rust.In this study,we identified a glycine-serine-rich effector gene,PstGSRE1,which is highly induced dur-ing early infection.Transgenic expression of PstGSRE1 RNAi constructs in wheat significantly reduced virulence of Pst and increased H2O2 accumulation in wheat.PstGSRE1 was shown to target the reactive ox-ygen species(ROS)-associated transcription factor TaLOL2,a positive regulator of wheat immunity.PstGSRE1 disrupted nuclear localization of TaLOL2 and suppressed ROS-mediated cell death induced by TaLOL2,thus compromising host immunity.This work reveals a previously unrecognized strategy whereby rust fungi exploit the PstGSRE1 effector to defeat ROS-associated plant defense by modulating the subcellular compartment of a host immune regulator and facilitate pathogen infection.

Variation in cis-regulation of a NAC transcription factor contributes to drought tolerance in wheat

Drought is a major environmental factor limiting wheat production worldwide,and developing drought-tolerant cultivars is a central challenge for wheat breeders globally.Therefore,it is important to identify genetic components determining drought tolerance in wheat.In this study,we identified a wheat NAC gene(TaNAC071-A)that is tightly associated with drought tolerance by a genome-wide association study.Knockdown of TaNAC071-A in wheat attenuated plant drought tolerance,whereas its overexpression significantly enhanced drought tolerance through improved water-use efficiency and increased expression of stress-responsive genes.This heightened water-saving mechanism mitigated the yield loss caused by water deficit.Further candidate gene association analysis showed that a 108-bp insertion in the promoter of TaNAC071-A alters its expression level and contributes to variation in drought tolerance among wheat accessions.This insertion contains two MYB cis-regulatory elements(CREs)that can be directly bound by the MYB transcription activator,TaMYBL1,thereby leading to increased TaNAC071-A expression and plant drought tolerance.Importantly,introgression of this 108-bp insertion allele,TaNAC071-AIn-693,into drought-sensitive cultivars could improve their drought tolerance,demonstrating that it is a valuable genetic resource for wheat breeding.Taken together,our findings highlight a major breakthrough in determining the genetic basis underlying phenotypic variation in wheat drought tolerance and showcase the potential of exploiting CRE-containing indels for improving important agronomical traits.

WheatOmics:A platform combining multiple omics data to accelerate functional genomics studies in wheat

Dear Editor,Mold-breaking progress in whole-genome sequencing and rapid accumulation of multi-omics data have revolutionized the research strategies of functional genomics in wheat(Wang et al.,2018).However,how to access these vast multi-omics data and to extract key information on genes of in-terest,is still challenging for most wet-lab or field wheat re-searchers who have little bioinformatic experiences and cannot access the expensive computational resources.Here,we pre-sent WheatOmics(http://wheatomics.sdau.edu.cn/,previously designated as Triticeae Multi-omics Center,http://202.194.139.32/),a free,web-accessible,and user-friendly platform.WheatOmics not only empowers the effective access to the visualized multi-omics data of user-interested genes but also offers several distinctive and practical toolkits that can ease almost every aspect of wheat functional genomics studies(Figure 1A).

YR36/WKS1-Mediated Phosphorylation of PsbO,an Extrinsic Member of Photosystem Ⅱ,Inhibits Photosynthesis and Confers Stripe Rust Resistance in Wheat

Wheat stripe rust,due to infection by Puccinia striiformis f.sp.tritici(Pst),is a devastating disease that causes significant global grain yield losses.Yr36,which encodes Wheat Kinase START1(WKS1),is an effec-tive high-temperature adult-plant resistance gene and confers resistance to a broad spectrum of Pst races.We previously showed that WKS1 phosphorylates the thylakoid ascorbate peroxidase protein and reduces its ability to detoxify peroxides,which may contribute to the accumulation of reactive oxygen species(ROS).WKS1-mediated Pst resistance is accompanied by leaf chlorosis in Pst-infected regions,but the un-derlying mechanisms remain elusive.Here,we show that WKS1 interacts with and phosphorylates PsbO,an extrinsic member of photosystem Ⅱ(PS Ⅱ),to reduce photosynthesis,regulate leaf chlorosis,and confer Pst resistance.A point mutation in PsbO-A1 or reduction in its transcript levels by RNA interference resulted in chlorosis and reduced Pst sporulation.Biochemical analyses revealed that WKS1 phosphorylates PsbO at two conserved amino acids involved in physical interactions with PS Ⅱ and reduces the binding affinity of PsbO with PS Ⅱ.Presumably,phosphorylated PsbO proteins dissociate from the PS Ⅱ complex and then un-dergo rapid degradation by cysteine and aspartic proteases.Taken together,these results demonstrate that perturbations of wheat PsbO by point mutation or phosphorylation by WKS1 reduce the rate of photo-synthesis and delay the growth of Pst pathogen before the induction of ROS.

A novel wheat NAC transcription factor,Ta NAC_(30), negatively regulates resistance of wheat to stripe rust

NAC transcription factors are widespread in the plant kingdom and play essential roles in the transcriptional regulation of defense responses. In this study, we isolated a novel NAC transcription factor gene, TaNAC30, from a cDNA library constructed from wheat （Triticum aestivum） plants inoculated with the stripe rust pathogen Puccinia striiformis f. sp. tritici （Pst）. TaNAC30 contains a typical NAM domain and localizes to the nucleus. Yeast one-hybrid assays revealed that TaNAC30 exhibits transcriptional activity and that its C-terminus is necessary for the activation of transcription. Expression of TaNAC30 increased when host plants were infected with a virulent race （CYR31） of the rust fungus Pst. Silencing of TaNAC30 by virus-induced gene silencing inhibited colonization of the virulent Psi isolate CYR31. Moreover, detailed histological analyses showed that silencing of TaNAC30 enhanced resistance to Pst by inducing a significant increase in the accumulation of H2O2. Finally, we overexpressed TaNAC30 in fission yeast and determined that cell viability was severely reduced in TaNAC30-transformed cells grown on medium containing H2O2. These results suggest that TaNAC30 negatively regulates plant resistance in a compatible wheat-Psi interaction.

Gene expression profiling of Puccinia striiformis f.sp.tritici during development reveals a highly dynamic transcriptome

Puccinia striiformis f. sp. tritici （PsO causes stripe rust, one of the most important diseases of wheat worldwide, cDNA libraries had been constructed from urediniospores, germinated urediniospores and haustoria. However, little is known about the expression patterns of the genes related to the infection process and sporulation of the pathogen. In this study, a custom oligonucleotide microarray was constructed using sequences of 442 gene transcripts selected from Pst cDNA libraries. The expression patterns of the genes were determined by hybridizing the microarray with cDNA from Pst in vitro and Pst-infected wheat leaves. The time course study identified 55 transcripts that were differentially expressed during the infection process in a compatible interaction. They were identified to have functions related to the following biological processes, including carbohydrate and lipid metabolism, energy, cell signaling, protein synthesis, cell structure and division. In an incompatible interaction, 17 transcripts of the pathogen were differentially expressed in resistant wheat leaves inoculated with an avirulent Pst race, ten of which had similar expression patterns to those in the compatible interaction. Several candidates for pathogenicity and virulence/avirulence related genes were also identified. The results of quantitative real-time PCR validated the expression patterns of some selected genes. The study demonstrates that the custom oligonucleotide microarray technology is useful to determine the expression patterns of the pathogen genes involved in different types of the host--pathogen interactions and stages of development.

WHEAT STRIPE RUST AND INTEGRATION OF SUSTAINABLE CONTROL STRATEGIES IN CHINA

Stripe (yellow) rust caused by Puccinia striiformis f. sp. tritici occurs in almost allwheat-producing regions of the world. Severe countrywide epidemics in Chinahave caused substantial yield losses. Growing resistant cultivars is the beststrategy to control this disease but the pathogen can overcome resistance inwheat cultivars. The high variation in the virulence of the pathogen combinedwith the large areas of susceptible wheat cultivars enables the pathogenpopulation to increase rapidly and disperse over long distances under favorableenvironmental conditions, resulting in severe pandemics within croppingseasons. Current stripe rust control measures are based on many years ofresearch including the underlying epidemiology regarding year-to-year survivalof the pathogen, pathways of pathogen dispersal within seasons and years, therole of P. striiformis sexual hybridization, the use of resistance sources inbreeding programs, and year-round surveillance of national wheat crops that arepresent in different parts of the country throughout the year. All these strategiesdepend on accurate prediction of epidemics, more precise use of fungicides tomeet national requirements and better deployment of resistance genes. Newideas with potential application in sustainable protection of stripe rust includenegative regulatory gene editing, resistance gene overexpression and biologicalcontrol based on microbiomes.

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.