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AbstractWinter wheat production in Canada is approximately 5% of all the wheat seeded in Canada; however, it has important economic and agronomic benefits for growers. Stripe rust of wheat, caused by Puccinia striiformis f. sp. tritici Eriks. occurs across western Canada in many years; as a result, it is prudent to evaluate strategies to control stripe rust in winter wheat. The objective of this project was to evaluate the effects of fall and spring fungicide application (metconazole and pyraclostrobin) on stripe rust, as well as leaf spot severity, and impact on yield and quality of winter wheat (Triticum aestivum L.). The effect of fungicide application in the fall, in the spring, or both, on four winter wheat cultivars varying in resistance to these diseases was evaluated at 11 site-years in Alberta and Saskatchewan for four growing seasons from 2013 to 2017. Stripe rust severity on the susceptible cultivars, ‘AC Bellatrix’ and ‘CDC Osprey’, and leaf spot severity on these cultivars and ‘Radiant’, was reduced by single spring or dual (fall and spring) applications, but not by fall application alone when disease severity was high. Single spring and dual fungicide applications to ‘AC Bellatrix’ maintained yield potential by 16.9–229.5% compared to the unsprayed treatment. Grain quality was also maintained by the same treatments at some site-years. During the study, virulence of the natural Pst population on ‘Radiant’ with the Yr10 resistance gene was differentially expressed among sites and therefore yield response to fungicide varied. The stripe rust resistant cultivar ‘Moats’ did not benefit from fungicide application at any timing. Single fall fungicide application had no effect on disease severity of any of the cultivars at any site-years, although it had minor effects on yield or grain quality of ‘AC Bellatrix’ at a few site-years. Multiple fungicide applications, in fall and again in spring, did not offer additional benefits to a single spring application. [ABSTRACT FROM AUTHOR]

Summary: Mitochondria‐induced cell death is closely correlated with plant immune responses against pathogens. However, the molecular mechanisms by which pathogens manipulate mitochondria to suppress host resistance remain poorly understood.In this study, a haustorium‐specific effector Pst11215 from the wheat stripe rust pathogen Puccinia striiformis f. sp. tritici (Pst) was characterized by host‐induced gene silencing. The interaction partners regulated by Pst11215 were screened using the yeast two‐hybrid system. In addition, Pst11215‐mediated immune regulation modes were further determined.The results showed that Pst11215 was required for Pst virulence. Pst11215 interacted with the wheat voltage‐dependent anion channel TaVDAC1, the negative regulator of wheat resistance to stripe rust, in mitochondria. Furthermore, the E3 ubiquitin ligase TaVDIP1 targeted and ubiquitinated TaVDAC1, which can be promoted by Pst11215. TaVDIP1 conferred enhanced wheat susceptibility to Pst by cooperating with TaVDAC1. Overexpression of TaVDIP1 reduced reactive oxygen species (ROS) accumulation and abnormal mitochondria.Our study revealed that Pst11215 functions as an important pathogenicity factor secreted to the host mitochondria to compromise wheat resistance to Pst possibly by facilitating TaVDIP1‐mediated ubiquitination of TaVDAC1, thereby protecting mitochondria from ROS‐induced impairment. This research unveils a novel regulation mode of effectors hijacking host mitochondria to contribute to pathogen infection. [ABSTRACT FROM AUTHOR]

Worldwide food security is severely threatened by the devastating wheat stripe rust disease. The utilization of resistant wheat cultivars represents the most cost‐effective and efficient strategy for combating this disease. However, the lack of resistant resources has been a major bottleneck in breeding for wheat disease resistance. Therefore, revealing novel gene resources for combating stripe rust and elucidating the underlying resistance mechanism is of utmost urgency. In this study, we identified that the soybean NF‐YB transcription factor GmNF‐YB20 in wheat provides resistance to the stripe rust fungus (Puccinia striiformis f. sp. tritici, Pst). Wheat lines with stable overexpression of the GmNF‐YB20 enhanced resistance against multiple Pst races. Transcriptome profiling of GmNF‐YB20 transgenic wheat under Pst infection unveiled its involvement in the lipid signaling pathway. RT‐qPCR assays suggested that GmNF‐YB20 increased transcript levels of multiple nonspecific lipid transfer protein (LTP) genes during wheat‐Pst interaction, luciferase reporter analysis illustrates that it activates the transcription of TaLTP1.50 in wheat protoplast, and GmNF‐YB20 overexpressed wheat plants had higher total LTP content in vivo during Pst infection. Overexpression of TaLTP1.50 in wheat significantly increased resistance to Pst, whereas knockdown of TaLTP1.50 exhibited the opposite trends, indicating that TaLTP1.50 plays a positive role in wheat resistance. Taken together, our findings provide perspective regarding the molecular mechanism of GmNF‐YB20 in wheat and highlight the potential use for wheat breeding. Summary statement: The soybean transcription factor GmNF‐YB20 confers resistance to stripe rust in transgenic wheat by regulating nonspecific lipid transfer protein genes. Our findings provide perspective regarding the molecular mechanism of GmNF‐YB20 in wheat and highlight the potential use for wheat breeding. [ABSTRACT FROM AUTHOR]

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Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most destructive wheat diseases. The plant hormone abscisic acid (ABA) plays a key regulatory role in plant response to stress. ABA‐, stress‐, ripening‐induced proteins (ASR) have been shown to be abundantly induced in response to biotic and abiotic stresses to protect plants from damage. However, the function of wheat ASR2‐like protein (TaASR2L) in plants under biotic stress remains unclear. In this study, transient silencing of TaASR2L using a virus‐induced gene silencing system substantially reduced wheat resistance to Pst. TaASR2L interaction with serine/arginine‐rich splicing factor SR30‐like (TaSR30) was validated mainly in the nucleus. Knockdown of TaSR30 expression substantially reduced wheat resistance to Pst. Overexpression of TaASR2L and TaSR30 demonstrated that they can promote the expression of ABA‐ and resistance‐related genes to enhance wheat resistance to Pst. In addition, the expression levels of TaSR30 and TaASR2L were substantially increased by exogenous ABA, and the resistance of wheat to Pst was increased, and the expression of PR genes was induced. Therefore, these results suggest that TaASR2L interacts with TaSR30 by promoting PR genes expression and enhancing wheat resistance to Pst. [ABSTRACT FROM AUTHOR]

Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), significantly impacts global wheat production, including China. Monitoring Pst virulence is crucial for disease management. This study used 18 Yr single‐gene isogenic lines of wheat to characterize the virulence of 2023 Pst collections in China. A total of 103 isolates were collected from 11 provinces, and 61 races were identified. Frequencies of virulence to the 18 Yr genes varied from 0% to 95.1%, with low frequencies (defined as less than 10%) to Yr85 (7.8%) and Yr10 (8.7%); moderate frequencies (10%–40%) to Yr24 (15.5%), Yr32 (16.5%), YrSP (37.9%) and Yr76 (37.9%); and high frequencies (>40%) to Yr7 (47.6%), Yr1 (68.0%), Yr9 (69.9%), Yr27 (69.9%), Yr17 (79.6%), Yr6 (89.3%), YrExp2 (92.2%), Yr43 (93.2%), Yr8 (95.1%) and Yr44 (95.1%). Yr6, Yr8, Yr17, Yr27, Yr43, Yr44 and YrExp2 have almost lost their effectiveness in all provinces, while Yr10, Yr24, Yr32 and Yr85 are effective in Hebei, Shandong, Shaanxi, Gansu and Anhui. No isolate was virulent to Yr5 or Yr15, indicating their effectiveness against Pst populations in China. The Pst isolates had a wide virulence spectrum ranging from 3 to 16 virulence factors, with an average of 9.5. Comparing 2023 to 2021, the PstCN‐040 and races sharing virulence to Yr1, Yr6, Yr7, Yr8, Yr9, Yr17, Yr43, Yr44 and YrExp2 predominated, with frequencies 16.4% and 25.2%. This study provides valuable information on the virulence composition of Pst populations in China, helping to guide the development of genetic resistance for wheat in China. [ABSTRACT FROM AUTHOR]

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 newly-emerged 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 (PTSA-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.

Abstract Protein phosphorylation plays an important role in immune signaling transduction in plant resistance to pathogens. Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), severely devastates wheat production. Nonetheless, the molecular mechanism of wheat resistance to stripe rust remains limited. In this study, quantitative phosphoproteomics was employed to investigate the protein phosphorylation changes in wheat challenged by Pst. A total of 1537 and 2470 differentially accumulated phosphoproteins (DAPs) were identified from four early infection stage (6, 12, 18 and 24 h post-inoculation) in incompatible and compatible wheat-Pst interactions respectively. KEGG analysis revealed that Oxidative Phosphorylation, Phosphatidylinositol Signaling, and MAPK signaling processes are distinctively enriched in incompatible interaction, while Biosynthesis of secondary metabolites and RNA degradation process were significantly enriched in compatible interactions. In particular, abundant changes in phosphorylation levels of chloroplast proteins were identified, suggesting the regulatory role of photosynthesis in wheat-Pst interaction, which is further emphasized by protein-protein interaction (PPI) network analysis. Motif-x analysis identified [xxxxSPxxxx] motif, likely phosphorylation sites for defensive response-related kinases, and a new [xxxxSSxxxx] motif significantly enriched in incompatible interaction. The results shed light on the early phosphorylation events contributing to wheat resistance against Pst. Moreover, our study demonstrated that the phosphorylation levels of Nucleoside diphosphate kinase TaNAPK1 are upregulated at 12 hpi with CYR23 and at 24 hpi with CYR31. Transient silencing of TaNAPK1 was able to attenuate wheat resistance to CYR23 and CYR31. Our study provides new insights into the mechanisms underlying Pst-wheat interactions and may provide database to find potential targets for the development of new resistant varieties.

SUMMARY: Plant fungal parasites manipulate host metabolism to support their own survival. Among the many central metabolic pathways altered during infection, the glyoxylate cycle is frequently upregulated in both fungi and their host plants. Here, we examined the response of the glyoxylate cycle in bread wheat (Triticum aestivum) to infection by the obligate biotrophic fungal pathogen Puccinia striiformis f. sp. tritici (Pst). Gene expression analysis revealed that wheat genes encoding the two unique enzymes of the glyoxylate cycle, isocitrate lyase (TaICL) and malate synthase, diverged in their expression between susceptible and resistant Pst interactions. Focusing on TaICL, we determined that the TaICL B homoeolog is specifically upregulated during early stages of a successful Pst infection. Furthermore, disruption of the B homoeolog alone was sufficient to significantly perturb Pst disease progression. Indeed, Pst infection of the TaICL‐B disruption mutant (TaICL‐BY400*) was inhibited early during initial penetration, with the TaICL‐BY400* line also accumulating high levels of malic acid, citric acid, and aconitic acid. Exogenous application of malic acid or aconitic acid also suppressed Pst infection, with trans‐aconitic acid treatment having the most pronounced effect by decreasing fungal biomass 15‐fold. Thus, enhanced TaICL‐B expression during Pst infection may lower accumulation of malic acid and aconitic acid to promote Pst proliferation. As exogenous application of aconitic acid and malic acid has previously been shown to inhibit other critical pests and pathogens, we propose TaICL as a potential target for disruption in resistance breeding that could have wide‐reaching protective benefits for wheat and beyond. Significance Statement: Isocitrate lyase (ICL) is a unique enzyme of the glyoxylate cycle that frequently accumulates in fungi and their host plants. We uncovered a critical role for wheat ICL in supporting Puccinia striiformis f. sp. tritici (Pst) infection. Disruption of ICL function in wheat prevented Pst disease progression, likely due to the accumulation of glyoxylate cycle intermediates that can suppress Pst infection. ICL thus represents a new potential target for disruption in resistance breeding. [ABSTRACT FROM AUTHOR]

Cultivar resistance is a major asset for the management of crop diseases and can play an important role in agroecological transition. However, the wide deployment of a reduced number of resistance genes can lead to a rapid adaptation of pathogen populations and to a loss of resistance efficiency. The objective of this study was to characterize and discuss different trajectories of adult plant ratings for resistance to yellow rust in French wheat cultivars between 1963 and 2018. Among 719 cultivars assessed for at least 2 years, 590 cultivars showed no variation in their resistance scores, despite a mean of 4.3 years and up to 33 years of assessment. A set of descriptive variables was computed in order to compare the evolution of resistance score of 129 cultivars that experienced resistance variation. We applied a principal component analysis and a hierarchical clustering on principal components to this subdataset to constitute clusters corresponding to different cultivar profiles. Clusters C1 and C2 had small resistance variations (1–2 points on a 1–9 scale); Cluster C3 had long assessment durations and several small drops in resistance score and could be associated with quantitative resistance erosion; Cluster C4 included major drops in resistance score (4–5 points), often associated with known breakdowns of major resistance genes. Cases of limited drops in resistance score as a known resistance gene was broken down suggest the presence of efficient adult plant resistance. We discuss the use of information extracted from this dataset and methods to further explore sources of resistance to yellow rust present in French cultivars. [ABSTRACT FROM AUTHOR]

Actin filaments and their associated actin-binding proteins play key roles in plant innate immune signaling. CAP1, or cyclase-associated protein 1, is an important regulatory factor of the actin cytoskeleton-associated signaling network and was hypothesized here to be involved in resistance against wheat stripe rust because TaCAPl expression was upregulated in response to Puccinia striiformis f. sp. tritici (Pst). Downregulation of TaCAPl expression led to decreased resistance against P.vt, in contrast to increased resistance upon TaCAPl overexpressing, as demonstrated by the changes of phenotypes and hyphal growth. We found increased expression of pathogenesis-responsive or relative related genes and disease grade changed in 'TaCAPl overexpressing plants. Our results also showed TaCAP 1 -regulated host resistance to Pst by inducing the production and accumulation of reactive oxygen species and mediating the salicylic acid signaling pathway. Additionally, TaCAPl interacted with chlorophyll a/b- bindtng proteins TaLHCBU and TaLHCBI.4, also known as the lightharvesting chlorophyll-protein complex II subunit B. which belong to the light-harvesting complex II protein family. Silencing of two TaLHCBl genes showed higher susceptibility to Pst, which reduced wheat resistance against Pst. Therefore, the data presented herein further illuminate our understanding that TaCAPl interacts with TaLHCBls and functions as a positive regulator of wheat resistance against stripe rust. [ABSTRACT FROM AUTHOR]

Protein phosphorylation plays an important role in immune signaling transduction in plant resistance to pathogens. Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), severely devastates wheat production. Nonetheless, the molecular mechanism of wheat resistance to stripe rust remains limited. In this study, quantitative phosphoproteomics was employed to investigate the protein phosphorylation changes in wheat challenged by Pst. A total of 1537 and 2470 differentially accumulated phosphoproteins (DAPs) were identified from four early infection stage (6, 12, 18 and 24 h post-inoculation) in incompatible and compatible wheat-Pst interactions respectively. KEGG analysis revealed that Oxidative Phosphorylation, Phosphatidylinositol Signaling, and MAPK signaling processes are distinctively enriched in incompatible interaction, while Biosynthesis of secondary metabolites and RNA degradation process were significantly enriched in compatible interactions. In particular, abundant changes in phosphorylation levels of chloroplast proteins were identified, suggesting the regulatory role of photosynthesis in wheat-Pst interaction, which is further emphasized by protein-protein interaction (PPI) network analysis. Motif-x analysis identified [xxxxSPxxxx] motif, likely phosphorylation sites for defensive response-related kinases, and a new [xxxxSSxxxx] motif significantly enriched in incompatible interaction. The results shed light on the early phosphorylation events contributing to wheat resistance against Pst. Moreover, our study demonstrated that the phosphorylation levels of Nucleoside diphosphate kinase TaNAPK1 are upregulated at 12 hpi with CYR23 and at 24 hpi with CYR31. Transient silencing of TaNAPK1 was able to attenuate wheat resistance to CYR23 and CYR31. Our study provides new insights into the mechanisms underlying Pst-wheat interactions and may provide database to find potential targets for the development of new resistant varieties. [ABSTRACT FROM AUTHOR]

Abstract Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is a common airborne wheat disease. The frequent occurrence at a large scale in China has caused significant yield losses and poses a considerable threat to food security. To effectively manage and forecast the disease, a comprehensive understanding of the long-distance migration patterns of Pst is essential. Shaanxi province, situated in close proximity to the northwestern epidemic areas in China, plays a crucial role as a key overwintering region for Pst. However, it remains uncertain whether Pst, after winter reproduction in Shaanxi province, can extend its spread to the primary wheat regions in the North China Plain. In this study, during February and June 2022, a total of 302 Pst samples were collected from Shaanxi province and the North China Plain. Thirteen pairs of simple sequence repeat (SSR) markers were adopted to analyze the population genetic structure. It was observed that both genetic and genotypic diversities exhibited a discernible decline from the Shaanxi to the North China Plain. Moreover, Shaanxi displayed a close genetic relationship with Henan and Shandong, whereas Henan exhibited the most substantial population exchange with Shaanxi. Further analysis revealed that Shaanxi served as the primary inoculum of Pst in the investigated region, and the spread of Pst to Henan and Shandong originated from Shaanxi. As a result, the epidemics in Shandong further led to the prevailing of the disease in Hebei. Our study enhances the understanding of the epidemiological patterns of wheat stripe rust in the springtime prevalent regions of China, and it provides insights for future disease management.

Puccinia striiformis f. sp. tritici (Pst) is adept at overcoming resistance in wheat cultivars, through variations in virulence in the western provinces of China. To apply disease management strategies, it is essential to understand the temporal and spatial dynamics of Pst populations. This study aimed to evaluate the virulence and molecular diversity of 84 old Pst isolates, in comparison to 59 newer ones. By using 19 Chinese wheat differentials, we identified 98 pathotypes, showing virulence complexity ranging from 0 to 16. Associations between 23 Yr gene pairs showed linkage disequilibrium and have the potential for gene pyramiding. The new Pst isolates had a higher number of polymorphic alleles (1.97), while the older isolates had a slightly higher number of effective alleles, Shannon's information, and diversity. The Gansu Pst population had the highest diversity (uh = 0.35), while the Guizhou population was the least diverse. Analysis of molecular variance revealed that 94% of the observed variation occurred within Pst populations across the four provinces, while 6% was attributed to differences among populations. Overall, Pst populations displayed a higher pathotypic diversity of H > 2.5 and a genotypic diversity of 96%. This underscores the need to develop gene-pyramided cultivars to enhance the durability of resistance. [ABSTRACT FROM AUTHOR]

Wheat stripe/yellow rust (WYR), caused by Puccinia striiformis f. sp. tritici (Pst), is a major constraint in global wheat production. A set of 766 hexaploid synthetic wheat lines, including primary crosses of Triticum turgidum x Aegilops tauschii and their derivatives, were screened in artificially rust inoculated field nurseries for three seasons. From this set, a core set of 94 non-lodging lines with unique pedigrees and resistance to Pst that was consistent across years was established. The core set was tested for adult plant field response under field conditions for three seasons in Australia and at least one crop season in Ethiopia, India, Kenya, Nepal and Pakistan. It was also challenged with an array of well-defined Pst pathotypes at seedling growth stages in the greenhouse, and genotyped with molecular markers linked to the adult plant resistance (APR) genes Yr18, Yr36 and Yr46. Combined analysis of field rust responses, multi-pathotype seedling phenotyping and marker genotyping resolved seven classes of Pst resistance: uncatalogued (new) APR (UAPR, 11%), uncatalogued seedling resistance (USR, 46%), known seedling resistance (KSR, 5%), KSR + USR (2%), Yr18 + UAPR (4%), Yr18 + USR (29%) and Yr18 + KSR (3%). A majority of the lines carrying UAPR and USR either singly or in combination showed high levels of field resistance across all field sites and years of testing, demonstrating that these lines represent a valuable resource for breeding wheat for resistance to Pst. [ABSTRACT FROM AUTHOR]

N6-methyladenosine (m6A) is a prevalent internal modification in eukaryotic mRNA, tRNA, miRNA, and long non-coding RNA. It is also known for its role in plant responses to biotic and abiotic stresses. However, a comprehensive m6A transcriptome-wide map for Puccinia striiformis f. sp. tritici (Pst) infections in wheat (Triticum aestivum) is currently unavailable. Our study is the first to profile m6A modifications in wheat infected with a virulent Pst race. Analysis of RNA-seq and MeRIP-seq data revealed that the majority of differentially expressed genes are up-regulated and hyper-methylated. Some of these genes are enriched in the plant–pathogen interaction pathway. Notably, genes related to photosynthesis showed significant down-regulation and hypo-methylation, suggesting a potential mechanism facilitating successful Pst invasion by impairing photosynthetic function. The crucial genes, epitomizing the core molecular constituents that fortify plants against pathogenic assaults, were detected with varying expression and methylation levels, together with a newly identified methylation motif. Additionally, m6A regulator genes were also influenced by m6A modification, and their expression patterns varied at different time points of post-inoculation, with lower expression at early stages of infection. This study provides insights into the role of m6A modification regulation in wheat's response to Pst infection, establishing a foundation for understanding the potential function of m6A RNA methylation in plant resistance or susceptibility to pathogens. [ABSTRACT FROM AUTHOR]

Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is a common airborne wheat disease. The frequent occurrence at a large scale in China has caused significant yield losses and poses a considerable threat to food security. To effectively manage and forecast the disease, a comprehensive understanding of the long-distance migration patterns of Pst is essential. Shaanxi province, situated in close proximity to the northwestern epidemic areas in China, plays a crucial role as a key overwintering region for Pst. However, it remains uncertain whether Pst, after winter reproduction in Shaanxi province, can extend its spread to the primary wheat regions in the North China Plain. In this study, during February and June 2022, a total of 302 Pst samples were collected from Shaanxi province and the North China Plain. Thirteen pairs of simple sequence repeat (SSR) markers were adopted to analyze the population genetic structure. It was observed that both genetic and genotypic diversities exhibited a discernible decline from the Shaanxi to the North China Plain. Moreover, Shaanxi displayed a close genetic relationship with Henan and Shandong, whereas Henan exhibited the most substantial population exchange with Shaanxi. Further analysis revealed that Shaanxi served as the primary inoculum of Pst in the investigated region, and the spread of Pst to Henan and Shandong originated from Shaanxi. As a result, the epidemics in Shandong further led to the prevailing of the disease in Hebei. Our study enhances the understanding of the epidemiological patterns of wheat stripe rust in the springtime prevalent regions of China, and it provides insights for future disease management. [ABSTRACT FROM AUTHOR]

Abstract Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is a devastating disease that seriously threatens the production of crops worldwide. Triadimefon is the widely-used fungicide for controlling the disease in China; however, as the fungicide targets a single site (position 401 in the 134th codon of the Cyp51 gene), the extensive application imposes a strong selection pressure on the pathogens, which may potentially lose the effect over time. In this study, 176 Pst field isolates sampled from different regions of Xinjiang were determined for their sensitivity to triadimefon because it is the few frequent Pst outbreak and representative area in China. The results showed that the Pst isolates collected from Yili, Xinjiang, exhibited a strong resistance to triadimefon with an average EC50 of 0.263 µg/mL, despite the rest of the isolates maintaining high sensitivity to triadimefon. The triadimefon-resistant and triadimefon-sensitive isolates did not display significant differences in sporulation, but the triadimefon-resistant isolates exhibited weaker adaptive traits in their latent period and urediniospore germination rate than the triadimefon-sensitive isolates. No cross-resistance was found for the other two fungicides, flubeneteram or pyraclostrobin; however, cross-resistance for the demethylation inhibitor (DMI) fungicides, tebuconazole and hexaconazole, was found. Genome sequencing revealed that the Tyrosine (Y) at 134 residue was mutated to Phenylalanine (F) in the Xinjiang isolates. Our study revealed that a natural mutation in Pst led to the efficacy loss of triadimefon to control the disease.

Abstract Background The population structure of crop pathogens such as Puccinia striiformis f. sp. tritici (Pst), the cause of wheat stripe rust, is of interest to researchers looking to understand these pathogens on a molecular level as well as those with an applied focus such as disease epidemiology. Cereal rusts can reproduce sexually or asexually, and the emergence of novel lineages has the potential to cause serious epidemics such as the one caused by the ‘Warrior’ lineage in Europe. In a global context, Pst lineages in Canada were not well-characterized and the origin of foreign incursions was not known. Additionally, while some Pst mating type genes have been identified in published genomes, there has been no rigorous assessment of mating type diversity and distribution across the species. Results We used a whole-genome/transcriptome sequencing approach for the Canadian Pst population to identify lineages in their global context and evidence tracing foreign incursions. More importantly: for the first time ever, we identified nine alleles of the homeodomain mating type locus in the worldwide Pst population and show that previously identified lineages exhibit a single pair of these alleles. Consistently with the literature, we find only two pheromone receptor mating type alleles. We show that the recent population shift from the ‘PstS1’ lineage to the ‘PstS1-related’ lineage is also associated with the introduction of a novel mating type allele (Pst-b3-HD) to the Canadian population. We also show evidence for high levels of mating type diversity in samples associated with the Himalayan center of diversity for Pst, including a single Canadian race previously identified as ‘PstPr’ (probable recombinant) which we identify as a foreign incursion, most closely related to isolates sampled from China circa 2015. Conclusions These data describe a recent shift in the population of Canadian Pst field isolates and characterize homeodomain-locus mating type alleles in the global Pst population which can now be utilized in testing several research questions and hypotheses around sexuality and hybridization in rust fungi.

BackgroundStripe rust, caused by the fungus Puccinia striiformis f.sp. tritici (Pst), poses a significant threat to global wheat production.ObjectivesThis study aims to analyze the distribution of stripe rust resistance genes, characterize resistance phenotypes at the seedling stage of 137 spring and 149 winter wheat varieties in Xinjiang, China, and discern differences in resistance between spring and winter wheat varieties.DesignWe used various Pst races (CYR23, CYR29, CYR31, CYR32, CYR33, CYR34) to characterize seedling resistance of spring and winter wheat varieties and to correlate resistance to the presence of wheat resistance genes (Yr5, Yr9, Yr10, Yr15, Yr17, Yr18, Yr26, Yr41, Yr80, Yr81) using molecular markers.ResultsAmong spring wheat varieties, 62, 60, 42, 26, 51, and 24 varieties exhibited resistance to CYR23, CYR29, CYR31, CYR32, CYR33, and CYR34, respectively, with four varieties resistant to all varieties. Among winter wheat varieties, 66, 32, 69, 26, 83, 40 varieties demonstrated resistance to CYR23, CYR29, CYR31, CYR32, CYR33, and CYR34, respectively, with four varieties resistant to all varieties. Molecular testing revealed that, in spring wheat, 2, 17, 21, 61, 10, 0, 10, 79, and 32 varieties carried Yr9, Yr10, Yr15, Yr17, Yr18, Yr26, Yr41, Yr80, and Yr81 genes, respectively. In winter wheat, 40, 20, 7, 143, 15, 1, 6, 38, and 54 varieties carried Yr9, Yr10, Yr15, Yr17, Yr18, Yr26, Yr41, Yr80, and Yr81 genes, respectively. Notably, winter wheat exhibited a significantly higher resistance frequency than spring wheat, particularly in the incidence of Yr9, Yr10, Yr17, Yr18, and multi-gene combinations.ConclusionIn summary, this study provides information on seedling stage resistance to stripe rust 286 Xinjiang wheat varieties, elucidates the distribution of resistance genes in this population, and offers a mechanistic basis for breeding durable resistance in wheat. varieties from Xinjiang.

Stripe rust, a fungal disease caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most destructive diseases affecting wheat production areas worldwide. In recent years in China, wheat stripe rust has caused huge yield losses throughout the vast Huang-Huai-Hai region, including the eastern coast regions, especially Shandong province. The aim of the present study was to explore the population structure and potential inoculum sources of the pathogen in this region. A total of 234 Pst isolates in 2021 were collected and isolated from seven provinces and identified for virulence phenotypes using 19 Chinese differentials and for genotypes using 17 single-nucleotide polymorphism-based Kompetitive allele-specific PCR markers. The virulence phenotype tests identified predominant races CYR34 (18.0%) and CYR32 (16.0%) in Shandong, which were similar to the results in Henan province, also with the predominant races CYR34 (21.9%) and CYR32 (18.8%). Based on the virulence data of phenolyping, the Pst populations in Shandong, Hubei, and Henan were similar. The genotypic analysis revealed remarkable gene flows among the Shandong, Hubei, Henan, Yunnan, and Guizhou populations, showing a migration of Pst from the southwestern oversummering regions to Shandong through the winter spore production regions. Genetic structure analysis also indicated an additional migration route from the northwestern oversummering regions through winter spore production regions to Shandong. The results are useful for understanding stripe rust epidemiology in the eastern coast region and improving control of the disease throughout the country. [ABSTRACT FROM AUTHOR]

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most important diseases threatening wheat production both in Turkey and worldwide. However, the underlying genetic dynamics of Pst populations are not fully known in Turkey. To determine the population genetic structure and migration network among regional Pst populations, a total of 140 Pst isolates collected from six geographical regions of Turkey from 2018 to 2020 were sampled and genotyped using 21 simple sequence repeat loci. A total of 70 multilocus genotypes were identified and classified into the three major genetic groups by Bayesian assignment. The highest genotypic diversity was detected in Southeastern Anatolia, showing its critical role as one of the source populations to trigger possible stripe rust epidemics. Analysis of molecular variance revealed the highest variation (90.25%) within isolates. The migration network generated by the number of effective migrants showed that the highest migration (1.0) was determined between Southeastern Anatolia and Central Anatolia, and considerable levels of migration (>0.2) were determined among the other regions, except for the Black Sea. Linkage equilibrium (P > 0.05) was detected for many geographical regions, except for Marmara (P = 0.00) and the Mediterranean (P = 0.03), suggesting that reproduction of Pst populations is most likely sexual or mixed (sexual and clonal). To sum up, this is the first study on the genetic relationships and population genetic structure of the Pst population in Turkey, and these findings may provide critical information to develop management strategies for wheat stripe rust. [ABSTRACT FROM AUTHOR]

Puccinia striiformis f. sp. tritici is an obligate biotrophic fungus that causes destructive stripe rust disease in wheat. During infection, Pst secretes virulence effectors via a specific infection structure—the haustorium—inside host cells to disturb host immunity and promote fungal colonization and expansion. Hence, the identification and functional analyses of Pst effectors are of great significance in deciphering the Pst pathogenicity mechanism. Here, we identified one candidate Pst effector Pst_9302 that could suppress Bax-triggered cell death in Nicotiana benthamiana. qRT-PCR analyses showed that the transcript levels of Pst_9302 were highly increased during the early infection stages of Pst. The transient expression of Pst_9302 in wheat via the type-three secretion system (T3SS) significantly inhibited the callose deposition induced by Pseudomonas syringae EtHAn. During wheat–Pst interaction, Pst_9302 overexpression suppressed reactive oxygen species (ROS) accumulation and cell death caused by the avirulent Pst race CYR23. The host-induced gene silencing (HIGS) of Pst_9302 resulted in decreased Pst pathogenicity with reduced infection area. The results suggest that Pst_9302 plays a virulence role in suppressing plant immunity and promoting Pst pathogenicity. Moreover, wheat voltage-dependent anion channel 1 protein (TaVDAC1) was identified as candidate Pst_9302-interacting proteins by yeast two-hybrid (Y2H) screening. Pull-down assays using the His-Pst_9302 and GST-TaVDAC1 protein verified their interactions. These results suggest that Pst_9302 may modulate wheat TaVDAC1 to regulate plant immunity. [ABSTRACT FROM AUTHOR]

Wheat cultivar Xiaoyan 6 (XY6) has high‐temperature seedling‐plant (HTSP) resistance to Puccinia striiformis f. sp. tritici (Pst). However, the molecular mechanism of Pst effectors involved in HTSP resistance remains unclear. In this study, we determined the interaction between two Pst effectors, PstCEP1 and PSTG_11208, through yeast two‐hybrid (Y2H), bimolecular fluorescence complementation (BiFC), and pull‐down assays. Transient overexpression of PSTG_11208 enhanced HTSP resistance in different temperature treatments. The interaction between PstCEP1 and PSTG_11208 inhibited the resistance enhancement by PSTG_11208. Furthermore, the wheat apoplastic thaumatin‐like protein 1 (TaTLP1) appeared to recognize Pst invasion by interacting with PSTG_11208 and initiate the downstream defence response by the pathogenesis‐related protein TaPR1. Silencing of TaTLP1 and TaPR1 separately or simultaneously reduced HTSP resistance to Pst in XY6. Moreover, we found that PstCEP1 targeted wheat ferredoxin 1 (TaFd1), a homologous protein of rice OsFd1. Silencing of TaFd1 affected the stability of photosynthesis in wheat plants, resulting in chlorosis on the leaves and reducing HTSP resistance. Our findings revealed the synergistic mechanism of effector proteins in the process of pathogen infection. [ABSTRACT FROM AUTHOR]

Plants have the ability to recognize the essential chitin molecule present in the fungal cell wall, which stimulates the immune response. Phytopathogenic fungi have developed various strategies to inhibit the chitin‐triggered immune response. Here, we identified a chitin deacetylase of Puccinia striiformis f. sp. tritici (Pst), known as PsCDA2, that was induced during the initial invasion of wheat and acted as an inhibitor of plant cell death. Knockdown of PsCDA2 in wheat enhanced its resistance against Pst, highlighting the significance of PsCDA2 in the host–pathogen interaction. Moreover, PsCDA2 can protect Pst urediniospores from being damaged by host chitinase in vitro. PsCDA2 also suppressed the basal chitin‐induced plant immune response, including the accumulation of callose and the expression of defence genes. Overall, our results demonstrate that Pst secretes PsCDA2 as a chitin deacetylase involved in establishing infection and modifying the acetyl group to prevent the breakdown of chitin in the cell wall by host endogenous chitinases. Our research unveils a mechanism by which the fungus suppresses plant immunity, further contributing to the understanding of wheat stripe rust control. This information could have significant implications for the development of suitable strategies for protecting crops against the devastating effects of this disease. [ABSTRACT FROM AUTHOR]

Abstract The devastating wheat stripe (yellow) rust pathogen, Puccinia striiformis f. sp. tritici (Pst), is a macrocyclic and heteroecious 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.

Abstract Background Puccinia striiformis f. sp. tritici (Pst) is an economically devasting disease that is prominent in cereal crops such as wheat (Triticum aestivum). The fungal pathogen can cause approximately 30–70% losses in crop productivity and yields. Pst has become difficult to manage due to its ease of transmission through wind dispersal over long distances, and intercontinental dispersal has been previously reported. The ease of transmission has resulted in further destruction because of new and more virulent strains infecting crops previously resistant to a different strain. Results In this study, a liquid chromatography-mass spectrometry-based untargeted metabolomics approach, in combination with multivariate data analytical tools, was used to elucidate the mechanistic nature of the defence systems of a Pst-resistant and a susceptible wheat cultivar infected with P. striiformis. We also investigated the time-dependant metabolic reconfiguration of infected plants over a four-week period. The untargeted metabolomic analysis revealed a time-course metabolic reprogramming involving phenylpropanoids (majority flavonoids), amino acids, lipids, benzoic acids, TCA cycle intermediates and benzoxazinoids responding to Pst infection. Interestingly, the results do not show a linear course for the decrease and increase (up-/down-regulation) of said classes of metabolites, but rather the up- or down-regulation of specific metabolites in response to the pathogen infection. The resistant Koonap cultivar had an abundance of phenolic compounds such as rutin, isoorintin-7-O-glucoside and luteolin-6-C-hexoside-O-hexoside. These compounds showed a decrease over time in control Koonap plants compared to an increase in Pst-infected plants. These metabolites were down-regulated in the susceptible Gariep cultivar, which could serve as biomarkers for plant responses to biotic stress and resistance against Pst. Conclusions Overall, an LC-MS-based metabolomics approach allowed for the metabolic profiling and analysis of the impact of plant-pathogen interactions on the overall plant metabolome and provided a real-time snapshot of the differential significant metabolic perturbations occurring in wheat plants responding to the Pst pathogen. The Pst-resistant Koonap cultivar showed a rapid accumulation of defence metabolites in response to pathogen infection compared to the susceptible Gariep cultivar. These findings provide insight into the mechanistic biochemical nature of plant-microbe interactions and the prospects of metabolic engineering for improved plant tolerance and resistance to biotic stresses.

Background: The population structure of crop pathogens such as Puccinia striiformis f. sp. tritici (Pst), the cause of wheat stripe rust, is of interest to researchers looking to understand these pathogens on a molecular level as well as those with an applied focus such as disease epidemiology. Cereal rusts can reproduce sexually or asexually, and the emergence of novel lineages has the potential to cause serious epidemics such as the one caused by the 'Warrior' lineage in Europe. In a global context, Pst lineages in Canada were not well-characterized and the origin of foreign incursions was not known. Additionally, while some Pst mating type genes have been identified in published genomes, there has been no rigorous assessment of mating type diversity and distribution across the species. Results: We used a whole-genome/transcriptome sequencing approach for the Canadian Pst population to identify lineages in their global context and evidence tracing foreign incursions. More importantly: for the first time ever, we identified nine alleles of the homeodomain mating type locus in the worldwide Pst population and show that previously identified lineages exhibit a single pair of these alleles. Consistently with the literature, we find only two pheromone receptor mating type alleles. We show that the recent population shift from the 'PstS1' lineage to the 'PstS1-related' lineage is also associated with the introduction of a novel mating type allele (Pst-b3-HD) to the Canadian population. We also show evidence for high levels of mating type diversity in samples associated with the Himalayan center of diversity for Pst, including a single Canadian race previously identified as 'PstPr' (probable recombinant) which we identify as a foreign incursion, most closely related to isolates sampled from China circa 2015. Conclusions: These data describe a recent shift in the population of Canadian Pst field isolates and characterize homeodomain-locus mating type alleles in the global Pst population which can now be utilized in testing several research questions and hypotheses around sexuality and hybridization in rust fungi. [ABSTRACT FROM AUTHOR]

Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is a devastating disease that seriously threatens the production of crops worldwide. Triadimefon is the widely-used fungicide for controlling the disease in China; however, as the fungicide targets a single site (position 401 in the 134th codon of the Cyp51 gene), the extensive application imposes a strong selection pressure on the pathogens, which may potentially lose the effect over time. In this study, 176 Pst field isolates sampled from different regions of Xinjiang were determined for their sensitivity to triadimefon because it is the few frequent Pst outbreak and representative area in China. The results showed that the Pst isolates collected from Yili, Xinjiang, exhibited a strong resistance to triadimefon with an average EC50 of 0.263 µg/mL, despite the rest of the isolates maintaining high sensitivity to triadimefon. The triadimefon-resistant and triadimefon-sensitive isolates did not display significant differences in sporulation, but the triadimefon-resistant isolates exhibited weaker adaptive traits in their latent period and urediniospore germination rate than the triadimefon-sensitive isolates. No cross-resistance was found for the other two fungicides, flubeneteram or pyraclostrobin; however, cross-resistance for the demethylation inhibitor (DMI) fungicides, tebuconazole and hexaconazole, was found. Genome sequencing revealed that the Tyrosine (Y) at 134 residue was mutated to Phenylalanine (F) in the Xinjiang isolates. Our study revealed that a natural mutation in Pst led to the efficacy loss of triadimefon to control the disease. [ABSTRACT FROM AUTHOR]

Puccinia striiformis Westend. f. sp. tritici Eriksson (Pst), the causal agent of stripe rust, is known as an important and destructive pathogen that causes critical wheat losses in many parts of the world. Employing effective resistant genotypes is a safe and operative strategy to combat the disease. Iran is located in the Fertile Crescent, the co-epicentre of wheat and its biotic stresses. Iranian wheat landraces may carry important sources of resistance against rust diseases. Adult plant reactions of 467 Iranian wheat landraces to stripe rust were studied in two cropping seasons in Fars province. One hundred and six landraces showed acceptable levels of resistance and were selected for further seedling and molecular studies based on their lower infection type, coefficient of infection (CI) and average coefficient of infection (ACI). The presence of Yr4, Yr10, Yr24 and Yr32 resistance genes were postulated using 10 different Pst isolates including PstS10, PstS7, PstS3, PstS2+V27, PstS11, PstS8, PstS13, PstS6, PstS0 and Me2018 under greenhouse conditions. Field and greenhouse reactions of near-isogenic lines reconfirmed the presence of the studied Yr resistance genes in 20 genotypes. Moreover, Xcfb3530150, Xpsp3000, Xgwm11, and Xwmc198 SSR markers were employed to identify and validate the presence of the above corresponding genes. The presence of Yr4, Yr10, Yr24 and Yr32 resistance genes in five (1.07%), 10 (2.14%), five (1.07%) and seven (1.5%) experimental landraces were confirmed, respectively. Six genotypes are harbouring more than one resistance gene. These effective resistance sources can be employed in national and international breeding programs. [ABSTRACT FROM AUTHOR]

Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is an important cereal fungal disease worldwide, including in the major wheat‐producing areas in China. In 2019, there was a widespread epidemic of the disease in the middle and lower reaches of the Yangtze River (MLRYR) area, including Zhejiang, Jiangsu, Anhui and Guangxi. However, in north‐western China, the postulated inoculum source of MLRYR, disease occurred mildly. Therefore, the origin of the Pst inoculum source for the MLRYR epidemic is still an open question. To address it, we collected 210 Pst uredinium samples from the Yangtze River basin and analysed their genetic structure with 13 pairs of simple‐sequence repeat (SSR) markers that we coupled with an upper airflow trajectory analysis. Our results suggest that the autumn inoculum sources of wheat stripe rust in MLRYR in 2019 probably came from south‐western over‐summering areas of Pst through long‐distance migration. We also found that Jingzhou and adjacent areas in Hubei Province function as an important bridge or stopover for inoculum sources. [ABSTRACT FROM AUTHOR]

The dynamic balance and distribution of sphingolipid metabolites modulate the level of programmed cell death and plant defence. However, current knowledge is still limited regarding the molecular mechanism underlying the relationship between sphingolipid metabolism and plant defence. In this study, we identified a wheat RNA‐binding protein 1 (TaRBP1) and TaRBP1 mRNA accumulation significantly decreased in wheat after infection by Puccinia striiformis f. sp. tritici (Pst). Knockdown of TaRBP1 via virus‐induced gene silencing conferred strong resistance to Pst by enhancing host plant reactive oxygen species (ROS) accumulation and cell death, indicating that TaRBP1 may act as a negative regulator in response to Pst. TaRBP1 formed a homopolymer and interacted with TaRBP1 C‐terminus in plants. Additionally, TaRBP1 physically interacted with TaGLTP, a sphingosine transfer protein. Knockdown of TaGLTP enhanced wheat resistance to the virulent Pst CYR31. Sphingolipid metabolites showed a significant accumulation in TaGLTP‐silenced wheat and TaRBP1‐silenced wheat, respectively. In the presence of the TaRBP1 protein, TaGLTP failed to be degraded in a 26S proteasome‐dependent manner in plants. Our results reveal a novel susceptible mechanism by which a plant fine‐tunes its defence responses by stabilizing TaGLTP accumulation to suppress ROS and sphingolipid accumulation during Pst infection. [ABSTRACT FROM AUTHOR]

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.

Abstract Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is a devastating disease threatening global wheat production. Biocontrol by beneficial microorganisms is considered an alternative to synthetic fungicide applications. This study aimed to investigate the mechanisms involved in the biocontrol of wheat stripe rust by streptomycetes. A streptomycete strain XF, isolated from the rhizospheric soil of peony, was identified as Streptomyces tauricus based on morphological characteristics and phylogenetic analysis. We determined the inhibitory effect of XF on Pst and biocontrol effect on the disease using XF fermentation filtrate (FL) and actinomycete cell suspension (AC). Results revealed that FL inhibited urediniospore germination by up to 99% and rendered a lethality rate of 61.47% against urediniospores. Additionally, crude extract of ethyl acetate phase of FL caused cytoplasm releases from urediniospores and the deformation of germ tubes. Furthermore, histochemical analyses revealed that treatments of plants with AC and FL increased reactive oxygen species, inhibited haustorium formation, and reduced the biomass of Pst in leaves. Electron microscopy showed that XF mycelium was able to colonize the leaf surface. Moreover, gene expression assays revealed that AC and FL treatments induced the expression of a number of pathogenesis-related genes in wheat leaves. Besides, in the greenhouse experiments, the control effects of AC and FL reached 65.48% and 68.25%, respectively. In the field, application of XF fermentation broth significantly reduced the disease indices of stripe rust by 53.83%. These findings suggest that XF is a potential biocontrol agent for managing wheat stripe rust disease.

The devastating wheat stripe (yellow) rust pathogen, Puccinia striiformis f. sp. tritici (Pst), is a macrocyclic and heteroecious 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. [ABSTRACT FROM AUTHOR]

Somatic embryogenesis receptor kinases (SERKs) belong to the leucine-rich repeat receptor-like kinase (LRR-RLK) subfamily, and many LRR- RLKs have been proven to play a key role in plant immune signal transmission. However, the functions of SERKs in resistance to stripe rust caused by Puccinia striiformis f. sp. tritici remains unknown. Here, we identified a gene, TaSERKl, from Xiaoyan 6, a wheat cultivar possessing high-temperature seedling-plant (HTSP) resistance to the fungal pathogen P. striiformis f. sp. tritici and expresses its resistance at the seedling stage. The expression level of TaSERKl was upregulated upon P. striiformis f. sp. tritici inoculation under relatively high temperatures. The transcriptional level of TaSERK 1 was significantly increased under exogenous salicylic acid and brassinosteroids treatments. The barley stripe mosaic virus-induced gene silencing assay indicated that TaSERKl positively regulated the HTSP resistance to stripe rust. The transient expression of TaSERKl in tobacco leaves confirmed its subcellular localization on the plasma membrane. Furthermore, TaSERKl interacted with and phosphorylated the chaperone protein TaDJA7, which belongs to the heat shock protein 40 subfamily. Silencing TaDJA7 compromised the HTSP resistance to stripe rust. The results indicated that when the membrane immune receptor TaSERKl perceives the P. striiformis f. sp. tritici infection under relatively high temperatures, it transmits the signal to TaDJA7 to activate HTSP resistance to the pathogen. [ABSTRACT FROM AUTHOR]

Background: Puccinia striiformis f. sp. tritici (Pst) is an economically devasting disease that is prominent in cereal crops such as wheat (Triticum aestivum). The fungal pathogen can cause approximately 30–70% losses in crop productivity and yields. Pst has become difficult to manage due to its ease of transmission through wind dispersal over long distances, and intercontinental dispersal has been previously reported. The ease of transmission has resulted in further destruction because of new and more virulent strains infecting crops previously resistant to a different strain. Results: In this study, a liquid chromatography-mass spectrometry-based untargeted metabolomics approach, in combination with multivariate data analytical tools, was used to elucidate the mechanistic nature of the defence systems of a Pst-resistant and a susceptible wheat cultivar infected with P. striiformis. We also investigated the time-dependant metabolic reconfiguration of infected plants over a four-week period. The untargeted metabolomic analysis revealed a time-course metabolic reprogramming involving phenylpropanoids (majority flavonoids), amino acids, lipids, benzoic acids, TCA cycle intermediates and benzoxazinoids responding to Pst infection. Interestingly, the results do not show a linear course for the decrease and increase (up-/down-regulation) of said classes of metabolites, but rather the up- or down-regulation of specific metabolites in response to the pathogen infection. The resistant Koonap cultivar had an abundance of phenolic compounds such as rutin, isoorintin-7-O-glucoside and luteolin-6-C-hexoside-O-hexoside. These compounds showed a decrease over time in control Koonap plants compared to an increase in Pst-infected plants. These metabolites were down-regulated in the susceptible Gariep cultivar, which could serve as biomarkers for plant responses to biotic stress and resistance against Pst. Conclusions: Overall, an LC-MS-based metabolomics approach allowed for the metabolic profiling and analysis of the impact of plant-pathogen interactions on the overall plant metabolome and provided a real-time snapshot of the differential significant metabolic perturbations occurring in wheat plants responding to the Pst pathogen. The Pst-resistant Koonap cultivar showed a rapid accumulation of defence metabolites in response to pathogen infection compared to the susceptible Gariep cultivar. These findings provide insight into the mechanistic biochemical nature of plant-microbe interactions and the prospects of metabolic engineering for improved plant tolerance and resistance to biotic stresses. [ABSTRACT FROM AUTHOR]

N6-methyladenosine (m6A) is a prevalent internal modification in eukaryotic mRNA, tRNA, miRNA, and long non-coding RNA. It is also known for its role in plant responses to biotic and abiotic stresses. However, a comprehensive m6A transcriptome-wide map for Puccinia striiformis f. sp. tritici (Pst) infections in wheat (Triticum aestivum) is currently unavailable. Our study is the first to profile m6A modifications in wheat infected with a virulent Pst race. Analysis of RNA-seq and MeRIP-seq data revealed that the majority of differentially expressed genes are up-regulated and hyper-methylated. Some of these genes are enriched in the plant–pathogen interaction pathway. Notably, genes related to photosynthesis showed significant down-regulation and hypo-methylation, suggesting a potential mechanism facilitating successful Pst invasion by impairing photosynthetic function. The crucial genes, epitomizing the core molecular constituents that fortify plants against pathogenic assaults, were detected with varying expression and methylation levels, together with a newly identified methylation motif. Additionally, m6A regulator genes were also influenced by m6A modification, and their expression patterns varied at different time points of post-inoculation, with lower expression at early stages of infection. This study provides insights into the role of m6A modification regulation in wheat’s response to Pst infection, establishing a foundation for understanding the potential function of m6A RNA methylation in plant resistance or susceptibility to pathogens.

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 effective 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 underlying mechanisms remain elusive. Here, we show that WKS1 interacts with and phosphorylates PsbO, an extrinsic member of photosystem II (PSII), 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 PSII and reduces the binding affinity of PsbO with PSII. Presumably, phosphorylated PsbO proteins dissociate from the PSII complex and then undergo 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 photosynthesis and delay the growth of Pst pathogen before the induction of ROS.

Plant cell walls are composed of polysaccharides such as cellulose, hemicelluloses, and pectins, whose location and function differ depending on plant type. UDP‐Ara mutases (UAMs) have been reported to play important roles in plant development and response to various plant stresses (abiotic and biotic). However, little work has been reported on UAM in wheat. In this study, we dissected the role of the UAM family member, UAM3, during the interaction between wheat and the stripe rust fungus, Puccinia striiformis f. sp. tritici (Pst), and in response to treatment with salicylic acid (SA). RNA interference (RNAi)‐based stable silencing of TaUAM3 resulted in decreased resistance to Pst fungus. In addition, CRISPR‐mediated genome editing (GE) of TaUAM3 enhanced the susceptibility of wheat to Pst or compromised disease resistance accompanied by increased fungal growth and decreased H2O2 production in plant tissues. Moreover, the transcript levels of pathogenesis‐related (PR) genes and reactive oxygen species (ROS)‐generating genes were down‐regulated in both the RNAi‐silenced and CRISPR‐edited plants, while the ROS‐scavenging gene, TaCAT3, was up‐regulated. Therefore, TaUAM3 positively regulates the resistance of wheat to Pst. [ABSTRACT FROM AUTHOR]

Chitin is the main component of fungal cell walls, which can be recognized by pattern recognition receptors (PRRs) as pathogen-associated molecular patterns (PAMP). Chitinase in filamentous fungi has been reported to degrade immunogenic chitin oligomers, thereby preventing chitin-induced immune activation. In this study, we identified the chitinase families in 10 fungal genomes. A total of 131 chitinase genes were identified. Among the chitinase families, 16 chitinase genes from Puccinia striiformis f. sp. tritici (Pst) were identified, and the expression of PstChia1 was the highest during Pst infection. Further studies indicated that PstChia1 is highly induced during the early stages of the interaction of wheat and Pst and has chitinase enzyme activity. The silencing of PstChia1 revealed that PstChia1 limited the growth and reduced the virulence of Pst. The expression level of TaPR1 and TaPR2 was induced in PstChia1 knockdown plants, suggesting that PstChia1 is involved in regulating wheat resistance to Pst. Our data suggest that PstChia1 contributes to pathogenicity by interfering with plant immunity and regulating the growth of Pst. [ABSTRACT FROM AUTHOR]

Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is a devastating disease threatening global wheat production. Biocontrol by beneficial microorganisms is considered an alternative to synthetic fungicide applications. This study aimed to investigate the mechanisms involved in the biocontrol of wheat stripe rust by streptomycetes. A streptomycete strain XF, isolated from the rhizospheric soil of peony, was identified as Streptomyces tauricus based on morphological characteristics and phylogenetic analysis. We determined the inhibitory effect of XF on Pst and biocontrol effect on the disease using XF fermentation filtrate (FL) and actinomycete cell suspension (AC). Results revealed that FL inhibited urediniospore germination by up to 99% and rendered a lethality rate of 61.47% against urediniospores. Additionally, crude extract of ethyl acetate phase of FL caused cytoplasm releases from urediniospores and the deformation of germ tubes. Furthermore, histochemical analyses revealed that treatments of plants with AC and FL increased reactive oxygen species, inhibited haustorium formation, and reduced the biomass of Pst in leaves. Electron microscopy showed that XF mycelium was able to colonize the leaf surface. Moreover, gene expression assays revealed that AC and FL treatments induced the expression of a number of pathogenesis-related genes in wheat leaves. Besides, in the greenhouse experiments, the control effects of AC and FL reached 65.48% and 68.25%, respectively. In the field, application of XF fermentation broth significantly reduced the disease indices of stripe rust by 53.83%. These findings suggest that XF is a potential biocontrol agent for managing wheat stripe rust disease. [ABSTRACT FROM AUTHOR]

Stripe or yellow rust caused by Puccinia striiformis f. sp. tritici (Pst) is the most important disease of wheat causing significant yield losses. Growing resistant varieties is the most efficient and sustainable way to control this disease. The aim of this study was to investigate molecularly the presence or absence of the major resistance genes Yr5, Yr10 and Yr15 to stripe rust in 54 Turkish durum wheat (Triticum turgidum var. durum) varieties and 11 wild emmer (Triticum turgidum var. dicoccoides) genotypes. In addition, field trials were conducted during 2019–2020 under natural epidemic conditions in Antalya to determine phenotypic reactions of these genotypes against stripe rust. As a result of molecular analyses, none of the 54 durum wheat varieties had Yr5 resistance gene; however, the resistance genes Yr10 and Yr15 were determined in 12 and 17 varieties, respectively. Moreover, 7 of these varieties had both Yr10 and Yr15 genes. None of 11 wild emmer accessions had resistance genes examined. It was also determined that 28 varieties had resistant reaction to Pst race(s) under natural infection conditions whereas all wild emmer accessions were highly susceptible. This is the first study to identify major Yr-genes in Turkish durum wheat varieties and, therefore, these findings can be beneficial in wheat breeding programs to be conducted for resistance to stripe rust. [ABSTRACT FROM AUTHOR]

Yellow rust disease caused by Puccinia striiformis f. sp. tritici (Pst) is the most destructive disease of wheat and the most effective control method against the disease is the use of resistant plants. For this reason, the cultivars commonly grown should be tested against the current disease population or Pst race/races of high virulence. In this study, the infection of yellow rust on 54 durum wheat cultivars registered in Türkiye was evaluated under natural conditions. This study was carried out with two replicates on the campus of Akdeniz University during the 2017-2018 years. For the disease assessment, the modified Cobb scale was used and the infection of the coefficient was calculated according to the disease reaction determined. Based on the results of this study, it was found that most of the varieties were moderately susceptible and susceptible to the natural yellow rust infection in both years. Additionally, Kızıltan 91, Altın 40/98, Yılmaz 98, İmren, Çeşit 1252, and Kunduru 1149 varieties were resistant to the current disease population under field conditions. In further studies, it is necessary to determine the resistance gene or genes found in these cultivars by molecular methods. Additionally, it is important that new varieties developed in breeding programs were analyzed for Pst races identified in our country for the control of the disease.

Puccinia striiformis f. sp. tritici (Pst), the airborne fungal pathogen of wheat stripe rust, causes a decline in wheat quality and severe yield loss. Effective field management of wheat stripe rust heavily relies on timely and accurate monitoring of incoming fungal sources. Therefore, rapid and accurate detection of Pst is invaluable in disease control programs. In this study, three assays using recombinase polymerase amplification (RPA) combined with different visualization methods, including RPA followed by agarose gel electrophoresis, RPA lateral-flow dipstick (RPA-LFD) technology, and real-time RPA, were developed for rapidly and sensitively detecting Pst. The RPA and RPA-LFD assays were conducted at an isothermal temperature of 39 °C within 30 min. The real-time RPA assay required only a 20-min reaction at 39 °C. The specificities of the three assays were determined based on the lack of cross-reactivity with the other seven control wheat pathogens. The detection limits of RPA and real-time RPA were 105 fg/μL, and that of RPA-LFD was 104 fg/μL. Additionally, the three RPA assays detected Pst in field leaf samples. Among the 73 samples examined, 44 (60.3 %), 45 (61.6 %), and 60 (82.2 %) tested positive in the RPA, real-time RPA, and RPA-LFD assays, respectively. The result suggested that RPA-LFD was the most sensitive in detecting Pst from field samples. Giving the simple, rapid, and practical nature of RPA assays, this method can serve as a promising molecular diagnostic tools for accurate and rapid detection of Pst. [ABSTRACT FROM AUTHOR]

Puccinia striiformis f. sp. tritici is an obligate biotrophic fungus that causes destructive stripe rust disease in wheat. During infection, Pst secretes virulence effectors via a specific infection structure—the haustorium—inside host cells to disturb host immunity and promote fungal colonization and expansion. Hence, the identification and functional analyses of Pst effectors are of great significance in deciphering the Pst pathogenicity mechanism. Here, we identified one candidate Pst effector Pst_9302 that could suppress Bax-triggered cell death in Nicotiana benthamiana. qRT-PCR analyses showed that the transcript levels of Pst_9302 were highly increased during the early infection stages of Pst. The transient expression of Pst_9302 in wheat via the type-three secretion system (T3SS) significantly inhibited the callose deposition induced by Pseudomonas syringae EtHAn. During wheat–Pst interaction, Pst_9302 overexpression suppressed reactive oxygen species (ROS) accumulation and cell death caused by the avirulent Pst race CYR23. The host-induced gene silencing (HIGS) of Pst_9302 resulted in decreased Pst pathogenicity with reduced infection area. The results suggest that Pst_9302 plays a virulence role in suppressing plant immunity and promoting Pst pathogenicity. Moreover, wheat voltage-dependent anion channel 1 protein (TaVDAC1) was identified as candidate Pst_9302-interacting proteins by yeast two-hybrid (Y2H) screening. Pull-down assays using the His-Pst_9302 and GST-TaVDAC1 protein verified their interactions. These results suggest that Pst_9302 may modulate wheat TaVDAC1 to regulate plant immunity.

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 cM genetic interval on the chromosome arm 7BL 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.

Summary: Wheat stripe rust caused by the fungus Puccinia striiformis f. sp. tritici (Pst) is one of the most destructive wheat diseases resulting in significant losses to wheat production worldwide. The development of disease‐resistant varieties is the most economical and effective measure to control diseases. Altering the susceptibility genes that promote pathogen compatibility via CRISPR/Cas9‐mediated gene editing technology has become a new strategy for developing disease‐resistant wheat varieties. Calcineurin B‐like protein (CBL)‐interacting protein kinases (CIPKs) has been demonstrated to be involved in defence responses during plant‐pathogen interactions. However, whether wheat CIPK functions as susceptibility factor is still unclear. Here, we isolated a CIPK homoeologue gene TaCIPK14 from wheat. Knockdown of TaCIPK14 significantly increased wheat resistance to Pst, whereas overexpression of TaCIPK14 resulted in enhanced wheat susceptibility to Pst by decreasing different aspects of the defence response, including accumulation of ROS and expression of pathogenesis‐relative genes. We generated wheat Tacipk14 mutant plants by simultaneous modification of the three homoeologues of wheat TaCIPK14 via CRISPR/Cas9 technology. The Tacipk14 mutant lines expressed race‐nonspecific (RNS) broad‐spectrum resistance (BSR) to Pst. Moreover, no significant difference was found in agronomic yield traits between Tacipk14 mutant plants and Fielder control plants under greenhouse and field conditions. These results demonstrate that TaCIPK14 acts as an important susceptibility factor in wheat response to Pst, and knockout of TaCIPK14 represents a powerful strategy for generating new disease‐resistant wheat varieties with BSR to Pst. [ABSTRACT FROM AUTHOR]

Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is an extremely destructive wheat disease worldwide. Yunnan and Guizhou provinces are the main overwintering regions for Pst and inoculum sources for the disease in China. Surveillance of race dynamics of the Pst population is essential for managing the disease in local and other wheat-growing regions of China. However, Pst population dynamics in this region is not monitored yearly. In this study, a Pst population of 113 isolates from Yunnan and Guizhou in 2018 were phenotyped on the two wheat differential sets and analyzed by 12 simple sequence repeat (SSR) markers. As a result, 25 races were identified from the Pst population on Chinese differentials and predominant races was CYR32 with a frequency of 17.70%. None of the isolates was virulent to Yr5 and Yr15. Only a few isolates showed virulence to YrTr1 and differentials Zhong 4. The Kosman index (K) of the Pst population was 0.292 on the Chinese differentials, and 0.274 on single Yr gene lines and additional differentials, respectively. In total, 64 MLGs were detected among 113 isolates and the expected heterozygosity (He) was 0.424. A close genetic relationship was detected between Lufeng (Yunnan) / Nayong (Guizhou), Fuyuan (Yunnan) / Bijie (Guizhou), and Shizong (Yunnan) / Xingyi (Guizhou). This study provided useful information on population structure and virulence to Yr genes in the Yunnan and Guizhou epidemiological regions, and will be used to guide the control of wheat stripe rust and targeted wheat breeding in this region. [ABSTRACT FROM AUTHOR]

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 flg22 or nonpathogenic bacteria. Overexpression of Hasp98 in wheat (Triticum aestivum) suppressed avirulent Pst‐triggered immunity, leading to decreased H2O2 accumulation and promoting P. striiformis infection, whereas stable silencing of Hasp98 impaired P. striiformis pathogenicity. Hasp98 interacts with the wheat mitogen‐activated 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 Hasp98 inhibits 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. [ABSTRACT FROM AUTHOR]