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Leaf rust, caused by the pathogenic biotrophic rust fungus Puccinia triticina (Pt), is one of the most destructive wheat diseases worldwide; its negative impact on crop yields is exacerbated by increasing temperatures due to climate change. Ascarosides are nematode pheromones that induce resistance to microbial pathogens and pests in a wide range of crops, making them valuable components in biocontrol scenarios. We investigated the effect on infection of various wheat (Triticum aestivum) genotypes with the virulent Pt race 77W × R by ascr#18, the major ascaroside secreted into the rhizosphere by plant-parasitic nematodes. Spraying the leaves with ascr#18 24 h before inoculation with fungal uredospores slowed disease development and resulted in a reduction of the number of rust pustules on treated compared to untreated leaves. Dose–response analysis over the nano- and micromolar range revealed a broad optimum concentration down to 0.01nM ascr#18. Microscopic analysis showed very early arrest of the fungus at the appressorial stage, with associated enhanced local accumulation of H2O2 and abortive stoma penetration. Similarly, ascr#18 also induced strong resistance to Pt race PKTTS, confirming its race-unspecific biocontrol activity. The results of this study are consistent with and extend previous research that has shown that ascr#18 activates plant immunity and thus protects plants from pathogens even at very low doses. [ABSTRACT FROM AUTHOR]

Summary: Thaumatin‐like proteins (TLPs) in plants play a crucial role in combating stress, and they have been proven to possess antifungal properties. However, the role of TLPs in pathogens has not been reported.We identified a effector protein, Pt9029, which contained a Thaumatin domain in Puccinia triticina (Pt), possessing a chloroplast transit peptide and localized in the chloroplasts. Silencing Pt9029 in the Pt physiological race THTT resulted in a notable reduction in virulence and stunted growth and development of Pt hypha in near‐isogenic wheat line TcLr2b. Overexpression of Pt9029 in wheat exerted a suppressive effect on H2O2 production, consequently impeding the wheat's disease resistance mechanisms.The TLP domain of Pt9029 targets the Rubisco activase (TaRCA) in chloroplasts. This interaction effectively inhibited the function of TaRCA, subsequently leading to a decrease in Rubisco enzyme activity. Therefore, this indicates that TLPs in Pt can inhibit host defense mechanisms during the pathogenic process of Pt. Moreover, TaRCA silencing resulted in reduced resistance of TcLr2b against Pt race THTT.This clearly demonstrated that TaRCA positively regulates wheat resistance to leaf rust. These findings reveal a novel strategy exploited by Pt to manipulate wheat rust resistance and promote pathogenicity. [ABSTRACT FROM AUTHOR]

Nucleotide-binding leucine-rich repeat (NLR) disease resistance genes typically confer resistance against races of a single pathogen. Here, we report that Yr87/Lr85, an NLR gene from Aegilops sharonensis and Aegilops longissima, confers resistance against both P. striiformis tritici (Pst) and Puccinia triticina (Pt) that cause stripe and leaf rust, respectively. Yr87/Lr85 confers resistance against Pst and Pt in wheat introgression as well as transgenic lines. Comparative analysis of Yr87/Lr85 and the cloned Triticeae NLR disease resistance genes shows that Yr87/Lr85 contains two distinct LRR domains and that the gene is only found in Ae. sharonensis and Ae. longissima. Allele mining and phylogenetic analysis indicate multiple events of Yr87/Lr85 gene flow between the two species and presence/absence variation explaining the majority of resistance to wheat leaf rust in both species. The confinement of Yr87/Lr85 to Ae. sharonensis and Ae. longissima and the resistance in wheat against Pst and Pt highlight the potential of these species as valuable sources of disease resistance genes for wheat improvement. Leaf rust and stripe rust of wheat are two important fungal diseases of cultivated wheat and they are caused by infection of different pathogens. Here, the authors report the nucleotide-binding leucine-rich repeat (NLR) protein encoding gene Yr87/Lr85 confers resistance to both diseases. [ABSTRACT FROM AUTHOR]

Wheat (Triticum aestivum L.) leaf rust [Puccinia triticina (Pt)] causes devastating yield losses globally. Conceivably, breeding and development of cultivars harboring adult plant resistance (APR) to leaf rust (LR) can be an effective way to manage wheat leaf rust. Particularly, mapping of major quantitative trait loci (QTLs) facilitate breeding of LR resistant cultivars. Here, we have mapped QTLs for APR to LR in wheat using wheat population including 215 F2:3 lines from a Zhoumai 22/Chinese Spring. Bulked segregation analyse (BSA) and simple sequence repeat (SSR) detection of wheat lines digged out the QTLs for APR to LR. Using Manager QTXb20 and Icimapping 3.2 software, some APR QTLs were mapped in Zhoumai 22/Chinese Spring wheat population. Three QTLs of APR to LR detected and designated QLr.zh-2BS, QLr.zh-4BL and QLr.zh-7DS) explained 12.58–13.58%, 7.02–20.22% and 6.73–21.30% of the phenotypic variation, respectively. QLr.zh-4BL and QLr.zh-7DS were derived from Chinese Spring wheat, whereas QLr.zh-2BS emanated from Zhoumai 22. QLr.zh-4BL and QLr.zh-7DS were mapped close to Lr12 and Lr34, respectively, revealling their close link to these loci, correspondingly. Overall, the QTLs related APR to LR, their flanking markers and associated APR genes identified in this study could be useful to genomic resources and marker-assisted select breeding of LR resistance in wheat. [ABSTRACT FROM AUTHOR]

Stripe rust caused by Puccinia striiformis f. sp. tritici and leaf rust caused by Puccinia triticina, are two devastating diseases on wheat, which seriously affect the production safety of wheat. Timely detection and identification of the two diseases are essential for taking effective disease management measures to reduce wheat yield losses. To realize the accurate identification of wheat stripe rust and wheat leaf rust during the different growth stages, in this study, the image-based identification of wheat stripe rust and wheat leaf rust during different growth stages was investigated based on deep learning using image processing technology. Based on the YOLOv5s model, we built identification models of wheat stripe rust and wheat leaf rust during the seedling stage, stem elongation stage, booting stage, inflorescence emergence stage, anthesis stage, milk development stage, and all the growth stages. The models were tested on the different testing sets in the different individual growth stages and in all the growth stages. The results showed that the models performed differently in disease image identification. The model based on the disease images acquired during an individual growth stage was not suitable for the identification of the disease images acquired during the other individual growth stages, except for the model based on the disease images acquired during the milk development stage, which had acceptable identification performance on the testing sets in the anthesis stage and the milk development stage. In addition, the results demonstrated that wheat growth stages had a great influence on the image identification of the two diseases. The model built based on the disease images acquired in all the growth stages produced acceptable identification results. Mean F1 Score values between 64.06% and 79.98% and mean average precision (mAP) values between 66.55% and 82.80% were achieved on each testing set composed of the disease images acquired during an individual growth stage and on the testing set composed of the disease images acquired during all the growth stages. This study provides a basis for the image-based identification of wheat stripe rust and wheat leaf rust during the different growth stages, and it provides a reference for the accurate identification of other plant diseases. [ABSTRACT FROM AUTHOR]

Wheat leaf rust caused by Puccinia triticina (Pt) is an important disease of bread wheat in Zimbabwe. This study was carried out to determine the distribution, avirulence/virulence profile(s) and genotypic variation among isolates of the pathogen. In total, 104 single-pustule isolates were established from infected wheat samples that were collected from the main wheat production regions in Zimbabwe in surveys conducted from 2019 to 2021. Phenotyping of the isolates on a set of 46 differential and additional wheat lines revealed a single Pt race, MCDS. For genotypic assessment, 48 Pt isolates, including eight South African races, were genotyped with 19 microsatellite markers. Using the Bayesian model, isolates were subdivided into three clusters in both a DARwin neighbour-joining tree and STRUCTURE analysis. The results confirmed a high genetic similarity between the Zimbabwean Pt isolates and the South African races MCDS, MCPS and MFPS. Furthermore, Pt isolates from Zimbabwe were clonal, which was in accordance with all 104 isolates that typed to race MCDS. [ABSTRACT FROM AUTHOR]

SUMMARY: Hypersensitive response‐programmed cell death (HR‐PCD) regulated by Ca2+ signal is considered the major regulator of resistance against Puccinia triticina (Pt.) infection in wheat. In this study, the bread wheat variety Thatcher and its near‐isogenic line with the leaf rust resistance locus Lr26 were infected with the Pt. race 260 to obtain the compatible and incompatible combinations, respectively. The expression of translationally controlled tumor protein (TaTCTP) was upregulated upon infection with Pt., through a Ca2+‐dependent mechanism in the incompatible combination. The knockdown of TaTCTP markedly increased the area of dying cell and the number of Pt. haustorial mother cells (HMCs) at the infection sites, whereas plants overexpressing the gene exhibited enhanced resistance. The interaction between TaTCTP and calcineurin B‐like protein‐interacting protein kinase 23 (TaCIPK23) was also investigated, and the interaction was found occurred in the endoplasmic reticulum. TaCIPK23 phosphorylated TaTCTP in vitro. The expression of a phospho‐mimic TaTCTP mutant in Nicotiana benthamiana promoted HR‐like cell death. Silencing TaCIPK23 or TaCIPK23/TaTCTP co‐silencing resulted in the same results as silencing TaTCTP. This suggested that TaTCTP is a novel phosphorylation target of TaCIPK23, and both participate in the resistance of wheat to Pt. in the same pathway. Significance Statement: Wheat leaf rust caused by Puccinia triticina infection causes losses to agriculture worldwide. Calcium signaling and its mediated hypersensitive response are critical for leaf rust resistance in wheat. By demonstrating the phosphorylation of TaTCTP by TaCIPK23 and their contribution to the leaf rust resistance phenotype in wheat, this study reveals the mechanism by which calcium mediates biotic stress resistance and provides valuable insights for future crop improvement strategies. [ABSTRACT FROM AUTHOR]

Wheat leaf rust, caused by Puccinia triticina, poses a growing threat to global wheat production, necessitating alternative strategies for effective disease management. This study investigated the potential of gamma-aminobutyric acid (GABA) to enhance resistance to leaf rust in two wheat cultivars: the susceptible Morocco and moderately resistant Sakha 94 cultivar. Our findings revealed that GABA significantly improved resistance in both cultivars to P. triticina, particularly in Morocco, by mitigating disease severity and reducing pustule density and size while extending both incubation and latent periods. This study assessed the effectiveness of two GABA application methods: plants received 1 mM GABA treatment, as a foliar spray, twenty-four hours prior to infection (pre-GABA), and plants received 1 mM GABA treatment both 24 h before and after infection (pre-/post-GABA), with the latter yielding significantly better results in reducing infection severity and improving plant resilience. Additionally, GABA application influenced stomatal behavior, promoting closure that may enhance resilience against leaf rust. GABA application on plants also modulated the production of reactive oxygen species (ROS). This led to a stronger oxidative burst in both susceptible and moderately resistant cultivars. GABA increased O2●− levels in guard cells and surrounding stomata, enhancing stomatal closure and the hypersensitive response. GABA enhanced the accumulation of soluble phenols and increased the activity of key antioxidant enzymes, catalase (CAT) and peroxidase (POX), which are vital for managing oxidative stress. To the best of our knowledge, this investigation represents the first report into the impact of GABA on wheat leaf rust disease. [ABSTRACT FROM AUTHOR]

Leaf rust (Puccinia triticina) is a common disease that causes significant yield losses in wheat. The most frequently used methods to control leaf rust are the application of fungicides and the cultivation of resistant genotypes. However, high genetic diversity and associated adaptability of pathogen populations hamper achieving durable resistance in wheat. Emerging alternatives, such as microbial priming, may represent an effective measure to stimulate plant defense mechanisms and could serve as a means of controlling a broad range of pathogens. In this study, 175 wheat genotypes were inoculated with two bacterial strains: Ensifer meliloti strain expR+ch (producing N-acyl homoserine lactone (AHL)) or transformed E. meliloti carrying the lactonase gene attM (control). In total, 21 genotypes indicated higher resistance upon bacterial AHL priming. Subsequently, the phenotypic data of 175 genotypes combined with 9917 single-nucleotide polymorphisms (SNPs) in a genome-wide association study to identify quantitative trait loci (QTLs) and associated markers for relative infection under attM and expR+ch conditions and priming efficiency using the Genome Association and Prediction Integrated Tool (GAPIT). In total, 15 QTLs for relative infection under both conditions and priming efficiency were identified on chromosomes 1A, 1B, 2A, 3A, 3B, 3D, 6A, and 6B, which may represent targets for wheat breeding for priming and leaf-rust resistance. [ABSTRACT FROM AUTHOR]

Leaf rust caused by Puccinia triticina (Pt) is one of the most impactful diseases causing substantial losses in common wheat (Triticum aestivum L.) crops. In adult plants resistant to Pt, a horizontal adult plant resistance (APR) is observed: APR protects the plant against multiple pathogen races and is distinguished by durable persistence under production conditions. The Lr46/Yr29 locus was mapped to chromosome 1B of common wheat genome, but the identity of the underlying gene has not been demonstrated although several candidate genes have been proposed. This study aimed to analyze the expression of nine candidate genes located at the Lr46/Yr29 locus and their four complementary miRNAs (tae-miR5384-3p, tae-miR9780, tae-miR9775, and tae-miR164), in response to Pt infection. The plant materials tested included five reference cultivars in which the molecular marker csLV46G22 associated with the Lr46/Yr29-based Pt resistance was identified, as well as one susceptible control cultivar. Biotic stress was induced in adult plants by inoculation with fungal spores under controlled conditions. Plant material was sampled before and at 6, 12, 24, 48 hours post inoculation (hpi). Differences in expression of candidate genes at the Lr46/Yr29 locus were analyzed by qRT-PCR and showed that the expression of the genes varied at the analyzed time points. The highest expression of Lr46/Yr29 candidate genes (Lr46-Glu1, Lr46-Glu2, Lr46-Glu3, Lr46-RLK1, Lr46-RLK2, Lr46-RLK3, Lr46-RLK4, Lr46-Snex, and Lr46-WRKY) occurred at 12 and 24 hpi and such expression profiles were obtained only for one candidate gene among the nine genes analyzed (Lr46-Glu2), indicating that it may be a contributing factor in the resistance response to Pt infection. [ABSTRACT FROM AUTHOR]

Leaf rust is a widespread foliar wheat disease causing substantial yield losses worldwide. Slow rusting is "adult plant" resistance that significantly slows epidemic development and thereby reduces yield loss. Wheat accession CI 13227 was previously characterized as having slow-rusting resistance. To validate the quantitative trait loci (QTLs) and develop diagnostic markers for slow rusting resistance in CI 13227, a new population of recombinant inbred lines of CI 13227 × Everest was evaluated for latent period, final severity, area under the disease progress curve, and infection type in greenhouses and genotyped using genotyping-by-sequencing. Four QTLs were identified on chromosome arms 2BL, 2DS, 3BS, and 7BL, explaining 6.82 to 28.45% of the phenotypic variance for these traits. Seven kompetitive allele-specific polymorphism markers previously reported to be linked to the QTLs in two other CI 13227 populations were validated. In addition, the previously reported QLr.hwwg-7AL was remapped to 2BL (renamed QLr.hwwg-2BL) after adding new markers in this study. Phenotypic data showed that the recombinant inbred lines harboring two or three of the QTLs had a significantly longer latent period. QLr.hwwg-2DS on 2DS showed a major effect on all rust resistance traits and was finely mapped to a 2.7-Mb interval by two newly developed flanking markers from exome capture. Three disease-resistance genes and two transporter genes were identified as the putative candidates for QLr.hwwg-2DS. The validated QTLs can be used as slow-rusting resistance resources, and the markers developed in this study will be useful for marker-assisted selection. [ABSTRACT FROM AUTHOR]

Spring bread wheat (Triticum aestivum) is a major crop in Russia and in Kazakhstan. The rust pathogens, leaf rust caused by the fungus Puccinia triticina, stem rust incited by P. graminis and yellow rust caused by P. striiformis, are the significant biotic factors affecting wheat production. In this study, 40 new promising spring wheat genotypes from the Kazakhstan-Siberia Network for Spring Wheat Improvement (KASIB) were tested for resistance to leaf, stem and yellow rust at the seedling stage, and for identification of rust resistance genes using molecular markers. In addition, the collection was tested for leaf rust resistance and grain yields in the South Urals agroclimatic zone of Russia in 2023. As a result, 16 accessions with seedling resistance to leaf rust, 21 to stem rust and 4 to yellow rust were identified. Three breeding accessions were resistant to all rust species, and nine to P. triticina and P. graminis. Wheat accessions resistant to leaf rust at the seedling stage were also resistant in the field. Molecular analysis showed the presence of cataloged resistance genes, Lr1, Lr3a, Lr9, Lr10, Lr19, Lr20, Lr24, Lr26, Sr15, Sr24, Sr25, Sr31, Sr38, Yr9 and Yr18; uncatalogued genes Lr6Agi1 and Lr6Agi2 from Thinopyrum intermedium and LrAsp from Aegilops speltoides; and 1AL.1RS translocation. The current analysis showed an increase in leaf and stem rust resistance of new KASIB genotypes and their genetic diversity due to the inclusion of alien genetic material in breeding. [ABSTRACT FROM AUTHOR]

Wheat leaf rust, caused by Puccinia triticina, is one of the most common fungal diseases of wheat in China and occurs widely in various wheat-growing regions. To clarify the epidemic, spread rules, and population structure of P. triticina among different regions, 217 isolates of P. triticina collected from Hebei, Shandong, Sichuan, and Xinjiang in China were tested by 34 Thatcher near-isogenic lines and 21 pairs of EST-SSR primers. A total of 83 races were identified, and THTT, PHTT, THTS, and PHJT were the most predominant races in the four provinces in 2009. We found enriched virulence and genetic diversity in the four P. triticina populations and a significant correlation between genetic polymorphism and geographic regions. However, no significant correlation was found between virulence phenotypes and molecular genotypes. Moreover, a notable high level of gene flow (Nm = 2.82 > 1) among four P. triticina populations was detected. The genetic relationship among Hebei, Shandong, and Sichuan populations was close, possibly due to the spread of P. triticina from Sichuan to Shandong and then to Hebei. In contrast, the Xinjiang population was relatively independent. Genetic differentiation analysis showed some level of differentiation among or within populations of P. triticina in the four provinces, and the genetic variation within populations (74.97%) was higher than across populations (25.03%). Our study provides a basis for a better understanding of the regional migration, epidemic, and population structure of P. triticina in China. [ABSTRACT FROM AUTHOR]

Wheat leaf rust fungus is an obligate parasitic fungus that can absorb nutrients from its host plant through haustoria and secrete effector proteins into host cells. The effector proteins are crucial factors for pathogenesis as well as targets for host disease resistance protein recognition. Exploring the role of effector proteins in the pathogenic process of Puccinia triticina Eriks. (Pt) is of great significance for unraveling its pathogenic mechanisms. We previously found that a cysteine-rich effector protein, Pt1641, is highly expressed during the interaction between wheat and Pt, but its specific role in pathogenesis remains unclear. Therefore, this study employed techniques such as heterologous expression, qRT-PCR analysis, and host-induced gene silencing (HIGS) to investigate the role of Pt1641 in the pathogenic process of Pt. The results indicate that Pt1641 is an effector protein with a secretory function and can inhibit BAX-induced programmed cell death in Nicotiana benthamiana. qRT-PCR analyses showed that expression levels of Pt1641 were different during the interaction between the high-virulence strain THTT and low-virulence strains FGD and Thatcher, respectively. The highest expression level in the low-virulence strain FGD was four times that of the high-virulence strain THTT. The overexpression of Pt1641 in wheat near-isogenic line TcLr1 induced callose deposition and H2O2 production on TcLr1. After silencing Pt1641 in the Pt low-virulence strain FGD on wheat near-isogenic line TcLr1, the pathogenic phenotype of Pt physiological race FGD on TcLr1 changed from ";" to "3", indicating that Pt1641 plays a non-toxic function in the pathogenicity of FGD to TcLr1. This study helps to reveal the pathogenic mechanism of wheat leaf rust and provides important guidance for the mining and application of Pt avirulent genes. [ABSTRACT FROM AUTHOR]

We detected isolates with SdhC-I87F-conferring mutations that were slightly SDHI-adapted in the barley leaf rust Puccinia hordei in France and the UK in 2019. SdhC-I87F of P. hordei is orthologous to SdhC-I86F in Phakopsora pachyrhizi, and SdhC-I88F in Puccinia horiana induced SDHI resistance. Nevertheless, the field performance of SDHIs against P. hordei was good, although strains with SdhC-I87F dominated the field. The sensitivity ranges were narrow for wheat leaf rust and Puccinia triticina in 2019; however, isolates with slightly higher EC50 values were obtained in southern France and the eastern UK in 2021. These isolates of P. triticina harbored an orthologous SdhC-I87F-conferring mutation. The range of EC50 values for the SDHI fungicide inpyrfluxam overlapped between the wild type and SdhC-I87F isolates. Further analyses are currently underway. [ABSTRACT FROM AUTHOR]

One of the biggest obstacles to increasing wheat production and yield is diseases. Diseases not only reduce the amount of product but also negatively affect product quality. Rust diseases in wheat are among the most important biotic stress factors limiting wheat production in our country. In epidemic years, early infections on cereals susceptible varieties can cause yield losses of up to 80-90% and can cause varieties to be completely removed from production. In our country, yield losses caused by different types of rust on wheat plants have been recorded between 12-80%. Product losses vary depending on the sensitivity of varieties, environmental conditions, and the races of the factors, as well as from year to year and from region to region. Leaf rust (Lr) (Puccinia triticina Eriks.) is seen almost everywhere wheat is grown, but the damage it causes is not as noticeable as the damage caused by black and yellow rust. However, these two rust agents are not effective every year and cause serious epidemics every 7-8 years. Leaf rust, on the other hand, occurs almost every year and causes a certain amount of yield loss. The most important method for creating broad-spectrum disease resistance in cereals is the combined use of biotechnology and traditional breeding methods. [ABSTRACT FROM AUTHOR]

Effectors are considered to be virulence factors secreted by pathogens, which play an important role during host-pathogen interactions. In this study, the candidate effector Pt9226 was cloned from genomic DNA of Puccinia triticina (Pt) pathotype THTT, and there were six exons and five introns in the 877 bp sequence, with the corresponding open reading frame of 447 bp in length, encoding a protein of 148 amino acids. There was only one polymorphic locus of I142V among the six Pt pathotypes analyzed. Bioinformatics analysis showed that Pt9226 had 96.46% homology with the hypothetical putative protein PTTG_26361 (OAV96349.1) in the Pt pathotype BBBD. RT-qPCR analyses showed that the expression of Pt9226 was induced after Pt inoculation, with a peak at 36 hpi, which was 20 times higher than the initial expression at 0 hpi, and another high expression was observed at 96 hpi. No secretory function was detected for the Pt9226-predicted signal peptide. The subcellular localization of Pt9226Δsp-GFP was found to be multiple, localized in the tobacco leaves. Pt9226 could inhibit programmed cell death (PCD) induced by BAX/INF1 in tobacco as well as DC3000-induced PCD in wheat. The transient expression of Pt9226 in 26 wheat near-isogenic lines (NILs) by a bacterial type III secretion system of Pseudomonas fluorescens EtHAn suppressed callose accumulation triggered by Ethan in wheat near-isogenic lines TcLr15, TcLr25, and TcLr30, and it also suppressed the ROS accumulation in TcLr15. RT-qPCR analysis showed that the expression of genes coded for pathogenesis-related protein TaPR1, TaPR2, and thaumatin-like protein TaTLP1, were suppressed, while the expression of PtEF-1α was induced, with 1.6 times at 72 h post inoculation, and TaSOD was induced only at 24 and 48 h compared with the control, when the Pt pathotype THTT was inoculated on a transient expression of Pt9226 in wheat TcLr15. Combining all above, Pt9226 acts as a virulence effector in the interaction between the Pt pathotype THTT and wheat. [ABSTRACT FROM AUTHOR]

Background: Powdery mildew (caused by Blumeria graminis f. sp. tritici (Bgt)) and leaf rust (caused by Puccinia triticina (Pt)) are prevalent diseases in wheat (Triticum aestivum L.) production. Thinopyrum ponticum (2n = 10x = 70, EeEeEbEbExExStStStSt) contains genes that confer high levels of resistance to these diseases. Results: An elite wheat-Th. ponticum disomic substitution line, DS5Ag(5D), was developed in the Bainong Aikang 58 (AK58) background. The line was assessed using genomic in situ hybridization (GISH), oligo-nucleotide probe multiplex (ONPM) fluorescence in situ hybridization (FISH), and molecular markers. Twenty eight chromosome-specific molecular markers were identified for the alien chromosome, and 22 of them were co-dominant. Additionally, SNP markers from the wheat 660 K SNP chip were utilized to confirm chromosome identification and they provide molecular tools for tagging the chromosome in concern. The substitution line demonstrated high levels of resistance to powdery mildew throughout its growth period and to leaf rust at the adult stage. Based on the resistance evaluation of five F5 populations between the substitution lines and wheat genotypes with different levels of sensitivity to the two diseases. Results showed that the resistance genes located on 5Ag confered stable resistance against both diseases across different backgrounds. Resistance spectrum analysis combined with diagnostic marker detection of known resistance genes of Th. ponticum revealed that 5Ag contained two novel genes, Pm5Ag and Lr5Ag, which conferred resistance to powdery mildew and leaf rust, respectively. Conclusions: In this study, a novel wheat-Th. ponticum disomic substitution line DS5Ag(5D) was successfully developed. The Th. ponticum chromosome 5Ag contain new resistance genes for powdery mildew and leaf rust. Chromosomic—specific molecular markers were generated and they can be used to track the 5Ag chromosome fragments. Consequently, this study provides new elite germplasm resources and molecular markers to facilitate the breeding of wheat varieties that is resistant to powdery mildew and leaf rust. [ABSTRACT FROM AUTHOR]

Employing race‐specific resistance genes remains an effective strategy to protect wheat from leaf rust caused by Puccinia triticina (Pt) worldwide, while the newly emerged Pt races, owing to rapid genetic evolution, frequently overcome the immune response delivered by race‐specific resistance genes. The molecular mechanisms underlying the newly evolved virulence Pt pathogen remain unknown. Here, we identified an avirulence protein AvrLr15 from Pt that induced Lr15‐dependent immune responses. Heterologously produced AvrLr15 triggered pronounced cell death in Lr15‐isogenic wheat leaves. AvrLr15 contains a functional signal peptide, localized to the plant nucleus and cytosol and can suppress BAX‐induced cell death. Evasion of Lr15‐mediated resistance in wheat was associated with a deletion and point mutations of amino acids in AvrLr15 rather than AvrLr15 gene loss in the Lr15‐breaking Pt races, implying that AvrLr15 is required for the virulence function of Pt. Our findings identified the first molecular determinant of wheat race‐specific immunity and facilitated the identification of the first AVR/R gene pair in the Pt–wheat pathosystem, which will provide a molecular marker to monitor natural Pt populations and guide the deployment of Lr15‐resistant wheat cultivars in the field. [ABSTRACT FROM AUTHOR]

Genetic resistance is the most economical and efficient way to reduce production losses brought on by diseases. Plant breeders continuously incorporate new, dependable sources into their breeding materials to continue developing disease-resistant genotypes. Fourteen certified wheat (Triticum aestivum L.) cultivar (Bahawalpur-2000, NIFA-Bathor08, Fareed-2006, Haider-2002, Imdad-2005, Lasani-2008, Marvi-2000, Moomal-2000, Manther-2003, Pirsabak-2006, Iqbal-2000, Pirsabak-2004, Shahkar-2013, and Wafaq-2002) seeds from the Nuclear Institute for Food and Agriculture (NIFA) and National Agriculture Research Center (NARC) were grown in pots. DNA obtained from fresh leaves of the wheat cultivars were screened for leaf rust resistance genes (i.e. Lr-51, Lr-47, Lr-46, Lr-37, Lr-36, Lr-35, Lr-34, Lr-28, Lr-25, Lr-19, Lr-13, Lr-9, and Lr-1 using PCR. Results showed that the Lr-47 gene was present in nine wheat cultivars, Lr-1 and Lr-28 in eight, Lr-5, Lr-9, and Lr-13 in three, and Lr-19 and Lr-37 in one cultivar. In the selected wheat cultivars, the resistance genes Lr-25, Lr-35, Lr-36, and Lr-46 were not observed. This study suggests cultivating wheat varieties Haider-2002, Iqbal-2000, Lasani-2008, Manther-2003, Pirsbak-2004, Pirsbak-2006, Shahkar-2013, and Wafaq-2002 for high level of resistance to rust and protection against high production losses. In future studies, phenotypic data alongside genotypic screening will improve the assessment of leaf rust resistance in wheat cultivars, leading to a better understanding of their disease resistance profiles. [ABSTRACT FROM AUTHOR]

Leaf rust, caused by the fungus Puccinia triticina Eriks (Pt), is a destructive disease affecting wheat (Triticum aestivum L.) production in many countries, and a serious threat to food security. As a result, several breeding programs have included leaf rust resistance as an important trait. The discovery and identification of new resistance genes that could aid in incorporating durable or long-lasting leaf rust resistance into wheat is fundamental in these breeding programs. The present study aimed to identify quantitative trait loci (QTLs) for leaf rust resistance in 127 recombinant inbred lines (RIL) developed from the cross between the resistant wheat cultivar Popo and the susceptible cultivar Kariega. The RIL population and parental lines were phenotyped for leaf rust infection type and severity at seedling and adult plant stage, respectively. The former in the greenhouse (in Argentina) and the latter in multiple field test environments comprising 3 locations in South Africa (in Tygerhoek in the Western Cape Province during the 2014, 2015, 2017 and 2018 cropping seasons; Clarens during 2014, 2016 and 2017 cropping seasons and in Bethlehem in the Free State Province during 2017 cropping season) and in 1 location in Argentina (during the 2017 and 2018 cropping seasons in Marcos Juárez, Córdoba Province). The population was genotyped using genotyping-by-sequencing. A total of 12,080 silicoDArT and 2,669 SNP markers were used for QTL analysis. In total, 25 putative QTLs for resistance to leaf rust at seedling and adult plant stages were identified, including 5 QTLs for seedling and 20 QTLs for adult plant resistance (APR). Interestingly, both Popo and Kariega contributed with alleles for resistance. Significant loci for reducing leaf rust infection at seedling stage were designated QLr.arc-1A, QLr.arc-2B, QLr.arc-5B, QLr.arc-6A and QLr.arc-6D. Three minor QTLs derived from Popo designated as QLr.arc-1B1, QLr.arc-2D and QLr.arc-3D were also detected from the field tests, explaining 5–10%, 10–16% and 5–7% of the phenotypic variance, respectively. The identified QTLs and their closely linked silicoDArT and SNP-based markers can be used for fine mapping and candidate gene discovery in wheat breeding programs targeting durable leaf rust resistance.

Leaf rust, caused by Puccinia triticina, is a major cause of wheat yield losses globally, and novel leaf rust resistance genes are needed to enhance wheat leaf rust resistance. Teremai Bugdai is a landrace from Uzebekistan that is highly resistant to many races of P. triticina in the United States. To unravel leaf rust resistance loci in Teremai Bugdai, a recombinant inbred line (RIL) population of Teremai Bugdai × TAM 110 was evaluated for response to P. triticina race Pt54-1 (TNBGJ) and genotyped using single nucleotide polymorphism (SNP) markers generated by genotyping-by-sequencing (GBS). Quantitative trait loci (QTL) analysis using 5,130 high-quality GBS-SNPs revealed three QTLs, QLr-Stars-2DS, QLr-Stars-6BL, and QLr. Stars-7BL, for leaf rust resistance in two experiments. QLr-Stars-2DS, which is either a new Lr2 allele or a new resistance locus, was delimited to an ~19.47-Mb interval between 46.4 and 65.9 Mb on 2DS and explained 31.3 and 33.2% of the phenotypic variance in the two experiments. QLr-Stars-6BL was mapped in an ~84.0-kb interval between 719.48 and 719.56 Mb on 6BL, accounting for 33 to 36.8% of the phenotypic variance in two experiments. QLr. Stars-7BL was placed in a 350-kb interval between 762.41 and 762.76 Mb on 7BL and explained 4.4 to 5.3% of the phenotypic variance. Nine GBS-SNPs flanking these QTLs were converted to kompetitive allele specific PCR (KASP) markers, and these markers can be used to facilitate their introgression into locally adapted wheat lines. [ABSTRACT FROM AUTHOR]

The near-isogenic lines (66) and wheat cultivars/germplasm (20) carrying known leaf rust resistance genes along with susceptible checks (BWL 4444, HD 3086 and Agra local) were evaluated against leaf rust of wheat at four different locations across Punjab, India [Ludhiana (West), Gurdaspur, Abohar, Langroya (SBS Nagar)]. The genes namely Lr9, Lr19, Lr24, Lr28, Lr42, Lr45, Lr47, Lr52, Lr57, Lr58, Lr76 were found effective in Punjab (India) against the most prevalent pathotypes of leaf rust pathogen [77-9 (121R60-1), 121R60-1,7 and 77-5 (121R63-1)]. These genes can be deployed singly or in combination for successful management of leaf rust. The disease severity was comparatively less at Abohar. So, the correlation of disease severity with environmental factors (maximum temperature, minimum temperature, relative humidity and total rainfall) were worked out and found highly significant. Strong positive correlation of disease severity with minimum temperature (0.86) followed by moderate positive correlation with rainfall (0.54) was observed. Disease severity level was higher when 25.4–28.3 °C maximum temperature; 13.8–15.7 °C minimum temperature coupled with relative humidity of 67–71% and rainfall in the range of 9–21 mm prevails during the months of February–March. [ABSTRACT FROM AUTHOR]

The paper reports the research performed to characterize resistance to leaf and yellow rusts in promising soft spring wheat accessions and to evaluate their diversity for the Lr and Yr resistance genes to identify valuable genotypes. The material for the study included 36 new varieties and lines (23 from Russia and 13 from Kazakhstan). Seedling resistance was evaluated under laboratory conditions using single pustule isolates and populations with different virulence. Resistance to leaf rust in the seedling stage was demonstrated by 42% of accessions. Using gene-specific PCR markers, 20 Lr genes were postulated. Isogenic Thatcher lines bearing the genes under study served as positive controls. The authors identified in the spring wheat samples highly efficient in Russia and Kazakhstan genes Lr24 (three accessions) and LrAgi2 (three accessions); genes Lr9 (four accessions) and Lr19 (six accessions), which have partially lost their efficiency; genes Lr1 (seven accessions), Lr3 (thirteen accessions), Lr10 (four accessions), Lr26 (12 accessions), and Lr34 (four accessions) with low efficiency; and the wheat–rye translocation 1AL.1RS (four accessions) containing leaf, stem, and yellow rust resistance genes. The resistant samples carried two or more Lr genes each. Phytopathological tests did not reveal any accessions that would be highly resistant to all used regional populations of the yellow rust pathogen. Genotyping with molecular markers did not reveal accessions containing highly efficient Yr5, Yr10, Yr15, Yr17, and Yr24 genes. Ineffective genes Yr9 and Yr18 were identified in 30 and 8% of lines, respectively. The results of the analysis indicate success in breeding for resistance to leaf rust and the need for advanced breeding for resistance to yellow rust using effective donors. [ABSTRACT FROM AUTHOR]

Overall, there is a major wish that European farmers implement integrated pest management (IPM), particularly to reduce dependence on pesticides. In the European Rustwatch project, partners conducted nineteen trials across nine different countries during 2020 and 2021 to investigate different IPM strategies, focusing on controlling rust diseases in winter wheat. The trials included the use of varieties with contrasting levels of resistance, variety mixtures, reduced fungicide rates, thresholds, and Decision Support Systems (DSSs), and testing alternative products to fungicides. Sixteen trials developed yellow rust (Puccinia striiformis f. sp. tritici) infections, and six trials developed brown rust (Puccinia triticina) infections. Resistant varieties proved highly effective in keeping down yellow rust infection, and variety mixtures also effectively reduced infection levels and stabilized yields. Rust was fully controlled using 25% of standard fungicide rates, even under high disease pressure. Using DSSs provided sufficient control of rust diseases and resulted in competitive net economic returns due to fewer fungicide applications. The alternative products tested included two biological control agents and four alternative chemistries, which all gave inferior and insufficient control against rust compared with chemical fungicides. The trial work demonstrated that there are good and reliable options for including IPM into disease control in wheat. [ABSTRACT FROM AUTHOR]

The F-box proteins in fungi perform diverse functions including regulation of cell cycle, circadian clock, development, signal transduction and nutrient sensing. Genome-wide analysis revealed 10 F-box genes in Puccinia triticina, the causal organism for the leaf rust disease in wheat and were characterized using in silico approaches for revealing phylogenetic relationships, gene structures, gene ontology, protein properties, sequence analysis and gene expression studies. Domain analysis predicted functional domains like WD40 and LRR at C-terminus along with the obvious presence of F-box motif in N-terminus. MSA showed amino acid replacements, which might be due to nucleotide substitution during replication. Phylogenetic analysis revealed the F-box proteins with similar domains to be clustered together while some sequences were spread out in different clades, which might be due to functional diversity. The clustering of Puccinia triticina GG705409 with Triticum aestivum TaAFB4/TaAFB5 in a single clade suggested the possibilities of horizontal gene transfer during the coevolution of P. triticina and wheat. Gene ontological annotation categorized them into three classes and were functionally involved in protein degradation through the protein ubiquitination pathway. Protein–protein interaction network revealed F-box proteins to interact with other components of the SCF complex involved in protein ubiquitination. Relative expression analysis of five F-box genes in a time course experiment denoted their involvement in leaf rust susceptible wheat plants. This study provides information on structure elucidation of F-box proteins of a basidiomycetes plant pathogenic fungi and their role during pathogenesis. [ABSTRACT FROM AUTHOR]

Leaf rust, caused by Puccinia triticina (Pt), is a major disease of wheat and a significant problem for wheat production in Brazil. The Brazilian variety Toropi, released in 1965, has maintained high levels of field, adult plant resistance (APR) to leaf rust across global locations, while microscopic studies have indicated prehaustorial resistance mechanisms. Analyses of gene expression in flag leaves of Toropi, during the early stages of Pt infection, were undertaken to explore the mechanisms behind the APR in Toropi. Differential expression of wheat genes was undertaken, comparing Pt‐ to mock‐inoculated and Pt‐ to Pt‐inoculated time points. Analysis of gene expression indicated a strong response to Pt, which was fully active by 6 h after inoculation (hai). More genes were downregulated than upregulated, particularly at 6 and 12 hai. Gene Ontology enrichment analysis indicated a shutting down of RNA and protein synthesis and an early effect on photosynthesis, with disruption of the electron transfer chain. Analyses of upregulated genes identified genes involved in ATP‐binding and protein kinase activity at 6 hai, supporting a rapid metabolic response to Pt infection. A general upregulation of genes involved in transport and metabolism indicated the need to relocate protein and organic‐based resources. Alignment of differentially expressed genes with the genomic regions defining four leaf rust APR quantitative trait loci (QTLs) in Toropi identified candidate resistance genes, including a sugar transporter, a receptor kinase and a seven‐transmembrane MLO family protein. In addition, 60 Pt genes were identified, 11 being annotated as potential effector proteins. [ABSTRACT FROM AUTHOR]

Leaf rust caused by the pathogen Puccinia triticina (Pt) is a destructive fungal disease of wheat that occurs in almost all wheat-growing areas across the globe. Genetic resistance has proven to be the best solution to mitigate the disease. Wheat breeders are continuously seeking new diversified and durable sources of resistance to use in developing new varieties. We developed recombinant inbred line (RIL) populations from two leaf rust-resistant genotypes (Kenya Kudu and AUS12568) introduced from Kenya to identify and characterize resistance to Pt and to develop markers linked closely to the resistance that was found. Our studies detected four QTL conferring adult plant resistance (APR) to leaf rust. Two of these loci are associated with known genes, Lr46 and Lr68, residing on chromosomes 1B and 7B, respectively. The remaining two, QLrKK_2B and QLrAus12568_5A, contributed by Kenya Kudu and AUS12568 respectively, are putatively new loci for Pt resistance. Both QLrKK_2B and QLrAus12568_5A were found to interact additively with Lr46 in significantly reducing the disease severity at adult plant growth stages in the field. We further developed a suite of six closely linked markers within the QLrAus12568_5A locus and four within the QLrKK_2B region. Among these, markers sunKASP_522 and sunKASP_524, flanking QLrAus12568_5A, and sunKASP_536, distal to QLrKK_2B, were identified as the most closely linked and reliable for marker-assisted selection. The markers were validated on a selection of 64 Australian wheat varieties and found to be polymorphic and robust, allowing for clear allelic discrimination. The identified new loci and linked molecular markers will enable rapid adoption by breeders in developing wheat varieties carrying diversified and durable resistance to leaf rust. [ABSTRACT FROM AUTHOR]

Background and Objectives Brown rust, or leaf rust, of wheat, caused by Puccinia triticina Eriks., is one of the most damaging diseases affecting wheat worldwide, including in Iran. Under epidemic conditions, brown rust can reduce wheat yields by 20 to 50%. This disease's impact is exacerbated by the fungus's sexual cycle and the resulting new genetic recombinations, which occur in regions where intermediate hosts are present. Additionally, the fungus's asexual cycle thrives under favorable weather conditions. The high genetic diversity and flexibility of Puccinia triticina, driven by mutation, migration, and selection pressure from host resistance genes, enable the production of new physiological races that can overcome existing genetic resistance. These new races can rapidly spread between regions via wind, increasing racial diversity in other areas' disease populations. The most reliable and fundamental method for controlling and managing brown rust is through genetic resistance. Accurate knowledge of the pathogenic population's genetic structure in each region is essential for developing effective and stable genetic resistance in wheat. This can be achieved by monitoring harmful pathogenic factors using differential genotypes of brown rust in trap nurseries. Materials and Methods The effectiveness of resistance genes in international differential cultivars of brown rust was investigated in the Moghan region of Ardabil Province, a major wheat production area in Iran, over two consecutive crop years (2022-2023). To identify resistance sources against the local races of brown rust, the responses of 40 commercial wheat varieties and 40 promising wheat lines were evaluated. Resistance was assessed at the full plant stage under natural infection conditions. Parameters measured included the coefficient of infection (CI), final disease severity (FDS), and the relative value of the area under the disease progress curve (rAUDPC). These evaluations were conducted at the research station of the Research and Training Center for Agriculture and Natural Resources of Ardabil Province (Moghan). Results The populations of brown rust races in the Moghan region varied between the two years studied. The results indicated that the pathogenic fungus population in both years was resistant to differential cultivars carrying the resistance genes Lr18, Lr19, Lr20, Lr22a, and Lr29. Thus, these genes were effective in providing resistance against brown rust pathogenic races in the Moghan region. Additionally, differential cultivars with resistance genes Lr2a, Lr2b, Lr9, Lr17, Lr21, Lr23, Lr10/Lr27/Lr31, Lr33, and Lr34 demonstrated relatively acceptable resistance to the brown rust pathogenic strains in the Ardabil region. The resistance reactions of these genotypes were race- specific, showing resistance in one year and semi-resistant to semi-sensitive reactions with 5-20% infection intensity in another year. Commercial cultivars and promising wheat lines that exhibited effective resistance and the lowest values for the measured traits were identified as sources of effective genetic resistance to the brown rust pathogenic population in the Moghan region and similar hot and humid climates in the country. These include the cultivars Sahar, Rakhshan, Shush, Farin, Sirvan, Araz, Meraj, Danesh, Talai, Sana, Aran, Tirgan, Taban, Hana, Mehrgan, Avan, Arman, Fallah, and Tektaz, as well as the lines N-95-6, N-98-8, S-95-3, S-96-15, S-96-16, S-97- 10, S-98-11, S-98-22, M-97-12, M-97-18, M-98-18, CD-91-12, C-97-4, CD-97-19, C-98-7, C-98- 8, CD-98-17, MS-92-5, MS-94-5, D-97-15, and D-97-16. Discussion Correct and conscious use of the effective resistance genes identified in this research can foster more stable resistance to brown rust. The resistance genes present in the identified resistant genotypes can be utilized in multi-breeding programs to pyramid resistance genes in desirable wheat genotypes. This approach aims to combine agricultural traits, yield, and other physiological characteristics to produce cultivars with stable resistance, which would be better equipped to combat brown rust. [ABSTRACT FROM AUTHOR]

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Aim. To study resistance to leaf, yellow and stem rusts of winter and spring wheat and winter triticale samples from the collection of the N. I. Vavilov All‐Russian Institute of Plant Genetic Resources (VIR) and breeding centres of southern Russia in different phases of ontogenesis and to identify new sources with group resistance. Material and Methods. The resistance of 158 wheat and triticale samples from the VIR collection and southern breeding centres to populations of leaf, stem and yellow rusts in different plant growth stages was analysed. In the juvenile phase the samples studied were inoculated with populations of rust fungi in climate chambers of the Federal Research Centre of Biological Plant Protection and the type of plant reaction to lesions was noted. In field conditions the samples were evaluated according to the CIMMYT scale on an artificial infectious background. Results. In the adult plant stage under field conditions 79 wheat and triticale samples with group resistance to leaf, yellow and stem rusts were identified, and in the juvenile stage 26 samples. 22 samples showed resistance to three rusts in both phases of ontogenesis. Of these, 5 samples belong to the VIR collection, 3 winter triticale varieties (Dozor, Knyaz, Svat) and the Kavalerka wheat variety selection of the P.P. Lukyanenko National Grain Centre, 9 lines from the Donskoy Agrarian Research Centre and the Federal Rostov Agrarian Research Centre, and 4 winter triticale varieties (Ataman Platov, Zimogor, Kapral, Legion) of selections of the Federal Rostov Agrarian Research Centre. Conclusion. The samples of wheat and winter triticale with group resistance which have been identified are promising for use in breeding for immunity to rust diseases.

Wheat leaf rust, caused by Puccinia triticina, poses a growing threat to global wheat production, necessitating alternative strategies for effective disease management. This study investigated the potential of gamma-aminobutyric acid (GABA) to enhance resistance to leaf rust in two wheat cultivars: the susceptible Morocco and moderately resistant Sakha 94 cultivar. Our findings revealed that GABA significantly improved resistance in both cultivars to P. triticina, particularly in Morocco, by mitigating disease severity and reducing pustule density and size while extending both incubation and latent periods. This study assessed the effectiveness of two GABA application methods: plants received 1 mM GABA treatment, as a foliar spray, twenty-four hours prior to infection (pre-GABA), and plants received 1 mM GABA treatment both 24 h before and after infection (pre-/post-GABA), with the latter yielding significantly better results in reducing infection severity and improving plant resilience. Additionally, GABA application influenced stomatal behavior, promoting closure that may enhance resilience against leaf rust. GABA application on plants also modulated the production of reactive oxygen species (ROS). This led to a stronger oxidative burst in both susceptible and moderately resistant cultivars. GABA increased O2●− levels in guard cells and surrounding stomata, enhancing stomatal closure and the hypersensitive response. GABA enhanced the accumulation of soluble phenols and increased the activity of key antioxidant enzymes, catalase (CAT) and peroxidase (POX), which are vital for managing oxidative stress. To the best of our knowledge, this investigation represents the first report into the impact of GABA on wheat leaf rust disease.

Leaf rust on wheat caused by P. triticina is the most widespread fungal disease worldwide and in Bulgaria. The development of wheat genotypes resistant to leaf rust is related to the different types of resistance and ways of gene inheritance. The different varieties have different susceptibility during the different stages of their ontogenetic development. The study of the initial material is an important step in the breeding for resistance and it is an ongoing process. Two hundred and forty-six breeding lines were tested against the local population of P. triticina during 2015-2017, under conditions of infection field and in a greenhouse at Dobrudzha Agricultural Institute -- General Toshevo, Bulgaria. Twenty lines were selected, which demonstrated different degrees of resistance under infection field conditions and which showed resistance to some of the seven pathotypes used in the study. The identification of the pathotypes was based on the type of reaction of 20 monogenic lines. The reaction of isogenic lines was compared with the reaction of the selection lines and the results showed that the reaction of line 165/05-46 corresponded to isogenic lines carrying genes Lr 9, Lr 19 and Lr 25. The response of the other 3 lines (245/03-72, 13/04-97, 14/06-110) partially coincided with the response of the above mentioned genes. The reaction of the other 3 lines (169/05-69, 14/06-81, 8/08-25) partially coincided with the reaction of isogenic lines carrying genes Lr 2a, Lr 28 and Lr 29. It was determined that seven of the lines were carriers of a race-specific gene and that it was necessary to subject these lines to further breeding and genetic studies to determine presence of race-specific resistance. Five of the lines (72/05-53, 61/03-75, 106/04-189, 268/03-151, 79/04-131) combined incomplete resistance at young stage with resistance at adult stage. Four of the tested lines (68/06-78, 29/02-133-38, 79/04-125-28, 197/05-33) exhibited typical race non-specific resistance or APR. Four lines (13/04-165, 14/05-119, 19/06-79 and 61/03-81) demonstrated "slow rusting" type of resistance. Twenty of the studied lines were carriers of effective resistance and can be included in the breeding programs as donors of resistance to P. triticina. [ABSTRACT FROM AUTHOR]

Wheat leaf rust, caused by Puccinia triticina, is reported annually in southern Russia, the main wheat production region in Russia. The effect of biotic (types of cultivar resistance) and abiotic (northern, central and southern agro‐ecological zones) factors on virulence variability of the pathogen was analysed with 43 Lr differentials. Virulence frequencies to Lr genes 1, 2c, 3, 3bg, 11, 14a, 14b, 16, 17, 18, 23, 25, 26, 33, 34, 40 and Kanr exceeded 50% in all populations. A total of 81 virulence phenotypes (based on the standard set of 20 differentials) were identified among 108 isolates. The most common phenotypes were PHSTQ, THTTR, PHTTR and TKTTR. The minimum genetic distance (the highest similarity) was established between the P. triticina populations from susceptible cv. Krasnodarskaya 99 and cv. Brigada with race‐specific resistance. P. triticina populations from the susceptible cultivar in the three agro‐ecological zones were less variable and more similar than the cultivar‐specific and natural pathogen populations. Resistance types of host cultivars seem to have a greater effect on the pathogen population than abiotic factors. Nevertheless, abiotic factors need to be considered when making decisions about deployment of wheat varieties. Our results support the paradigm of a shift in the population of an obligate parasite towards increased virulence in response to the selection pressure of cultivars with race‐specific resistance. [ABSTRACT FROM AUTHOR]

Puccinia triticina, the causal agent of wheat leaf rust, is a dynamic pathogen causing significant yield losses worldwide. In this study, we analysed the virulence and genetic structure of 98 P. triticina isolates collected in Canada between 2018 and 2020. Isolates from Manitoba and Saskatchewan were found to be highly related for virulence, as were isolates from Quebec and Ontario. Isolates from Alberta had a virulence profile more similar to those from Manitoba and Saskatchewan than to Ontario and Quebec. To study the genetic structure of P. triticina populations, we used the restriction site‐associated DNA (RAD) genotyping‐by‐sequencing method to identify single‐nucleotide polymorphisms (SNPs). The Puccinia DNA sequences were aligned against the reference genome of P. triticina race BBBD and 1898 SNPs were identified. The phylogenetic analysis using SNP markers grouped these P. triticina into three genetic clades. The separation of P. triticina into three genetic clades was also supported by principal component analysis. Isolates from Clade 1 and Clade 2 were found throughout Canada, whereas Clade 3 isolates were only found in Ontario and Quebec. There were differences in virulence profiles among P. triticina isolates from the three genetic clades and a general correlation between virulence phenotypes and SNP genotypes was observed. These results indicate that the SNPs derived from RAD genotyping‐by‐sequencing could be useful in tracking the genetic and virulence dynamics of this pathogen in Canadian wheat. [ABSTRACT FROM AUTHOR]

'MN‐Torgy' (Reg. no. CV‐1203, PI 698205) hard red spring wheat (Triticum aestivium L.) was released by the University of Minnesota Agricultural Experiment Station in 2020 because of its high grain yield, disease resistance, and end‐use quality characteristics. MN‐Torgy is a medium‐maturity cultivar with above average plant height despite containing the semi‐dwarfing allele Rht24b. MN‐Torgy has moderate resistance to Fusarium head blight (caused primarily by Fusarium graminearum Schwabe) and good resistance to prevalent races of pathogens causing leaf rust (Puccinia triticina Eriks.) and stem rust (Puccinia graminis Pers.:Pers. f. sp. tritici Eriks. & E. Henn.) and is well adapted to the north‐central United States. MN‐Torgy also has good adult plant resistance to the Ug99 family of stem rust races. Core Ideas: MN‐Torgy is a new hard red spring wheat cultivar.MN‐Torgy spring wheat has field resistance to the Ug99 family of stem rust races.MN‐Torgy spring wheat is moderately resistant to Fusarium head blight. [ABSTRACT FROM AUTHOR]

Puccinia triticina (Pt), as the causal agent of wheat leaf rust, employs a plethora of effector proteins to modulate wheat immunity for successful colonization. Understanding the molecular mechanisms underlying Pt effector-mediated wheat susceptibility remains largely unexplored. In this study, an effector Pt_21 was identified to interact with the apoplast-localized wheat thaumatin-like protein TaTLP1 using a yeast two-hybrid assay and the Pt_21-TaTLP1 interaction was characterized. The interaction between Pt_21 and TaTLP1 was validated by in vivo co-immunoprecipitation assay. A TaTLP1 variant, TaTLP1C71A, that was identified by the site-directed mutagenesis failed to interact with Pt_21. Pt_21 was able to suppress Bax-mediated cell death in leaves of Nicotiana benthamiana and inhibit TaTLP1-mediated antifungal activity. Furthermore, infiltration of recombinant protein Pt_21 into leaves of transgenic wheat line overexpressing TaTLP1 enhanced the disease development of leaf rust compared to that in wild-type leaves. These findings demonstrate that Pt_21 suppresses host defense response by directly targeting wheat TaTLP1 and inhibiting its antifungal activity, which broadens our understanding of the molecular mechanisms underlying Pt effector-mediated susceptibility in wheat.

Leaf rust (Puccinia triticina) is a common disease that causes significant yield losses in wheat. The most frequently used methods to control leaf rust are the application of fungicides and the cultivation of resistant genotypes. However, high genetic diversity and associated adaptability of pathogen populations hamper achieving durable resistance in wheat. Emerging alternatives, such as microbial priming, may represent an effective measure to stimulate plant defense mechanisms and could serve as a means of controlling a broad range of pathogens. In this study, 175 wheat genotypes were inoculated with two bacterial strains: Ensifer meliloti strain expR+ch (producing N-acyl homoserine lactone (AHL)) or transformed E. meliloti carrying the lactonase gene attM (control). In total, 21 genotypes indicated higher resistance upon bacterial AHL priming. Subsequently, the phenotypic data of 175 genotypes combined with 9917 single-nucleotide polymorphisms (SNPs) in a genome-wide association study to identify quantitative trait loci (QTLs) and associated markers for relative infection under attM and expR+ch conditions and priming efficiency using the Genome Association and Prediction Integrated Tool (GAPIT). In total, 15 QTLs for relative infection under both conditions and priming efficiency were identified on chromosomes 1A, 1B, 2A, 3A, 3B, 3D, 6A, and 6B, which may represent targets for wheat breeding for priming and leaf-rust resistance.

Spring bread wheat (Triticum aestivum) is a major crop in Russia and in Kazakhstan. The rust pathogens, leaf rust caused by the fungus Puccinia triticina, stem rust incited by P. graminis and yellow rust caused by P. striiformis, are the significant biotic factors affecting wheat production. In this study, 40 new promising spring wheat genotypes from the Kazakhstan-Siberia Network for Spring Wheat Improvement (KASIB) were tested for resistance to leaf, stem and yellow rust at the seedling stage, and for identification of rust resistance genes using molecular markers. In addition, the collection was tested for leaf rust resistance and grain yields in the South Urals agroclimatic zone of Russia in 2023. As a result, 16 accessions with seedling resistance to leaf rust, 21 to stem rust and 4 to yellow rust were identified. Three breeding accessions were resistant to all rust species, and nine to P. triticina and P. graminis. Wheat accessions resistant to leaf rust at the seedling stage were also resistant in the field. Molecular analysis showed the presence of cataloged resistance genes, Lr1, Lr3a, Lr9, Lr10, Lr19, Lr20, Lr24, Lr26, Sr15, Sr24, Sr25, Sr31, Sr38, Yr9 and Yr18; uncatalogued genes Lr6Agi1 and Lr6Agi2 from Thinopyrum intermedium and LrAsp from Aegilops speltoides; and 1AL.1RS translocation. The current analysis showed an increase in leaf and stem rust resistance of new KASIB genotypes and their genetic diversity due to the inclusion of alien genetic material in breeding.

Wheat leaf rust, caused by Puccinia triticina, is one of the most common fungal diseases of wheat in China and occurs widely in various wheat-growing regions. To clarify the epidemic, spread rules, and population structure of P. triticina among different regions, 217 isolates of P. triticina collected from Hebei, Shandong, Sichuan, and Xinjiang in China were tested by 34 Thatcher near-isogenic lines and 21 pairs of EST-SSR primers. A total of 83 races were identified, and THTT, PHTT, THTS, and PHJT were the most predominant races in the four provinces in 2009. We found enriched virulence and genetic diversity in the four P. triticina populations and a significant correlation between genetic polymorphism and geographic regions. However, no significant correlation was found between virulence phenotypes and molecular genotypes. Moreover, a notable high level of gene flow (Nm = 2.82 > 1) among four P. triticina populations was detected. The genetic relationship among Hebei, Shandong, and Sichuan populations was close, possibly due to the spread of P. triticina from Sichuan to Shandong and then to Hebei. In contrast, the Xinjiang population was relatively independent. Genetic differentiation analysis showed some level of differentiation among or within populations of P. triticina in the four provinces, and the genetic variation within populations (74.97%) was higher than across populations (25.03%). Our study provides a basis for a better understanding of the regional migration, epidemic, and population structure of P. triticina in China.

Effectors are considered to be virulence factors secreted by pathogens, which play an important role during host-pathogen interactions. In this study, the candidate effector Pt9226 was cloned from genomic DNA of Puccinia triticina (Pt) pathotype THTT, and there were six exons and five introns in the 877 bp sequence, with the corresponding open reading frame of 447 bp in length, encoding a protein of 148 amino acids. There was only one polymorphic locus of I142V among the six Pt pathotypes analyzed. Bioinformatics analysis showed that Pt9226 had 96.46% homology with the hypothetical putative protein PTTG_26361 (OAV96349.1) in the Pt pathotype BBBD. RT-qPCR analyses showed that the expression of Pt9226 was induced after Pt inoculation, with a peak at 36 hpi, which was 20 times higher than the initial expression at 0 hpi, and another high expression was observed at 96 hpi. No secretory function was detected for the Pt9226-predicted signal peptide. The subcellular localization of Pt9226Δsp-GFP was found to be multiple, localized in the tobacco leaves. Pt9226 could inhibit programmed cell death (PCD) induced by BAX/INF1 in tobacco as well as DC3000-induced PCD in wheat. The transient expression of Pt9226 in 26 wheat near-isogenic lines (NILs) by a bacterial type III secretion system of Pseudomonas fluorescens EtHAn suppressed callose accumulation triggered by Ethan in wheat near-isogenic lines TcLr15, TcLr25, and TcLr30, and it also suppressed the ROS accumulation in TcLr15. RT-qPCR analysis showed that the expression of genes coded for pathogenesis-related protein TaPR1, TaPR2, and thaumatin-like protein TaTLP1, were suppressed, while the expression of PtEF-1α was induced, with 1.6 times at 72 h post inoculation, and TaSOD was induced only at 24 and 48 h compared with the control, when the Pt pathotype THTT was inoculated on a transient expression of Pt9226 in wheat TcLr15. Combining all above, Pt9226 acts as a virulence effector in the interaction between the Pt pathotype THTT and wheat.

Wheat leaf rust fungus is an obligate parasitic fungus that can absorb nutrients from its host plant through haustoria and secrete effector proteins into host cells. The effector proteins are crucial factors for pathogenesis as well as targets for host disease resistance protein recognition. Exploring the role of effector proteins in the pathogenic process of Puccinia triticina Eriks. (Pt) is of great significance for unraveling its pathogenic mechanisms. We previously found that a cysteine-rich effector protein, Pt1641, is highly expressed during the interaction between wheat and Pt, but its specific role in pathogenesis remains unclear. Therefore, this study employed techniques such as heterologous expression, qRT-PCR analysis, and host-induced gene silencing (HIGS) to investigate the role of Pt1641 in the pathogenic process of Pt. The results indicate that Pt1641 is an effector protein with a secretory function and can inhibit BAX-induced programmed cell death in Nicotiana benthamiana. qRT-PCR analyses showed that expression levels of Pt1641 were different during the interaction between the high-virulence strain THTT and low-virulence strains FGD and Thatcher, respectively. The highest expression level in the low-virulence strain FGD was four times that of the high-virulence strain THTT. The overexpression of Pt1641 in wheat near-isogenic line TcLr1 induced callose deposition and H2O2 production on TcLr1. After silencing Pt1641 in the Pt low-virulence strain FGD on wheat near-isogenic line TcLr1, the pathogenic phenotype of Pt physiological race FGD on TcLr1 changed from “;” to “3”, indicating that Pt1641 plays a non-toxic function in the pathogenicity of FGD to TcLr1. This study helps to reveal the pathogenic mechanism of wheat leaf rust and provides important guidance for the mining and application of Pt avirulent genes.

The response of 250 common winter wheat breeding lines was investigated for resistance to the causative agent of Puccinia triticina under conditions of an infected field on the territory of Dobrudzha Agricultural Institute – General Toshevo, Bulgaria, during three successive seasons. Twenty lines with different degrees of resistance under field conditions were selected. Multi-pathotype testing was used to study the response of these lines at seedling stage under greenhouse conditions to individual pathotypes of P. triticina. Based on the response of the lines at seedling and adult stages, we found out that 20 % of them carried race-specific resistance. One of the lines (99/08-52) reacted with full resistance to the pathotypes used under greenhouse conditions. The reaction demonstrated by this line coincided with the response of isogenic lines carrying the genes Lr9, Lr19, Lr22a, Lr22b and Lr25. The other three lines (19/06-108, 82/08-43 and 82/08-35) showed a resistant reaction to 6 or 5 of the pathotypes used in the study. Their response partially coincided with the reaction of 5 isogenic lines, and the presence of some of these genes in the above lines is quite possible. Lines carrying this type of resistance are to be subjected to further genetic and breeding investigations to prove the presence of a race-specific gene. Twenty-five percent of the lines combined partial race-specific resistance at seedling stage with the resistance of race non-specific nature at adult stage. Forty percent of all studied lines carried race non-specific resistance, and 15 % of the lines possessed resistance of the “slow rusting” type. As a result of the study we carried out, the lines that demonstrated stable resistance to leaf rust can provide sufficient protection of the host and can be included in the breeding programs for developing varieties resistant to P. triticina.

Wheat leaf rust is a devastating disease worldwide. Identification of leaf rust resistance genes in seedlings and of genes for slow rusting are important in resistance breeding and for gene deployment to control the disease. A total of 108 wheat cultivars from the Beijing and Shandong province and a set of 36 differentials, mostly near-isogenic lines in the background of Thatcher with known leaf rust resistance genes, were tested with 20 Puccinia triticina pathotypes (FHJS1, FGBQ,PGJQ, SHJT, FHGQ, PHTT1, FHGQ, FHGQ, PHJS, THSM, FHSQ, PHST, PRSQ, FNTQ, PHGM, KHGQ, PHTT2, TGTT, FHJS2, NHHT) at the seedling stage in the greenhouse. The cultivars and differentials were also planted in the field to test their slow rusting resistance using a mixture of races at Baoding, Hebei province and Zhoukou, Henan province, for two consecutive years. Ten leaf rust resistance genes, Lr1, 9, 10, 19, 20, 24, 26, 34, 37 and 46 were identified in the 57 commercial wheat cultivars, either singly or in combination, using molecular markers. Combined, the results from gene postulation and marker detection showed that one or more of the genes Lr1, 3, 10, 14a, 14b, 26, 36, 39, 34 and 46, were present in 57 cultivars, and that no known resistance gene was present in the remaining 51 cultivars. The resistance gene Lr26 was present in 42 cultivars, and nine cultivars contained Lr1. Lr46 was present in 10 cultivars, as indicated by the presence of the closely linked marker csLV46G22. Seven genotypes were identified as possibly carrying the gene Lr39. Lr3 and 10 were found in six and four genotypes, respectively. The ggenes Lr14b and 34 were each present in three cultivars, while evidence for the presence of Lr14a and 36 was obtained in single genotypes. Finally, 12 cultivars showed slow rusting resistance at two locations in two crop seasons. The identification of leaf rust resistance genes in Chinese wheat cultivars will be helpful for gene deployment to control leaf rust.

Background: Screening and developing novel antifungal agents with minimal environmental impact are needed to maintain and increase crop production, which is constantly threatened by various pathogens. Small peptides with antimicrobial and antifungal activities have been known to play an important role in plant defense both at the pathogen level by suppressing its growth and proliferation as well as at the host level through activation or priming of the plant’s immune system for a faster, more robust response against fungi. Rust fungi (Pucciniales) are plant pathogens that can infect key crops and overcome resistance genes introduced in elite wheat cultivars. Results: We performed an in vitro screening of 18 peptides predominantly of plant origin with antifungal or antimicrobial activity for their ability to inhibit leaf rust (Puccinia triticina, CCDS-96-14-1 isolate) urediniospore germination. Nine peptides demonstrated significant fungicidal properties compared to the control. Foliar application of the top three candidates, β-purothionin, Purothionin-α2 and Defensin-2, decreased the severity of leaf rust infection in wheat (Triticum aestivum L.) seedlings. Additionally, increased pathogen resistance was paralleled by elevated expression of defense-related genes. Conclusions: Identified antifungal peptides could potentially be engineered in the wheat genome to provide an alternative source of genetic resistance to leaf rust.

Wheat leaf rust, caused by the obligate biotrophic fungus Puccinia triticina Eriks. (Pt), is one of the most common wheat foliar diseases that continuously threatens global wheat production. Currently, the approaches used to mitigate pathogen infestation include the application of fungicides and the deployment of resistance genes or cultivars. However, the continuous deployment of selected resistant varieties causes host selection pressures that drive Pt evolution and promote the incessant emergence of new virulent races, resulting in the demise of wheat-resistant cultivars after several years of planting. Intriguingly, diploid wheat accessions were found to confer haustorium formation-based resistance to leaf rust, which involves prehaustorial and posthaustorial resistance mechanisms. The prehaustorial resistance in the interaction between einkorn and wheat leaf rust is not influenced by specific races of the pathogen. The induced defense mechanism, known as systemic acquired resistance, also confers durable resistance against a wide array of pathogens. This review summarizes the host range, pathogenic profile, and evolutionary basis of Pt; the molecular basis underlying wheat–Pt interactions; the cloning and characterization of wheat leaf rust resistance genes; prehaustorial and posthaustorial resistance; systemic acquired resistance; and the role of reactive oxygen species. The interplay between climatic factors, genetic features, planting dates, and disease dynamics in imparting resistance is also discussed. [ABSTRACT FROM AUTHOR]