Inactivation of a wheat protein kinase gene confers broad-spectrum resistance to rust fungi.

Wheat crops are frequently devastated by pandemic stripe rust caused by Puccinia striiformis f. sp. tritici (Pst). Here, we identify and characterize a wheat receptor-like cytoplasmic kinase gene, TaPsIPK1, that confers susceptibility to this pathogen. PsSpg1, a secreted fungal effector vital for Pst virulence, can bind TaPsIPK1, enhance its kinase activity, and promote its nuclear localization, where it phosphorylates the transcription factor TaCBF1d for gene regulation. The phosphorylation of TaCBF1d switches its transcriptional activity on the downstream genes. CRISPR-Cas9 inactivation of TaPsIPK1 in wheat confers broad-spectrum resistance against Pst without impacting important agronomic traits in two years of field tests. The disruption of TaPsIPK1 leads to immune priming without constitutive activation of defense responses. Taken together, TaPsIPK1 is a susceptibility gene known to be targeted by rust effectors, and it has great potential for developing durable resistance against rust by genetic modifications.

Integrated genome-wide association and transcriptomic analysis to identify receptor kinase genes to stripe rust resistance in wheat germplasm from southwestern China.

Stripe rust of wheat, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most important diseases of wheat worldwide. Identification of new and elite Pst-resistance loci or genes has the potential to enhance overall resistance to this pathogen. Here, we conducted an integrated genome-wide association study (GWAS) and transcriptomic analysis to screen for loci associated with resistance to stripe rust in 335 accessions from Yunnan, including 311 landraces and 24 cultivars. Based on the environmental phenotype, we identified 113 protein kinases significantly associated with Pst resistance using mixed linear model (MLM) and generalized linear model (GLM) models. Transcriptomic analysis revealed that 52 of 113 protein kinases identified by GWAS were up and down regulated in response to Pst infection. Among these genes, a total of 15 receptor kinase genes were identified associated with Pst resistance. 11 candidate genes were newly discovered in Yunnan wheat germplasm. Our results revealed that resistance alleles to stripe rust were accumulated in Yunnan wheat germplasm, implying direct or indirect selection for improving stripe rust resistance in elite wheat breeding programs.

Genome-wide association study identifies novel loci and candidate genes for rust resistance in wheat (Triticum aestivum L.).

BACKGROUND: Wheat rusts are important biotic stresses, development of rust resistant cultivars through molecular approaches is both economical and sustainable. Extensive phenotyping of large mapping populations under diverse production conditions and high-density genotyping would be the ideal strategy to identify major genomic regions for rust resistance in wheat. The genome-wide association study (GWAS) population of 280 genotypes was genotyped using a 35 K Axiom single nucleotide polymorphism (SNP) array and phenotyped at eight, 10, and, 10 environments, respectively for stem/black rust (SR), stripe/yellow rust (YR), and leaf/brown rust (LR). RESULTS: Forty-one Bonferroni corrected marker-trait associations (MTAs) were identified, including 17 for SR and 24 for YR. Ten stable MTAs and their best combinations were also identified. For YR, AX-94990952 on 1A + AX-95203560 on 4A + AX-94723806 on 3D + AX-95172478 on 1A showed the best combination with an average co-efficient of infection (ACI) score of 1.36. Similarly, for SR, AX-94883961 on 7B + AX-94843704 on 1B and AX-94883961 on 7B + AX-94580041 on 3D + AX-94843704 on 1B showed the best combination with an ACI score of around 9.0. The genotype PBW827 have the best MTA combinations for both YR and SR resistance. In silico study identifies key prospective candidate genes that are located within MTA regions. Further, the expression analysis revealed that 18 transcripts were upregulated to the tune of more than 1.5 folds including 19.36 folds (TraesCS3D02G519600) and 7.23 folds (TraesCS2D02G038900) under stress conditions compared to the control conditions. Furthermore, highly expressed genes in silico under stress conditions were analyzed to find out the potential links to the rust phenotype, and all four genes were found to be associated with the rust phenotype. CONCLUSION: The identified novel MTAs, particularly stable and highly expressed MTAs are valuable for further validation and subsequent application in wheat rust resistance breeding. The genotypes with favorable MTA combinations can be used as prospective donors to develop elite cultivars with YR and SR resistance.

Evaluation of effectiveness resistance genes in wheat genotypes using marker-assisted selection for stripe rust resistance breeding".

Stripe rust, induced by Puccinia striiformis f. sp. tritici, is the most harmful and prevalent disease in temperate regions worldwide, affecting wheat production areas globally. An effective strategy for controlling the disease involves enhancing genetic resistance against stripe rust, achieved through Egyptian breeding efforts not previously conducted on wheat genotypes. The resistance level to stripe rust in thirty-eight wheat genotypes was assessed using marker-assisted selection methods. The investigation suggests that wheat breeding programs can utilize slow-rusting Yr genes, which are effective resistance genes, to develop novel genotypes with stripe rust resistance through marker-assisted breeding. Based on the four disease responses of the wheat genotypes under investigation, the results categorized the genotypes into three groups. The first group included resistant genotypes, the second group exhibited a slow-rusting character with the lowest disease symptom rates, and the last group displayed the highest disease characteristics rates throughout the three seasons, comprising fast-rusting genotypes. The rust-resistant genes identified were Yr5, Yr9, Yr10, Yr15, Yr17, Yr18, Yr26, Yr29, Yr30, and Yr36. Genes Yr26, Yr30, and Yr36 were present in all genotypes. Genotypes Misr3, Misr4, Giza168, Giza167, Giza170, Giza171, Gemmeiza9, and Gemmeiza10 carried the Yr9 gene. Only one genotype, Sids13, was found to have the Yr17 gene. Genes Yr18 and Yr29 were identified in Sids14, Giza168, Giza170, Gemmeiza9, and Gemmeiza10. However, none of the wheat genotypes showed the presence of Yr5, Yr10, or Yr15. Several backcrossing generations were conducted to introduce the Yr5 and Yr10 genes into susceptible genotypes (Misr1, Misr2, and Gemmeiza11). These genotypes are cultivated globally and are known for producing high-quality flour, making them of great importance to farmers. The study demonstrates significant potential for enhancing wheat genotypes for stripe rust resistance and increased production.

Co-expression network analysis and identification of core genes in the interaction between wheat and Puccinia striiformis f. sp. tritici.

The epidemic of stripe rust, caused by the pathogen Puccinia striiformis f. sp. tritici (Pst), would reduce wheat (Triticum aestivum) yields seriously. Traditional experimental methods are difficult to discover the interaction between wheat and Pst. Multi-omics data analysis provides a new idea for efficiently mining the interactions between host and pathogen. We used 140 wheat-Pst RNA-Seq data to screen for differentially expressed genes (DEGs) between low susceptibility and high susceptibility samples, and carried out Gene Ontology (GO) enrichment analysis. Based on this, we constructed a gene co-expression network, identified the core genes and interacted gene pairs from the conservative modules. Finally, we checked the distribution of Nucleotide-binding and leucine-rich repeat (NLR) genes in the co-expression network and drew the wheat NLR gene co-expression network. In order to provide accessible information for related researchers, we built a web-based visualization platform to display the data. Based on the analysis, we found that resistance-related genes such as TaPR1, TaWRKY18 and HSP70 were highly expressed in the network. They were likely to be involved in the biological processes of Pst infecting wheat. This study can assist scholars in conducting studies on the pathogenesis and help to advance the investigation of wheat-Pst interaction patterns.

Introgression of tetraploid Thinopyrum elongatum 6EL segments enhances the stripe rust resistance of adult wheat plants.

Preventing the widespread occurrence of stripe rust in wheat largely depends on the identification of new stripe rust resistance genes and the breeding of cultivars with durable resistance. In previous study, we reported 6E of wheat-tetraploid Thinopyrum elongatum 6E (6D) substitution line contains adult-stage stripe rust resistance genes. In this study, three novel wheat-tetraploid Th. elongatum translocation lines were generated from the offspring of a cross between common wheat and the 6E (6D) substitution line. Genomic in situ hybridization (GISH), fluorescence in situ hybridization chromosome painting (FISH painting), repetitive sequential FISH, and 55 K SNP analyses indicated that K227-48, K242-82, and K246-6 contained 42 chromosomes and were 6DL·6ES, 2DL·6EL, and 6DS·6EL translocation lines, respectively. The assessment of stripe rust resistance revealed that K227-48 was susceptible to a mixture of Pst races, whereas the 6EL lines K242-82 and K246-6 were highly resistance to stripe rust at the adult stage. Thus, this resistance was due to the chromosome arm 6EL of tetraploid Th. elongatum. The improved agronomic performance of 6DS·6EL translocation line may be a useful novel germplasm resource for wheat breeding programs. For the application of marker-assisted selection (MAS), 47 simple sequence repeat (SSR) markers were developed, showing specific amplification on the chromosome 6E using the whole-genome sequence of diploid Th. elongatum. The 6DS·6EL translocation line and SSR markers have the potential to be deploy for future stripe rust resistance wheat breeding program. Supplementary Information: The online version contains supplementary material available at 10.1007/s11032-024-01493-6.

Genetic dissection and identification of stripe rust resistance genes in the wheat cultivar Lanhangxuan 121, a cultivar selected from a space mutation population.

Stripe rust is a devastating disease of wheat worldwide. Chinese wheat cultivar Lanhangxuan 121 (LHX121), selected from an advanced line L92-47 population that had been subjected to space mutation breeding displayed a consistently higher level of resistance to stipe rust than its parent in multiple field environments. The aim of this research was to establish the number and types of resistance genes in parental lines L92-47 and LHX121 using separate segregating populations. The first population developed from a cross between LHX121 and susceptible cultivar Xinong 822 comprised 278 F2:3 lines. The second validation population comprised 301 F2:3 lines from a cross between L92-47 and susceptible cultivar Xinong 979. Lines of two population were evaluated for stripe rust response at three sites during the 2018-2020 cropping season. Affymetrix 660 K SNP arrays were used to genotype the lines and parents. Inclusive composite interval mapping detected QTL QYrLHX.nwafu-2BS, QYrLHX.nwafu-3BS, and QYrLHX.nwafu-5BS for resistance in all three environments. Based on previous studies and pedigree information, QYrLHX.nwafu-2BS and QYrLHX.nwafu-3BS were likely to be Yr27 and Yr30 that are present in the L92-47 parent. QYrLHX.nwafu-5BS (YrL121) detected only in LHX121 was mapped to a 7.60 cM interval and explained 10.67-22.57% of the phenotypic variation. Compared to stripe rust resistance genes previously mapped to chromosome 5B, YrL121 might be a new adult plant resistance QTL. Furthermore, there were a number of variations signals using 35 K SNP array and differentially expressed genes using RNA-seq between L92-47 and LHX121 in the YrL121 region, indicating that they probably impair the presence and/or function of YrL121. Supplementary Information: The online version contains supplementary material available at 10.1007/s11032-024-01461-0.

Inoculum Sources of Puccinia striiformis f. sp. tritici for Stripe Rust Epidemics on the Eastern Coast of China.

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 phenotyping, 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.

Genetic Diversity and Population Structure of Wheat Stripe Rust Pathogen (Puccinia striiformis f. sp. tritici) in Turkey.

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.

Identification of adult resistant genes to stripe rust in wheat from southwestern China based on GWAS and WGCNA analysis.

KEY MESSAGE: In this study, genome-wide association studies combined with transcriptome data analysis were utilized to reveal potential candidate genes for stripe rust resistance in wheat, providing a basis for screening wheat varieties for stripe rust resistance. Wheat stripe rust, which is caused by the wheat stripe rust fungus (Puccinia striiformis f. sp. tritici, Pst) is one of the world's most devastating diseases of wheat. Genetic resistance is the most effective strategy for controlling diseases. Although wheat stripe rust resistance genes have been identified to date, only a few of them confer strong and broad-spectrum resistance. Here, the resistance of 335 wheat germplasm resources (mainly wheat landraces) from southwestern China to wheat stripe rust was evaluated at the adult stage. Combined genome-wide association study (GWAS) and weighted gene co-expression network analysis (WGCNA) based on RNA sequencing from stripe rust resistant accession Y0337 and susceptible accession Y0402, five candidate resistance genes to wheat stripe rust (TraesCS1B02G170200, TraesCS2D02G181000, TraesCS4B02G117200, TraesCS6A02G189300, and TraesCS3A02G122300) were identified. The transcription level analyses showed that these five genes were significantly differentially expressed between resistant and susceptible accessions post inoculation with Pst at different times. These candidate genes could be experimentally transformed to validate and manipulate fungal resistance, which is beneficial for the development of the wheat cultivars resistant to stripe rust.

Uncovering the history of recombination and population structure in western Canadian stripe rust populations through mating type alleles.

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.

New Races with Wider Virulence Indicate Rapid Evolution of Puccinia striiformis f. sp. tritici in the Southern Cone of America.

Wheat yellow (stripe) rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most devastating diseases of wheat worldwide. Pst populations are composed of multiple genetic groups, each carrying one or more races characterized by different avirulence/virulence combinations. Since the severe epidemics in 2017, yellow rust has become the most economically important wheat foliar disease in Uruguay. A set of 124 Pst isolates collected from wheat fields in Uruguay between 2017 and 2021 were characterized phenotypically, and 27 of those isolates were subsequently investigated in-depth by additional molecular genotyping and race phenotyping analyses. Three genetic groups were identified, PstS7, PstS10, and PstS13, with the latter being the most prevalent. Two races previously reported in Europe, Warrior (PstS7) and Benchmark (PstS10), were detected in four and two isolates, respectively. A third race, known as Triticale2015 (PstS13), that was first detected in Europe in 2015 and in Argentina in 2017 was detected at several locations. Additional virulence to Yr3, Yr17, Yr25, Yr27, or Yr32 was detected in three new race variants within PstS13. The identification of these new races, which have not been reported outside South America, provides strong evidence of the local evolution of virulence in Pst during the recent epidemic years.

Virulence Characterization of Puccinia striiformis f. sp. tritici in China Using the Chinese and Yr Single-Gene Differentials.

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most important diseases of wheat. Identifying Pst races is essential for developing resistant cultivars and managing the disease. In this study, 608 isolates collected from China in 2021 were tested with the Chinese set of 19 wheat variety differentials and the set of 18 Yr single-gene differentials. Of the 119 races detected with the Chinese set of differentials, 94 were new. A higher number (149) of races were identified using the Yr single-gene differentials. The frequencies of virulence factors to 17 of the 19 Chinese differential varieties and to 10 of the 18 Yr single-gene differentials were high (>60%). None of the isolates were virulent to the differentials Zhong 4 (Yr genes unknown) and Triticum spelta Album (Yr5) in the Chinese set and the Yr5 and Yr15 lines in the single-gene set of differentials, indicating that these genes or varieties are effective against the Pst population detected in 2021. Using Nei's genetic distance, the 16 provincial Pst populations were clustered into six groups based on the Chinese set and eight groups based on the Yr single-gene set of differentials. In addition, we found that the same races identified using the Chinese differentials could be further differentiated into different races using the Yr single-gene differentials, suggesting a higher differential capability than the Chinese set of differentials. The results provide a scientific basis for monitoring Pst populations and guiding resistance breeding in China.

Favorable Loci Identified for Stripe Rust Resistance in Chinese Winter Wheat Accessions via Genome-Wide Association Study.

Stripe rust (or yellow rust), caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most devastating diseases of wheat worldwide. Currently, the utilization of resistant cultivars is the most viable way to reduce yield losses. In this study, a panel of 188 wheat accessions from China was evaluated for stripe rust resistance, and genome-wide association studies were performed using high-quality Diversity Arrays Technology markers. According to the phenotype and genotype data, a total of 26 significant marker-trait associations were identified, representing 18 quantitative trait loci (QTLs) on chromosomes 1B, 2A, 2B, 3A, 3B, 5A, 5B, 6B, 7B, and 7D. Of the 18 QTLs, almost all were associated with adult plant resistance (APR) except QYr.nwsuaf-6B.2, which was associated with all-stage resistance (also known as seedling resistance). Three of the 18 QTLs were mapped far from previously identified Pst resistance genes and QTLs and were considered potentially new loci. The other 15 QTLs were mapped close to known resistance genes and QTLs. Subsequent haplotype analysis for QYr.nwsuaf-2A and QYr.nwsuaf-7B.3 revealed the degrees of resistance of the panel in the APR stage. In summary, the favorable alleles identified in this study may be useful in breeding for disease resistance to stripe rust.

A Combination of Resistance Genes Confers High and Durable Resistance Against Stripe Rust in Wheat Cultivar Lantian 26.

'Lantian 26', a leading elite winter wheat cultivar in Gansu Province since its release in 2010, exhibits high resistance or immunization to stripe rust in the adult-plant stage under a high disease pressure in Longnan (southeastern Gansu). Identifying the resistance genes in 'Lantian 26' could provide a basis for enhanced durability and high levels of resistance in wheat cultivars. Here, a segregating population was developed from a cross between a highly susceptible wheat cultivar Mingxian 169 and the highly stripe rust-resistant 'Lantian 26'. The F2 and F2:3 progenies of the cross were inoculated with multiple prevalent virulent races of stripe rust for adult-plant-stage-resistance evaluation in two different environments. Exon sequence alignment analysis revealed that a stripe rust resistance gene on the 718.4- to 721.2-Mb region of chromosome 7BL, tentatively named as YrLT26, and a cosegregation sequence-tagged site (STS) marker GY17 was developed and validated using the F2:3 population and 103 wheat cultivars. The other two resistance genes, Yr9 and Yr30, were also identified in 'Lantian 26' using molecular markers. Therefore, the key to high and durable resistance to stripe rust at the adult stage is the combination of Yr9, Yr30, and YrLT26 genes in 'Lantian 26'. This could be a considerable strategy for improving the wheat cultivars with effective and durable resistance in the high-pressure region for stripe rust.

Evaluation of Stripe Rust Resistance and Chip Detection Resistance Genes in 286 Xinjiang Wheat Cultivars and Breeding Lines.

Wheat stripe rust is a destructive disease worldwide, caused by Puccinia striiformis f. sp. tritici (Pst). Resistance breeding is the most effective method of controlling stripe rust. Xinjiang is a relatively independent epidemic region of wheat stripe rust in China. In recent years, wheat stripe rust in this area has shown an upward trend. Therefore, the purpose of this study was to evaluate the resistance level of wheat cultivars (lines) to the prevalent Pst races and determine the genetic background of stripe rust resistance genes in Xinjiang. Six predominant Pst races in China were used to study resistance of 286 wheat cultivars (lines) at both seedling under controlled conditions and adult-plant stages under field conditions. In the seedling tests, 175 (61.19%) entries were resistant to races CYR23, 125 (43.71%) to CYR29, 153 (53.50%) to CYR31, 88 (30.77%) to CYR32, 174 (60.84%) to CYR33, and 98 (34.27%) to CYR34. Among the resistant entries, 23 (8.04%) were resistant to all six races. In the field test, 135 (47.20%) entries were resistant to the tested mixed races. Through comparing the responses in the seedling and adult-plant stages, 109 (38.11%) entries were found to have adult-plant resistance (APR), and 14 (4.90%) entries have all-stage resistance (ASR). The 286 wheat entries were also tested using a wheat breeder chip containing 12 Yr resistance loci. Among these entries, 44 (15.38%) were found to have single gene, 221 (77.27%) have two or more genes, and 21 (7.34%) have none of the 12 genes, including 144 (50.35%) with Yr30 and 5 (1.75%) with YrSP. Entries with two or more genes have stronger resistance to Pst. Overall, the majority of entries have all-stage and/or adult-plant resistance, but their genes for resistance in addition to the 12 tested Yr genes need to be determined. It is also necessary to introduce more effective resistance genes in the breeding programs to improve stripe rust resistance in wheat cultivars in Xinjiang.

Mapping of a Recessive Gene for All-Stage Resistance to Stripe Rust in a Wheat Line Derived from Cultivated Einkorn (Triticum monococcum).

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most destructive fungal diseases of wheat. Cultivated einkorn (Triticum monococcum L. ssp. monococcum, 2n = 2x = 14, AmAm), one of the founder crops of agriculture, harbors unexploited genetic sources for wheat improvement. An advanced wheat line, Z15-1949, with 42 chromosomes, selected from the hybrids of Pst-susceptible common wheat cultivar Crocus and resistant T. monococcum accession 10-1, exhibits high resistance to a mixture of the prevalent Chinese Pst races. Genetic analysis on F1, F2, and F2:3 generations of the cross between Z15-1949 and Pst-susceptible common wheat SY95-71 indicated that the resistance of Z15-1949 was conferred by a recessive gene, tentatively designated as YrZ15-1949. This gene was mapped to the short arm of chromosome 7D using the Wheat 55K single nucleotide polymorphism array, flanked by markers KASP-1949-2 and KASP-1949-10 within a 3.3-cM genetic interval corresponding to a 1.12-Mb physical region in the Chinese Spring reference genome V2.0. The gene differs from previously reported Yr genes on 7D based on their physical positions and is probably a novel gene. YrZ15-1949 would be a valuable resource for developing Pst-resistant wheat cultivars, and the linked markers could be used for marker-assisted selection.

Molecular genotyping analysis suggested high clonality and simple marker loci in Puccinia striiformis f. sp. tritici population in Uzbekistan, Central Asian region.

Puccinia striiformis f. sp. tritici (Pst) is a destructive pathogen that causes wheat stripe rust worldwide. Understanding the population structure and dynamic of pathogen spread is critical to fight against this disease. Limited information is available for the population genetic structure of Pst in Uzbekistan, Central Asia. In this study, we carried out surveillance from 9 different regions (Andijan, Fergana, Jizzakh, Kashkadarya, Namangan, Samarkand, Sirdaryo, Surkhandarya and Tashkent) of Uzbekistan to fill this gap. A total of 255 isolates were collected, which were genotyped using 17 polymorphic simple sequence repeats (SSR) markers. The DAPC analysis results showed no population subdivision in these sample-collected regions except Surkhandarya. Multilocus genotype (MLG) analysis, FST, and Nei's genetic distance results indicated a clonal population (rBarD ≤ 0.12) and merely three MLGs accounting for 70% of the overall population. MLG-34 was predominant in all Uzbekistan regions, followed by MLG-36 and MLG-42. Low genotypic diversity was observed in Andijan, Fergana, Jizzakh, Kashkadarya, Namangan, Sirdaryo, and Tashkent (0.56 to 0.76), compared with Samarkand (0.82) and Surkhandarya (0.97). No virulence against Yr5, Yr15, YrSp, and Yr26 was found, while resistant was overcome against Yr1, Yr2, Yr6, Yr9, Yr17, and Yr44 genes (Virulence frequency =≥75%). Comparative study results of Uzbekistan with previous Himalayan population were showed divergence from China and Pakistan populations. Further studies need to be conducted in a worldwide context to understand migration patterns; for that purpose, collaborative work is essential due to the Pst long-distance migration capability.

Cytogenetic and Genomic Characterization of a Novel Wheat-Tetraploid Thinopyrum elongatum 1BS⋠1EL Translocation Line with Stripe Rust Resistance.

Stripe rust, caused by Puccinia striiformis f. sp. tritici, is a destructive wheat disease pathogen. Thinopyrum elongatum is a valuable germplasm including diploid, tetraploid, and decaploid with plenty of biotic and abiotic resistance. In a previous study, we generated a stripe rust-resistant wheat-tetraploid Th. elongatum 1E/1D substitution line, K17-841-1. To further apply the wild germplasm for wheat breeding, we selected and obtained a new homozygous wheat-tetraploid Th. elongatum translocation line, T1BS⋅1EL, using genomic in situ hybridization, fluorescence in situ hybridization (FISH), oligo-FISH painting, and the wheat 55K single nucleotide polymorphism genotyping array. The T1BS⋅1EL is highly resistant to stripe rust at the seedling and adult stages. Pedigree and molecular marker analyses revealed that the resistance gene was located on the chromosome arm 1EL of tetraploid Th. elongatum, tentatively named Yr1EL. In addition, we developed and validated 32 simple sequence repeat markers and two kompetitive allele-specific PCR assays that were specific to the tetraploid Th. elongatum chromosome arm 1EL to facilitate marker-assisted selection for alien 1EL stripe rust resistance breeding. This will help us explore and locate the stripe rust resistance gene mapping on the 1E chromosome and deploy it in the wheat breeding program.

Wheat Stripe Rust Inoculum from the Southwest Dispersed to the East Huang-Huai-Hai Region through Southern Anhui in China.

Stripe rust, caused by Puccinia striiformis f. sp. tritici, is a continuous threat to global wheat production. In 2021, the epidemic of wheat stripe rust in China affected approximately 4.5 million hectares, resulting in severe yield losses. When confronted with the epidemic, tracing the sources of the pathogen can offer valuable insights for disease prevention and control. This study was conducted to analyze the genetic structure, aerodynamics, geographical features, and cultivation practices of the pathogen population in various wheat-producing regions, and to further reveal the spread patterns of the stripe rust pathogens in China. The findings indicated an overall trend of the pathogen dissemination from the west to the east. The pathogen was primarily spread from the northwestern region to the Huang-Huai-Hai region through the Guanzhong Plain and the NanXiang Plain. Meanwhile, the pathogen was also spread eastward from the southwestern region to the lower reaches of the Yangtze River, utilizing the Jianghan Plain as a bridge and the Yangtze River Valley in southwestern Anhui as the main pathway. Furthermore, the pathogen spread northward into Shandong under the driving force of the southeast winds. The findings of this study may provide valuable insights for the integrated management of wheat stripe rust in China.