Rust Resistance Research Articles

Resistance of Modern Russian Winter Wheat Cultivars to Yellow Rust.

Over the last decade, the significance of yellow rust caused by Puccinia striiformis (Pst) has substantially increased worldwide, including in Russia. The development and cultivation of resistant genotypes is the most efficient control method. The present study was conducted to explore the yellow rust resistance potential of modern common winter wheat cultivars included in the Russian Register of Breeding Achievements in 2019-2022 using the seedling tests with an array of Pst races and molecular markers linked with Yr resistance genes. Seventy-two winter wheat cultivars were inoculated with five Pst isolates differing in virulence and origin. Molecular markers were used to identify genes Yr2, Yr5, Yr7, Yr9, Yr10, Yr15, Yr17, Yr18, Yr24, Yr25 and Yr60. Thirteen cultivars were resistant to all Pst isolates. The genes Yr5, Yr10, Yr15 and Yr24 that are effective against all Russian Pst races in resistant cultivars were not found. Using molecular methods, gene Yr9 located in translocation 1BL.1RS was detected in 12 cultivars, gene Yr18 in 24, gene Yr17 in 3 and 1AL.1RS translocation with unknown Yr gene in 2. While these genes have lost effectiveness individually, they can still enhance genetic diversity and overall yellow rust resistance, whether used in combination with each other or alongside other Yr genes.

Exploring the trait‐yield association patterns in different oat mega‐environments of Canada

AbstractThis article presents a graphical method to visually analyze the trait–yield association (TYA) patterns based on data from multi‐location, multi‐year crop variety trials, exemplified using oat data from trials conducted across Canada from 2017 to 2022. Each year a new set of 60–66 oat (Avena sativa L.) breeding lines were tested in replicated yield trials at 9–11 locations, and data for yield, key agronomic and quality traits, and crown rust scores were collected at all or some of the locations. Pearson correlation coefficient was calculated between yield and each trait for each trial. The correlation coefficients from different locations and years were arranged in a TYA × trial (TYT) two‐way table. This table was subjected to singular value decomposition, and the resulting first two principal components were used to generate a TYT biplot. The TYT biplot revealed three oat mega‐environments (MEs) in Canada, consistent with the conclusion from previous ME analyses, indicating that each ME had its characteristic TYA patterns. It was found that yield was consistently and positively correlated with crown rust (Puccinia coronata var. avenae) resistance, test weight, kernel weight, and groat content in ME1 (the crown rust‐prone regions of Ontario); yield was correlated positively with plant height but negatively with oil content in ME2 (the northern regions of eastern Canada). Interestingly, crown rust resistance was found to contribute negatively to yield in ME2. No strong and consistent TYAs were found in ME3 (the Canadian prairies). Different types of TYAs have different uses in genotypic selection.

Genome-wide association study of Asian and European common wheat accessions for yield-related traits and stripe rust resistance.

Identifying novel loci of yield-related traits and resistance to stripe rust (caused by Puccinia striiformis f. sp. tritici) in wheat will help in breeding wheat that can meet projected demands in diverse environmental and agricultural practices. We performed a genome-wide association study with 24,767 SNPs in 180 wheat accessions that originated in 16 Asian or European countries between latitudes 30°N and 45°N. We detected seven accessions with desirable yield-related traits and 42 accessions that showed stable, high degrees of stripe rust resistance in multi-environment field assessments. A marker-trait association analysis of yield-related traits detected 18 quantitative trait loci (QTLs) in at least two test environments and two QTLs related to stripe rust resistance in at least three test environments. Five of these QTLs were identified as potentially novel QTLs by comparing their physical locations with those of known QTLs in the Chinese Spring (CS) reference genome RefSeq v1.1 published by the International Wheat Genome Sequencing Consortium; two were for spike length, one was for grain number per spike, one was for spike number, and one was for stripe rust resistance at adult plant stage. We also identified 14 candidate genes associated with the five novel QTLs. These QTLs and candidate genes will provide breeders with new germplasm and can be used to conduct marker-assisted selection in breeding wheat with improved yield and stripe rust resistance.

Integrated Transcriptome and Metabolome Analysis Reveals the Molecular Mechanism of Rust Resistance in Resistant (Youkang) and Susceptive (Tengjiao) Zanthoxylum armatum Cultivars.

Chinese pepper rust is a live parasitic fungal disease caused by Coleosporium zanthoxyli, which seriously affects the cultivation and industrial development of Z. armatum. Cultivating and planting resistant cultivars is considered the most economical and environmentally friendly strategy to control this disease. Therefore, the mining of excellent genes for rust resistance and the analysis of the mechanism of rust resistance are the key strategies to achieve the targeted breeding of rust resistance. However, there is no relevant report on pepper rust resistance at present. The aim of the present study was to further explore the resistance mechanism of pepper by screening the rust-resistant germplasm resources in the early stage. Combined with the analysis of plant pathology, transcriptomics, and metabolomics, we found that compared with susceptible cultivar TJ, resistant cultivar YK had 2752 differentially expressed genes (DEGs, 1253 up-, and 1499 downregulated) and 321 differentially accumulated metabolites (DAMs, 133 up- and 188 down-accumulated) after pathogen infection. And the genes and metabolites related to phenylpropanoid metabolism were highly enriched in resistant varieties, which indicated that phenylpropanoid metabolism might mediate the resistance of Z. armatum. This finding was further confirmed by a real-time quantitative polymerase chain reaction analysis, which revealed that the expression levels of core genes involved in phenylpropane metabolism in disease-resistant varieties were high. In addition, the difference in flavonoid and MeJA contents in the leaves between resistant and susceptible varieties further supported the conclusion that the flavonoid pathway and methyl jasmonate may be involved in the formation of Chinese pepper resistance. Our research results not only help to better understand the resistance mechanism of Z. armatum rust but also contribute to the breeding and utilization of resistant varieties.

Synthesis of Polymer-Grafted Carbon Dots Serving as Multifunctional Lubricant Additives with Excellent Tribological Performance and Additional Rust Resistance Function for Steel/Steel Contact.

Poly(bis(2-ethylhexyl) phosphoric) methacrylic anhydride-grafted carbon dots (CD-g-PEPMA) have been controllably synthesized and used as multifunctional lubricant additives of poly(ethylene glycol) (PEG200). The polymers on the surfaces of CD-g-PEPMA not only endow them with particularly excellent dispersion stability but also enhance their adsorbability on the steel surface and embedded stability between the rubbing surfaces. Hence, CD-g-PEPMA as an additive showed outstanding rust resistance and tribological performance. Among CD-g-PEPMA-X (X represents the polymerization time), CD-g-PEPMA-2 (X = 2 h) exhibited the best tribological performance. At the optimum c of 2.0 wt %, CD-g-PEPMA-2 reduced the coefficient of friction and wear volume of PEG200 by 60.1 and 74.0%, respectively. The striking friction-reducing and antiwear functions of CD-g-PEPMA as additives can be attributed to the synergistic lubrication effect of carbon cores and polymers. The rolling, polishing, and mending effects of carbon cores combined with the favorable adsorbability and reactivity of polymers on steel surfaces synergistically induced the formation of boundary lubrication films on wear track surfaces. The films are composed of tribochemical reaction products such as Fe2(CO3)3, Fe3C, and FePO4 embedded with carbon cores, tremendously reducing the friction and wear of the friction pair. The research results can provide substantial theoretical guidance and data support for designing and developing high-efficiency polymer-CD integrative multifunctional nanoadditives toward PEG.

Cloning of the wheat leaf rust resistance gene Lr47 introgressed from Aegilops speltoides

Leaf rust, caused by Puccinia triticina Eriksson (Pt), is one of the most severe foliar diseases of wheat. Breeding for leaf rust resistance is a practical and sustainable method to control this devastating disease. Here, we report the identification of Lr47, a broadly effective leaf rust resistance gene introgressed into wheat from Aegilops speltoides. Lr47 encodes a coiled-coil nucleotide-binding leucine-rich repeat protein that is both necessary and sufficient to confer Pt resistance, as demonstrated by loss-of-function mutations and transgenic complementation. Lr47 introgression lines with no or reduced linkage drag are generated using the Pairing homoeologous1 mutation, and a diagnostic molecular marker for Lr47 is developed. The coiled-coil domain of the Lr47 protein is unable to induce cell death, nor does it have self-protein interaction. The cloning of Lr47 expands the number of leaf rust resistance genes that can be incorporated into multigene transgenic cassettes to control this devastating disease.

Postulation of leaf rust resistance genes in Indian and exotic wheat germplasm using near-isogenic lines (NILs) and molecular markers

Leaf rust caused by Puccinia triticina Eriks. (Pt) is one of the most devastating fungal diseases affecting wheat (Triticum aestivum L.) production worldwide. Deployment of resistant cultivars is a prominent eco-friendly approach to manage this disease. But major constraint in this case is emergence of new pathotypes of pathogen due to faster evolution. Widening the gene pool by gene mining from diverse panel is the key strategy to keep pace with the ever-evolving pathogen. So, in this study attempts were made to identify leaf rust resistance genes in a selected set of 149 germplasm lines by seedling reaction test against two most prevalent Pt pathotypes, 77–9 (MHTKL) and 77–5 (THTTM) and for field resistance at Ludhiana and Gurdaspur during 2018–2021. Based on seedling infection type (IT) data, 88 lines were found resistant (low IT; 0–2) and 39 lines were susceptible (high IT; ≥3). Under field conditions, 77 lines showed highly resistance response across the locations and years. Gene postulation in the test germplasm was done by gene matching technique and further confirmed by linked molecular markers; which revealed the presence of 11 Lr genes singly or in combinations. Leaf rust resistance gens; Lr9, Lr19, Lr24, Lr34, Lr37, Lr42, Lr45, Lr52, Lr57, Lr58 and Lr76 were detected in 4, 7, 10, 1, 7, 33, 41, 44, 2, 24 and 6 lines respectively. The present study's resistant germplasm lines can be utilised as resistant parents in crosses intended for pyramiding and the deployment of leaf rust resistance genes.

Identification of southern corn rust resistance QTNs in Chinese summer maize germplasm via multi-locus GWAS and post-GWAS analysis.

Southern corn rust (SCR) caused by Puccinia polysora Underw is a major disease leading to severe yield losses in China Summer Corn Belt. Using six multi-locus GWAS methods, we identified a set of SCR resistance QTNs from a diversity panel of 140 inbred lines collected from China Summer Corn Belt. Thirteen QTNs on chromosomes 1, 2, 4, 5, 6, and 8 were grouped into three types of allele effects and their associations with SCR phenotypes were verified by post-GWAS case-control sampling, allele/haplotype effect analysis. Relative resistance (RRR) and relative susceptibility (RRs) catering to its inbred carrier were estimated from single QTN and QTN-QTN combos and epistatitic effects were estimated for QTN-QTN combos. By transcriptomic annotation, a set of candidate genes were predicted to be involved in transcriptional regulation (S5_145, Zm00001d01613, transcription factor GTE4), phosphorylation (S8_123, Zm00001d010672, Pgk2- phosphoglycerate kinase 2), and temperature stress response (S6_164a/S6_164b, Zm00001d038806, hsp101, and S5_211, Zm00001d017978, cellulase25). The breeding implications of the above findings were discussed.

Candidate effectors for leaf rust resistance gene Lr28 identified through transcriptome and in-silico analysis.

Puccinia spp. causing rust diseases in wheat and other cereals secrete several specialized effector proteins into host cells. Characterization of these proteins and their interaction with host's R proteins could greatly help to limit crop losses due to diseases. Prediction of effector proteins by combining the transcriptome analysis and multiple in-silico approaches is gaining importance in revealing the pathogenic mechanism. The present study involved identification of 13 Puccinia triticina (Pt) coding sequences (CDSs), through transcriptome analysis, that were differentially expressed during wheat-leaf rust interaction; and prediction of their effector like features using different in-silico tools. NCBI-BLAST and pathogen-host interaction BLAST (PHI-BLAST) tools were used to annotate and classify these sequences based on their most closely matched counterpart in both the databases. Homology between CDSs and the annotated sequences in the NCBI database ranged from 79 to 94% and with putative effectors of other plant pathogens in PHI-BLAST from 24.46 to 54.35%. Nine of the 13 CDSs had effector-like features according to EffectorP 3.0 (≥0.546 probability of these sequences to be effector). The qRT-PCR expression analysis revealed that the relative expression of all CDSs in compatible interaction (HD2329) was maximum at 11 days post inoculation (dpi) and that in incompatible interactions (HD2329 + Lr28) was maximum at 3 dpi in seven and 9 dpi in five CDSs. These results suggest that six CDSs (>0.8 effector probability as per EffectorP 3.0) could be considered as putative Pt effectors. The molecular docking and MD simulation analysis of these six CDSs suggested that candidate Lr28 protein binds more strongly to candidate effector c14094_g1_i1 to form more stable complex than the remaining five. Further functional characterization of these six candidate effectors should prove useful for a better understanding of wheat-leaf rust interaction. In turn, this should facilitate effector-based leaf rust resistance breeding in wheat.

Registration of HA‐R20 and HA‐R21 confection sunflower germplasms resistant to rust and downy mildew

AbstractRust and downy mildew (DM) are detrimental diseases in global sunflower (Helianthus annuus L.) production. Disease often results in yield loss and reduced seed quality. Host resistance to DM and rust is mediated by single dominant genes in sunflower. To better utilize genetic resistance, gene pyramiding is a common practice in crop breeding to extend the durability and longevity of resistance. Two confection sunflower germplasm lines, HA‐R20 (Reg. no. GP‐387, PI 702361) and HA‐R21 (Reg. no. GP‐388, PI 702362), were developed using the pedigree breeding method and DNA marker‐assisted selection and released by the USDA‐ARS Sunflower and Plant Biology Research Unit in collaboration with the North Dakota Agricultural Experiment Station in September 2022. HA‐R20 is an F3‐derived F4 confection restorer selection from the cross of HA‐DM2 and HA‐R8, carrying rust resistance genes R12 and R15 and DM resistance gene PlArg. HA‐R21 is an F3‐derived F4 confection maintainer selection from the cross of HA‐DM3 and HA‐R8, carrying rust resistance genes R13a and R15 and DM resistance gene Pl17. Disease reaction and marker testing for DM and rust confirmed that both germplasms harbor DM and rust R genes in the homozygous condition and are resistant to all DM and rust races identified in North America to date. These multiple disease‐resistant lines will provide the sunflower industry with durable disease‐resistant sources for the continued improvement of the crop.

Characterization of Pre-Breeding Wheat (Triticum aestivum L.) Germplasm for Stripe Rust Resistance Using Field Phenotyping and Genotyping.

Wheat is highly affected by stripe rust disease, particularly under cooler environments, and the losses can reach up to 100 percent depending on the intensity of infection and the susceptibility of the genotype. The most effective method to manage this disease is the use of resistant varieties. In the present study, 192 wheat genotypes were evaluated for stripe rust resistance under field conditions and also in a laboratory using molecular markers. These lines included pre-breeding germplasm developed for rust resistance and some high-yielding commercially grown wheat varieties. Out of 192 genotypes, 53 were found to be resistant, and 29 showed moderate resistance reaction under field conditions, whereas the remaining genotypes were all either moderately susceptible or susceptible. Under controlled conditions, out of 109 genotypes, only 12 were found to be resistant to all the six virulent/pathogenic pathotypes. Additionally, a selection of 97 genotypes were found resistant in field screening and were subjected to molecular validation using the markers linked to major R-genes, viz., Yr5, Yr10, Yr15 and Yr17. Nine genotypes possessed the Yr5 gene, twelve had the Yr10 gene, fourteen had the Yr15 gene and thirty-two had the Yr17 gene. The resistance genes studied in the current study are effective in conferring resistance against stripe rust disease. The genotypes identified as resistant under both field and controlled conditions can be used as sources in stripe rust resistance breeding programs.

Characteristics of the efficiency of leaf rust resistance genes of spring wheat in the conditions of the Republic of Tatarstan

Leaf rust is a harmful wheat disease of, which is annually identified in crops in the territory of the Republic of Tatarstan. The disease resistance of the varieties is controlled by Lr genes, of which more than 70 are known at present. Most of them have lost their effectiveness. The purpose of the current work was to study the efficiency of 54 leaf rust resistance genes and their combinations from 2011 to 2022. The object of the study was a set of isogenic lines and test-varieties with identified Lr genes. The damage degree by leaf rust was estimated according to the maximum infestation, identified in the period ‘milk – beginning of a kernel wax ripeness’ under conditions of a natural infectious background. The damage degree by leaf rust was determined as a percentage according to the Peterson scale. There has been established that the genes Lr 19, Lr 38, Lr 47, Lr 49, Lr Ag (i), Lr Ku keep showing high efficiency in the conditions of the Republic of Tatarstan. The efficiency of the gene Lr 19 has increased in pyramids with genes Lr 26, Lr 23, Lr 14a, and Lr Bz. Monogenic resistance to leaf rust has been maintained for 12 years in the sample ‘Pavon derivative’ (PI 603918), carrying the gene Lr 47. In the period of 2019–2022 there was identified a decrease in wheat damage degree by leaf rust. Though under such conditions, a field estimation of breeding material for resistance cannot guarantee the development of wheat varieties immune to this disease.

Integrative Molecular Approaches to Plant Disease: A Review

Modern molecular and bioinformatics technologies have made understanding host-pathogen interactions easier. Plants have many ways to protect themselves from microbial diseases, such as physical barriers, PAMP detection, and R genes that recognize pathogen-effector proteins and turn on effector-triggered immunity. Plant pathogen genome databases provide genomic and phenotypic data on plant pathogen species and information on plant-pathogen interactions. Map-based or positional gene cloning is improving our understanding of plant-pathogen interactions, with R genes being used to develop resistance to pathogens. Plant genomes typically contain several hundred nucleotide-binding site-leucine-rich repeats (NLRs), with their number, arrangement, and domain combinations varying by species. Bacterial blight (BB) severely impacts rice production, and about 37 of 44 resistance genes have been mapped and 15 cloned. Many disease-resistant wheat cultivars have been developed using powdery mildew leaf rust (Lr) resistance genes from wild relatives of T. aestivum. Over 140 genes are linked to powdery mildew resistance in T. aestivum and MutChromSeq have found new target genes. Cloning Arabidopsis resistance genes is essential for developing resistant cultivars and understanding R gene evolution. Some R genes encode proteins with nucleotide-binding site (NBS) motifs, and an LRR protects against Erysiphe cruciferarum powdery mildew. CRISPR/Cas9 gene editing is a major tool in plant genome editing, efficiently introducing target site mutations and improving plant immunity. High-throughput sequencing can identify and clone candidate resistance genes in different plant species, and gene editing technologies like CRISPR/Cas have illuminated site-specific mutagenesis and durable resistance.

A pathogen-induced putative NAC transcription factor mediates leaf rust resistance in barley

Leaf rust, caused by Puccinia hordei, is one of the most widespread and damaging foliar diseases affecting barley. The barley leaf rust resistance locus Rph7 has been shown to have unusually high sequence and haplotype divergence. In this study, we isolate the Rph7 gene using a fine mapping and RNA-Seq approach that is confirmed by mutational analysis and transgenic complementation. Rph7 is a pathogen-induced, non-canonical resistance gene encoding a protein that is distinct from other known plant disease resistance proteins in the Triticeae. Structural analysis using an AlphaFold2 protein model suggests that Rph7 encodes a putative NAC transcription factor with a zinc-finger BED domain with structural similarity to the N-terminal DNA-binding domain of the NAC transcription factor (ANAC019) from Arabidopsis. A global gene expression analysis suggests Rph7 mediates the activation and strength of the basal defence response. The isolation of Rph7 highlights the diversification of resistance mechanisms available for engineering disease control in crops.

Identification and Molecular Mapping of the Gene YrFL in Wheat Cultivar Flanders with Durable Resistance to Stripe Rust.

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most severe diseases of wheat (Triticum aestivum L.) worldwide. Identification and characterization of resistance genes is advantageous to cultivating wheat varieties with durable resistance, which is the most economic and effective strategy to control stripe rust. Flanders, a common wheat cultivar released in France in 1986, confers effective resistance to stripe rust both at the seedling and adult plant stages. To elucidate the genetic basis of resistance in Flanders, F1, F2, and F2:3 generations derived from the cross Mingxian169 × Flanders were evaluated with the most prevalent Chinese Pst race CYR33 at the seedling stage. Inheritance analysis showed that the stripe rust resistance of Flanders was controlled by a single dominant gene, temporarily designated as YrFL. Bulked segregant analysis (BSA) combined with a wheat 660K single-nucleotide polymorphism (SNP) array indicated that polymorphic SNP markers were mainly located in the 0 to 150 Mb on wheat chromosome 5A. One hundred and eleven kompetitive allele-specific PCR (KASP) and 39 simple sequence repeat (SSR) markers on chromosome 5A were used to locate the YrFL. Linkage analysis mapped YrFL with 19 KASP and three SSR markers on wheat chromosome 5AS, and the genetic distances of the closest flanking markers AX108925494 and Xbarc56 to YrFL were 0.6 and 2.0 cM, respectively. Chromosome location, resistance characterization, and molecular marker positions indicated that YrFL is likely a novel stripe rust resistance gene on wheat chromosome 5AS and could be pyramided with other resistance genes to improve resistance in wheat breeding programs.

Obtaining dihaploid lines of soft winter wheat with complex resistance to rust and hard smut by anther culture in vitro

Aim. Obtaining homozygous linear material of winter soft wheat of different genetic origin (complex hybrids), which are resistant to different types of rust by androgenesis in vitro. Methods. In vitro culture of isolated anthers of wheat. The percentage of callus and regeneration of green plants for each genotype calculated as a percentage of the planted anthers. Methods of phytopathological assessment of resistance to complex of various diseases. Results. The differences in the frequency of сallus induction (from 0.99 to 16.26 % of planted anthers) and the ability to regenerate plants (from 0 to 3.05 % of planted anthers) in the process of androgenesiss in vitro of winter soft wheat were detected. Fertile regenerants in the anthers culture 5 out of 9 studied hybrids have been obtained. The effectiveness of the last process was different: from 12.5 to 60.0 % (an average of 29.41 %) from the received regenerants. The high degree (8–9 points) of the resistance of the obtained dihaploids to a complex of diseases was shown. Conclusions. Genotype-specific of microspores morphogenetic reactions of soft winter wheat in the process of androgenesis in vitro were revealed. The highest level of callus formation were shown for samples 120/20 and 132/20. 15 dihaploid lines with complex rust resistance and hard smut were obtained.

Plant and pathogen genomics: essential approaches for stem rust resistance gene stacks in wheat.

The deployment of disease resistance genes is currently the most economical and environmentally sustainable method of crop protection. However, disease resistance genes can rapidly break down because of constant pathogen evolution, particularly when they are deployed singularly. Polygenic resistance is, therefore, considered the most durable, but combining and maintaining these genes by breeding is a laborious process as effective genes are usually unlinked. The deployment of polygenic resistance with single-locus inheritance is a promising innovation that overcomes these difficulties while enhancing resistance durability. Because of major advances in genomic technologies, increasing numbers of plant resistance genes have been cloned, enabling the development of resistance transgene stacks (RTGSs) that encode multiple genes all located at a single genetic locus. Gene stacks encoding five stem rust resistance genes have now been developed in transgenic wheat and offer both breeding simplicity and potential resistance durability. The development of similar genomic resources in phytopathogens has advanced effector gene isolation and, in some instances, enabled functional validation of individual resistance genes in RTGS. Here, the wheat stem rust pathosystem is used as an illustrative example of how host and pathogen genomic advances have been instrumental in the development of RTGS, which is a strategy applicable to many other agricultural crop species.

POSTULATION OF YR RESISTANCE GENES TO STRIPE RUST IN 12 COMMERCIAL WHEAT CULTIVARS OF RUSSIAN BREEDING

Stripe rust (Puccinia striiformis f. sp. tritici) is a common wheat disease of economic importance in all world wheat production regions. In most of the regions stripe rust causes yield losses of 10-70 %, depending on the time infection occur, host susceptibility, disease development, and the duration of the epidemics. In South Russia even in unfavourable conditions for the pathogen, stripe rust occurred in the region every year, and in some areas there are foci of the disease with of up to 50% severity.
 Phytopathological testing is one of the least expensive and most effective methods for the rapid identification of juvenile resistance genes in varieties against pathogens. It allows to obtain detailed information about the genetics of the host and pathogen in a short time. In the research Yr resistant genes and its combinations were postulated in winter wheat varieties of Russian breeding to North-Caucasus population of stripe rust by this method.
 Purpose of this study was identification of known stripe rust resistance genes in 12 commercial winter wheat cultivars by phytopathological testing.
 Material and methods: The postulation of known resistance genes was carried out in a greenhouse complex (seedling stage) and at the research station (adult plant stage) of the Laboratory of Plant Immunity to Diseases of the Federal Scientific Center for Biological Plant Protection (Krasnodar).
 For postulation, we chose the method by Dubin et al. (1989), based on the comparison of response types of differential cultivars and studied varieties to Pst isolates.
 Results. In 10 out of 12 winter wheat varieties of Russian breeding, 13 stripe rust resistance genes and their combinations were postulated.: Yr3, Yr3a, Yr6, Yr32, Yr2+6, Yr2+9, Yr39+Alp, Yr4+12, Yr4b, Yr3a+4a+H46, YrA, YrSp, YrSU. The following resistance genes have not been identified: Yr2, Yr5, Yr10, Yr10+Mor, Yr24, Yr27, Yr25+32, since no isolates virulent to carriers of these genes were isolated from the North Caucasian population of P. striiformis; and they are highly effective against this population. Highly effective (Yr3, Yr2+9, Yr3a, Yr4+12, Yr3a+4a+H46) resistance genes were identified in the Kurs, Morozko, and Step’ varieties. We note a combination of effective Yr2+6 genes in the Gurt variety.
 In field conditions, high resistance (degree of damage up to 10%) to the North Caucasian population of the stripe rust pathogen was shown by lines and differential cultivars containing the following resistance genes: Yr2, Yr3, Yr8, Yr10, Yr24, Yr25, Yr27, Yr10+Mor, Yr3a, Yr25+32, Yr3a+4a+H46, Yr3с+Min, Yr4+12, Yr7+25, Yr8+19, 8+6+25, YrSp. Due to the low degree of damage, these genes and their combinations are classified as highly effective and can be involved in the breeding process to create new resistant varieties. Varieties containing these genes can also be recommended for breeders and used in production for effective disease control.

Genetic mapping of the wheat leaf rust resistance gene Lr19 and development of translocation lines to break its linkage with yellow pigment.

The leaf rust resistance gene Lr19, which is present on the long arm of chromosome 7E1 in Thinopyrum ponticum, was mapped within a 0.3-cM genetic interval, and translocation lines were developed to break its linkage with yellow pigmentation The leaf rust resistance locus Lr19, which was transferred to wheat (Triticum aestivum) from its relative Thinopyrum ponticum in 1966, still confers broad resistance to most known races of the leaf rust pathogen Puccinia triticina (Pt) worldwide. However, this gene has not previously been fine-mapped, and its tight linkage with a gene causing yellow pigmentation has limited its application in bread wheat breeding. In this study, we genetically mapped Lr19 using a bi-parental population from a cross of two wheat-Th. ponticum substitution lines, the Lr19-carrying line 7E1(7D) and the leaf rust-susceptible line 7E2(7D). Genetic analysis of the F2 population and the F2:3 families showed that Lr19 was a single dominant gene. Genetic markers allowed the gene to be mapped within a 0.3-cM interval on the long arm of Th. ponticum chromosome 7E1, flanked by markers XsdauK3734 and XsdauK2839. To reduce the size of the Th. ponticum chromosome segment carrying Lr19, the Chinese Spring Ph1b mutant was employed to promote recombination between the homoeologous chromosomes of the wheat chromosome 7D and the Th. ponticum chromosome 7E1. Two translocation lines with short Th. ponticum chromosome fragments carrying Lr19 were identified using the genetic markers closely linked to Lr19. Both translocation lines were resistant to 16 Pt races collected throughout China. Importantly, the linkage between Lr19 and yellow pigment content was broken in one of the lines. Thus, the Lr19 linked markers and translocation lines developed in this study are valuable resources in marker-assisted selection as part of common wheat breeding programs.

Genome-wide QTL mapping for stripe rust resistance in spring wheat line PI 660122 using the Wheat 15K SNP array.

Stripe rust is a global disease of wheat. Identification of new resistance genes is key to developing and growing resistant varieties for control of the disease. Wheat line PI 660122 has exhibited a high level of stripe rust resistance for over a decade. However, the genetics of stripe rust resistance in this line has not been studied. A set of 239 recombinant inbred lines (RILs) was developed from a cross between PI 660122 and an elite Chinese cultivar Zhengmai 9023. The RIL population was phenotyped for stripe rust response in three field environments and genotyped with the Wheat 15K single-nucleotide polymorphism (SNP) array. A total of nine quantitative trait loci (QTLs) for stripe rust resistance were mapped to chromosomes 1B (one QTL), 2B (one QTL), 4B (two QTLs), 4D (two QTLs), 6A (one QTL), 6D (one QTL), and 7D (one QTL), of which seven QTLs were stable and designated as QYrPI660122.swust-4BS, QYrPI660122.swust-4BL, QYrPI660122.swust-4DS, QYrPI660122.swust-4DL, QYrZM9023.swust-6AS, QYrZM9023.swust-6DS, and QYrPI660122.swust-7DS. QYrPI660122.swust-4DS was a major all-stage resistance QTL explaining the highest percentage (10.67%-20.97%) of the total phenotypic variation and was mapped to a 12.15-cM interval flanked by SNP markers AX-110046962 and AX-111093894 on chromosome 4DS. The QTL and their linked SNP markers in this study can be used in wheat breeding to improve resistance to stripe rust. In addition, 26 lines were selected based on stripe rust resistance and agronomic traits in the field for further selection and release of new cultivars.