Plasmopara Halstedii Research Articles

Optimization of loop-mediated isothermal amplification assay for sunflower mildew disease detection

Loop-Mediated Isothermal Amplification (LAMP) represents a valuable technique for DNA/RNA detection, known for its exceptional sensitivity, specificity, speed, accuracy, and affordability. This study focused on optimizing a LAMP-based method to detect early signs of Plasmopara halstedii, the casual pathogen of sunflower downy mildew, a severe threat to sunflower crops. Specifically, a set of six LAMP primers (two outer, two inner, and two loop) were designed from P. halstedii genomic DNA, targeting the ribosomal Large Subunit (LSU). These primers were verified by in silico analysis and experimental validation using both target and non-target species' DNAs. Optimizations encompassing reaction conditions (temperature, time) and component concentrations (magnesium, Bst DNA polymerase, primers, and dNTP) were determined. Validation of these optimizations was performed by agarose gel electrophoresis. Furthermore, various colorimetric chemicals (Neutral Red, Hydroxynaphthol Blue, SYBR Safe, Thiazole Green) were evaluated to facilitate method analysis, and the real-time analysis has been optimized, presenting multiple approaches for detecting sunflower downy mildew using the LAMP technique. The analytical sensitivity of the method was confirmed by detecting P. halstedii DNA concentrations as low as 0.5 pg/μl. This pioneering study, establishing P. halstedii detection through the LAMP method, stands as unique in its field. The precision, robustness, and practicality of the LAMP protocol make it an ideal choice for studies focusing on sunflower mildew, emphasizing its recommended use due to its operational ease and reliability.

Characterization of Argentinian wild Helianthus annuus populations in their responses to Plasmopara halstedii infection

The pathogen Plasmopara halstedii, causing downy mildew (DM), is a widespread sunflower disease which can be controlled by single dominant genes. Wild Helianthus annuus have been a valuable source of vertical resistance to control P. halstedii, but such resistance may eventually be overcome by new races of the pathogen. Alternatively, quantitative, or partial resistance, is more stable and may be combined with vertical resistance to prevent DM outbreaks. We assessed the responses of six populations of wild H. annuus naturalized in Argentina to race 710 of P. halstedii. We examined: 1) the aerial phenotype (including seedling death) using two damage scales and three disease indices, 2) the growth of the pathogen along the hypocotyls, and 3) the presence of the pathogen in the root system. We found that the evaluated sunflower wild populations had lower disease levels than the susceptible cultivated controls. A histologic analysis showed that the wild H. annuus seedlings showed cellular reactions (e.g. necrosis and the deposit of materials on the walls of invaded cells) to restrict the pathogen’s growth, allowing the identification of two possible types of resistance: type I, when the growth of the pathogen was limited to the base of the hypocotyls, and type II, when the pathogen managed to invade the entire length of the hypocotyls. The wild sunflower populations also showed differential responses to root infections. A quantitative or partial genetic resistance, rather than resistance based on major genes, seems to be operating in the sampled populations. The individuals found to be resistant in each population represent promising germplasm for sunflower breeding.

Identification of the Downy Mildew Resistant Sources in Sunflower

Four different evaluation trials were conducted in the field between 2017 and 2020, with varied numbers of genotypes, to evaluate the performance of sunflower genotypes for agromorphological features and resistance to Sunflower Downy Mildew (SDM) at Latur, Maharashtra, India. A validation experiment was carried out in 2021–2022, using artificial screening in National Diseased Plot Screening Facility at Latur, to screen a small number of accessions that had previously shown resistance to SDM during 2017-2020. The released variety "Morden," also susceptible check showed at least 60% of the SDM incidence for four years. This suggests that Plasmopara halstedii spores could be present in the experimental soils, which increases the variety's susceptibility to SDM disease. Out of the tree genotypes that were reported to be resistant in field screening viz., GMU-481 (GP1 909 genotype), Ec-198078, and RHA 1-1 (selection) only two GMU-481 (GP1 909) and Ec-198078 were verified to be resistant under artificial screening in 2021–2022 and can be designated as sources of resistance for SDM disease. These two genotypes with resistance to SDM could be used in future breeding attempts and as potential gene donors for SDM.

Characterizing the Dynamics of Virulence and Fungicide Resistance of Phytophthora capsici in Michigan Vegetable Fields Reveals Loci Associated with Virulence.

The oomycete Phytophthora capsici is a destructive pathogen infecting more than 50 plant species and is one of the most serious threats to cucurbit production. Phytophthora blight caused by Phytophthora capsici can affect all plant growth stages, and fungicides and cultural controls are used to limit losses. Dissecting pathogen virulence and fungicide resistance can provide insights into pathogenic mechanisms and inform effective management practices to control P. capsici. In this study, we assessed virulence, mefenoxam sensitivity, and genetic diversity of nine P. capsici populations collected from Cucurbitaceae, Solanaceae, and Fabaceae host families in Michigan from 2002 to 2016. We developed 992 simple sequence repeats (SSRs) in the P. capsici genome and identified 60 SSRs located within or close to RXLR-class (Arginine-any amino acid-Leucine-Arginine) effectors and 29 SSRs within or close to effector CRN (CRinkling and Necrosis) family protein, which represent 62 RXLR and 34 putative CRNs. Population structure analysis shows that mefenoxam resistance was not associated with the year of collection, host type, or location, but there were significant differences in virulence among the populations. Using the general linear model and mixed linear model-based association analyses with all effector-related SSR markers, we identified four SSR markers significantly associated with at least one of the virulence-related parameters. Of these, one (Pce_SC18) was in a predicted CRN effector and had high identity with the putative PhCRN37 effector in the pathogen Plasmopara halstedii, which can be further verified for virulence identification in P. capsici.

Efficacy of some plant resistance inducers against several sunflower downy mildew (Plasmopara halstedii (Farl.) Berl. et de Toni) isolates

Plasmopara halstedii (Farl.) Berl. et de Toni is the oomycete that causes sunflower downy mildew (SDM). Traditional means of controlling this pathogen are using resistant hybrids, crop rotation and seed coating with fungicides. Disease control strategies that use a variety of approaches are becoming an increasingly essential aspect of pest management strategies. We conducted this exploratory investigation to evaluate whether specific plant resistance inducers might work against P. halstedii. In this study we used azadirachtin (AZA) a botanical insecticide; benzothiadiazole (BTH) and Trichoderma asperellum. Three-day-old susceptible sunflower seedlings were pre-treated with different doses of inducers for two hours. The seedlings were immediately inoculated of 7 different pathotype of P. halstedii. As a control, metalaxyl-M a systemic fungicide was used. Nine-day-old sunflower plant leaves were sprayed with bidistilled water to stimulate sporangial growth. In vivo experiments showed that BTH, T. asperellum and the highest doses of AZA significantly reduced downy mildew symptoms. The various pathotypes of the pathogen significantly affected the plant height and disease symptoms under experiments.

Plasmopara echinaceae, a new species of downy mildew affecting cone flowers (Echinacea purpurea) in the United States.

Downy mildew is one of the most important diseases of commercial sunflower and other Asteraceae hosts, including ornamental Rudbeckia. Plasmopara halstedii has historically been identified as the causal agent of this disease, considered a complex of species affecting nearly 35 genera in various tribes. However, with the use of molecular DNA characters for phylogenetic studies, distinct lineages of P. halstedii in the Asteraceae have been identified, confirmed as distinct or segregated as new species. During August of 2022, a downy mildew was observed on potted Echinacea purpurea grown in a retail greenhouse in Jefferson County, Wisconsin, USA. Phylogenetic analyses of the cytochrome c oxidase subunit 2 (cox2) and nuclear large subunit ribosomal RNA (nc LSU rDNA) gene regions indicated these Plasmopara sp. isolates are not conspecific with P. halstedii. Based on phylogenetic evidence and new host association, the Plasmopara isolates from E. purpurea are here described as Plasmopara echinaceae. Diagnostic morphological characters for this new species were not observed when compared with other isolates of P. halstedii or other Plasmopara species found on Asteraceae hosts, and therefore a list of species-specific substitutions in the cox2 region are provided as diagnostic characters. As this study corresponds to the first observation of downy mildew in cone flowers, it is recommended to follow the required disease prevention guidelines to prevent outbreaks and the establishment of this plant pathogen in production sites. Citation: Salgado-Salazar C, Romberg MK, Hudelson B (2023). Plasmopara echinaceae, a new species of downy mildew affecting cone flowers (Echinacea purpurea) in the United States. Fungal Systematics and Evolution 12: 203-217. doi: 10.3114/fuse.2023.12.10.

Registration of HA‐DM15 and HA‐DM16 oilseed sunflower germplasms with resistance to sunflower downy mildew

AbstractSunflower (Helianthus L.) production ranked third in global oilseed production in 2021. Downy mildew (DM), caused by the oomycete pathogen Plasmopara halstedii (Farl.) Berl. et de Toni, is a major constraint for worldwide sunflower production, causing significant yield losses in susceptible hybrids. The search for new sources of resistance to DM is the primary objective of all sunflower breeding programs. Germplasms HA‐DM15 (Reg. no. GP‐385, PI 702359) and HA‐DM16 (Reg. no. GP‐386, PI 702360) were developed by introgressing two new DM resistance genes, Pl37 and Pl38, from the wild sunflower species H. annuus and H. praecox into oilseed sunflower, respectively. The BC1F3‐derived HA‐DM15 harboring the Pl37 gene was selected from the cross of HA 89//NMS HA 89/wild H. annuus PI 435417. The germplasm line HA‐DM16 carrying the Pl38 gene is an improved oilseed derivative of Rf PRA‐417 with DM resistance originally derived from the wild H. praecox PRA‐417 from the cross of cytoplasmic male sterile (CMS) HA89*2/wild H. praecox PRA‐417. HA‐DM15/Pl37 and HA‐DM16/Pl38 are immue to the most predominant and virulent DM races idenfied in North America and Europe. Pl37 and Pl38 have been genetically mapped to sunflower chromosomes 4 and 2, respectively, with single nucleotide polymorphism markers linked to the both genes facilitating their transfer to elite sunflower lines by marker‐assisted selection, providing new and diverse sources for sunflower DM‐resistance breeding.

WAASB-based stability analysis and validation of sources resistant to Plasmopara halstedii race-100 from the sunflower working germplasm for the semiarid regions of India

WAASB-based stability analysis and validation of sources resistant to Plasmopara halstedii race-100 from the sunflower working germplasm for the semiarid regions of India

Conservation of putative transcription factor binding sites of co-expressed Plasmopara halstedii genes in two Phytophthora species

Oomycetes, a large group of fungus-like organisms, include some destructive plant pathogens causing enormous economic damage. Phylogenetically, oomycetes belong to the kingdom Straminipila and have diverse lifestyles, including saprotrophs and both general and specialized pathogens of various eukaryotic supergroups. A rapid increase in genomic studies and next-generation sequencing technologies have led to significant progress in understanding oomycete lifestyles. However, their genetics, including transcriptional regulation, have been studied to a much lesser extent. Here, we provide a cross-species analysis of oomycete promoter for providing a first step towards elucidating gene regulation networks related to pathogenicity and life cycle stages. The clustered DNA sequences of Plasmopara halstedii transcriptome time-series expression level dataset from a preliminary study have been used as a core reference for cross-species comparisons. Using a computational pipeline, 46 potential transcription factor binding site (TFBS) motifs in 25 clusters with functionally conserved downstream genes of downy mildew and two Phytophthora species, regardless of the gene expression levels of Phytophthora transcriptomes, were found. This can now be followed up by knock-out experiments in oomycete species amenable for genetic modification.

Validated Molecular Marker for Downy Mildew Disease Resistance Breeding of Sunflower: A Short Review

The oomycete pathogen Plasmopara halstedii responsible for sunflower downy mildew (DM), that is a significant and important disease that greatly affects the economy. As of now, there is no non-race-specific resistance for this disease and breeders are depended on race-specific resistance to control DM disease. On the other hand, using conventional breeding procedure introgression of the DM resistance genes is a long-term task due to the highly virulent and aggressive nature of the P. halstedii pathogen. Molecular markers that can be applied at the seedling stage, offers rapid response for selection with higher precision as well as a lower cost. There are currently 36 downy mildew resistance genes (R genes), designated as Pl (Pl1-Pl36, Plhra, and PlArg, in sunflowers, each with a unique linkage group (LGs). The availability of DM resistance genomic data of sunflower, related to Single Nucleotide Polymorphisms (SNP) based markers with mine allelic diversity maximize the opportunity of utilizing Marker assisted selection (MAS) techniques for downy mildew resistance breeding. This review highlights the available genetic marker and their utilization at MAS techniques for enhancing downy mildew disease resistant breeding program of sunflowers.

Sunflower Diseases and Downy Mildew (Plasmopara halstedii) in Adana

Sunflower (Helianthus annuus L.) is one of the most important vegetable oil sources in the world and in our country. The preference for sunflower oil in the consumption of vegetable oil increases the importance of sunflowers in our country. Rust, downy mildew, Verticillium wilt, Sclerotinia stalk and head rot, charcoal rot, blight, and leaf spot are some of the important diseases most commonly seen in sunflowers. In some years, depending on the climatic conditions, Downy mildew (Plasmopara halstedii) is widely observed and it causes an epidemic in sunflower-planted areas in the Adana province. Genetically resistant hybrids have started to be grown in Turkey in recent years due to the resistance of downy mildew disease to fungicides. The aim of the study was to determine the status of sunflower diseases and Downy Mildew disease in Adana.

Sunflower (Helianthus annuus L.) breeding for durable resistance to Downy mildew (Plasmopara halstedii)

Abstract Downy mildew is one of the most important diseases of sunflower crop around the world caused by Plasmopara halstedii (Farl.) Berl.et de Toni. The aim of our study is the sunflower hybrid development with the durable resistance to downy mildew, combining one parental line with the most effective for the specific location major gene (Pl 15 for example) and the second parental line – with a high horizontal resistance to downy mildew. Experiments were conducted at All-Russia Research Institute of Oil Crops in 2016–2021. Experimental design was randomized blocks with three replications. CMS-lines with the highest level of horizontal resistance (VK 678, VA 732, VK 680, VK 934, VK 900 and new line SL 0516) were used as mother parents. Lines with Pl 15, resistant to all the downy mildew races were used as pollinators to create sunflower hybrids with durable resistance to downy mildew. A number of high-productive sunflower hybrids with durable resistance to DM (VK 732А × L 642-15, VK 732А × L 634-15, VK 680А × L 642-15, VK 680А × L 634-15, VK 934А × L 642-15 and VK 678А × L 634-15) were developed and tested.

A Recombination Suppressed Region of Sunflower (<i>Helianthus annuus</i> L.) Linkage Group 13 Covers Restoration of Fertility (<i>Rf1</i>) and Downy Mildew Resistance (<i>Pl</i>) Gene Clusters

A number of genes that control valuable for breeding traits introgressed from wild relatives, i.e. pollen fertility restoration, resistance to fungal diseases (downy mildew and rust), are mapped on linkage group 13 of the cultivated sunflower Helianthus annuus L. genome. In sunflower and other plants, the recombination in the chromosome regions containing resistance genes can be suppressed that is favourable for marker assisted selection with applying molecular markers linked to these loci. The joint inheritance of the loci Rf1 (the phenotypic marker is fertility restoration trait) and Pl5/Pl8 conferring resistance to many races of Plasmopara halstedii (Farl) Berl. De Toni (the STS marker Ha-P1) was studied in the F2 generation of hybrids between a sterile line VIR 116A lines and pollen fertility restorers from sunflower VIR collection. In the crossing VIR 116А × VIR 740, the frequency of recombination between the loci Pl5Pl8 and Rf1 constituted 8.61 whereas in the crosses VIR 116А × VIR 195 and VIR 116А × VIR 80 turned out to be twice as high. In all examined F2 populations the absence of phenotypic class of sterile plants possessing paternal Нa-Р1 marker variant was mentioned. It has been shown by the cytological analysis that pollen fertility indices are most probably determined by the plant genotype rather than the male gametophyte allelic constitution. A deficiency of a recombinant F2 class was proposed to be associated with embryonic lethality, i.e. the collapse of zygotes carrying the recessive allele of fertility restoration gene and a specific allele of the resistance (susceptibility) gene obtained from the male parent.

Placing Management of Sunflower Downy Mildew (Plasmopara halstedii (Farl.) Berl. et de Toni) under an Integrated Pest Management (IPM) System Approach: Challenges and New Perspectives

Sunflower is one of the major oil crops in the world. Diseases such as sunflower downy mildew (Plasmopara halstedii (Farl.) Berl. et de Toni) constitute a significant risk factor during sunflower production. Integrated pest management (IPM) is considered an essential tool against sunflower downy mildew; however, the pathogen variability repeatedly affects the efficacy of control measures. This article evaluates some vital elements of the management of sunflower downy mildew disease and analyzes current challenges. In addition, we outlined the options for the future integration of recent research and achievements related to sunflower downy mildew to achieve more sustainable sunflower production. Finally, a SWOT analysis was performed to consider internal factors, such as strengths (S) and weaknesses (W), and external factors, such as opportunities (O) and threats (T) connected to the topic.

Assessing the Sensitivity of Plasmopara halstedii Isolates to Mefenoxam through Host Responses.

Downy mildew caused by Plasmopara halstedii is responsible for significant economic losses in cultivated sunflowers. Field isolates of sunflower downy mildew resistant to mefenoxam, a previously effective active ingredient against the pathogen, have been found across Europe. The main goal of this study was to assess the sensitivity of P. halstedii isolates to mefenoxam through host responses to infection, such as symptoms measured by disease severity and growth reduction, and host tissue reactions, such as hypersensitive reaction and necrosis of invaded cells. Sunflower seeds were treated with Apron XL 350 FS at the European registered rate (3 mg/kg seeds). Seedlings were inoculated using the soil drench method with eight Hungarian P. halstedii isolates. Disease rates and plant heights were measured twice. Histological examinations of cross-sections of sunflower hypocotyls were performed using a fluorescence microscope. In our study, cluster analyses of sunflowers based on macroscopic and microscopic variables showed differentiation of groups of mefenoxam-treated sunflowers inoculated with different P. halstedii isolates. We first revealed a clear difference in host responses of mefenoxam-treated susceptible sunflowers. In addition, examining tissue reactions (e.g., hypersensitive reaction, necrosis) seems more accurate to estimate the sensitivity of P. halstedii isolates to mefenoxam than macroscopic symptoms.

Introgression and targeting of the Pl37 and Pl38 genes for downy mildew resistance from wild Helianthus annuus and H. praecox into cultivated sunflower (Helianthus annuus L.)

Two new downy mildew resistance genes, Pl37 and Pl38, were introgressed from wild sunflower species into cultivated sunflower and mapped to sunflower chromosomes 4 and 2, respectively Downy mildew (DM), caused by the oomycete pathogen Plasmopara halstedii (Farl.) Berl. & de Toni, is known as the most prevalent disease occurring in global sunflower production areas, especially in North America and Europe. In this study, we report the introgression and molecular mapping of two new DM resistance genes from wild sunflower species, Helianthus annuus and H. praecox, into cultivated sunflower. Two mapping populations were developed from the crosses of HA 89/H. annuus PI 435417 (Pop1) and CMS HA 89/H. praecox PRA-417 (Pop2). The phenotypic evaluation of DM resistance/susceptibility was conducted in the BC1F2-derived BC1F3 populations using P. halstedii race 734. The BC1F2 segregating Pop1 was genotyped using an Optimal GBS AgriSeq™ Panel consisting of 768 mapped SNP markers, while the BC1F2 segregating Pop2 was genotyped using a genotyping-by-sequencing approach. Linkage analysis and subsequent saturation mapping placed the DM resistance gene, designated Pl37, derived from H. annuus PI 435417 in a 1.6cM genetic interval on sunflower chromosome 4. Pl37 co-segregated with SNP markers SPB0003 and C4_5738736. Similarly, linkage analysis and subsequent saturation mapping placed the DM resistance gene, designated Pl38, derived from H. praecox PRA-417 in a 0.8cM genetic interval on sunflower chromosome 2. Pl38 co-segregated with seven SNP markers. Multi-pathotype tests revealed that lines with Pl37 or Pl38 are immune to the most prevalent and virulent P. halstedii races tested. Two germplasm lines, HA-DM15 with Pl37 and HA-DM16 with Pl38, were developed for use in sunflower DM-resistance breeding.

High-throughput time series expression profiling of Plasmopara halstedii infecting Helianthus annuus reveals conserved sequence motifs upstream of co-expressed genes

Downy mildew disease of sunflower, caused by the obligate biotrophic oomycete Plasmopara halstedii, can have significant economic impact on sunflower cultivation. Using high-throughput whole transcriptome sequencing, four developmental phases in 16 time-points of Pl. halstedii infecting Helianthus annuus were investigated. With the aim of identifying potential functional and regulatory motifs upstream of co-expressed genes, time-series derived gene expression profiles were clustered based on their time-course similarity, and their upstream regulatory gene sequences were analyzed here. Several conserved motifs were found upstream of co-expressed genes, which might be involved in binding specific transcription factors. Such motifs were also found associated with virulence related genes, and could be studied on a genetically tractable model to clarify, if these are involved in regulating different stages of pathogenesis.

Registration of HA‐DM9, HA‐DM10, and HA‐DM11 oilseed sunflower germplasms with dual resistance to sunflower downy mildew

AbstractDowny mildew (DM), caused by the obligate pathogen Plasmopara halstedii (Farl.) Berl. & de Toni, is a worldwide yield‐limiting disease of sunflower (Helianthus annuus L.). To obtain durable DM resistance in sunflower hybrids, there is a need to stack new resistance genes into the best available germplasm. The DM resistance genes Pl8, Pl17, and Pl18 were recently fine mapped to sunflower chromosomes 13, 4, and 2, respectively. The current study pyramided these genes into a single genotype by marker‐assisted selection. Three oilseed sunflower germplasms, HA‐DM9 (Reg. no. GP‐381, PI 700009), HA‐DM10 (Reg. no. GP‐379, PI 700004), and HA‐DM11 (Reg. no. GP‐380, PI 700005), are dual DM‐resistant germplasm lines developed and have been released by the USDA‐ARS, Sunflower and Plant Biology Research Unit in collaboration with the North Dakota Agricultural Experiment Station in 2021. The three lines, HA‐DM9 (Pl8Pl8/Pl17Pl17), HA‐DM10 (Pl8Pl8/Pl18Pl18), and HA‐DM11 (Pl17Pl17/Pl18Pl18), each stacked two different DM genes, providing broad resistance to all P. halstedii races identified in North America and Europe so far, and can be used in sunflower breeding programs to enhance DM resistance.

A tell tail sign: a conserved C-terminal tail-anchor domain targets a subset of pathogen effectors to the plant endoplasmic reticulum.

The endoplasmic reticulum (ER) is the entry point to the secretory pathway and, as such, is critical for adaptive responses to biotic stress, when the demand for de novo synthesis of immunity-related proteins and signalling components increases significantly. Successful phytopathogens have evolved an arsenal of small effector proteins which collectively reconfigure multiple host components and signalling pathways to promote virulence; a small, but important, subset of which are targeted to the endomembrane system including the ER. We identified and validated a conserved C-terminal tail-anchor motif in a set of pathogen effectors known to localize to the ER from the oomycetes Hyaloperonospora arabidopsidis and Plasmopara halstedii (downy mildew of Arabidopsis and sunflower, respectively) and used this protein topology to develop a bioinformatic pipeline to identify putative ER-localized effectors within the effectorome of the related oomycete, Phytophthora infestans, the causal agent of potato late blight. Many of the identified P. infestans tail-anchor effectors converged on ER-localized NAC transcription factors, indicating that this family is a critical host target for multiple pathogens.

Сцепленное наследование микросателлитного локуса ORS 822 с геном Plarg, контролирующим устойчивость к ложной мучнистой росе, у подсолнечника

Resistance to the downy mildew pathogen Plasmopara halstedii (Farl.) Berlese et de Toni in sunflower is controlled by the resistance gene Pl. The Plarg gene is currently promising in breeding for resistance as it is effective against all known races of the pathogen. This gene is introgressed from the wild species Helianthus argophyllus. Molecular markers and, in particular, simple microsatellite repeats (SSRs) allow to control the transfer and pyramiding of disease resistance genes. However, validation of the molecular marker is needed to prove its reliability. The microsatellite marker ORS 822 was tested to identify the Plarg gene. We conducted the research on a hybrid combination of a susceptible sunflower line of VNIIMK's breeding VK 925 and a resistant line RHA 419, a donor of the Plarg gene. We es-tablished that these lines differ from each other by the allelic state of this locus. Molecular analysis of the F1 generation showed that the microsatellite locus is inherited codominantly. We obtained the F2 generation by self-pollination and made a phytopathological evaluation of resistance to P. halstedii. Split analysis by ph-notype showed that the actually observed segregation corresponded to the theoretically expected 3:1 model for monogenic inheritance of the trait. Based on the obtained data, we determined that the Plarg gene and microsatellite locus ORS 822 are linked with a recombination frequency of 0.26. As a result of this research, we concluded that this marker can be used to select homozygous resistant sunflower plants for resistance to downy mildew in marker-assisted selection (MAS).