Benzophosphol-3-yl Triflates as Precursors of 1,3-Diarylbenzophosphole Oxides.

A simple method for the synthesis of 3-arylbenzophosphole oxides under Suzuki-Miyaura coupling conditions has been presented. It employs benzophosphol-3-yl triflate starting materials which, prior to our work, had not been used for the synthesis of 3-arylbenzophosphole oxides. The reactions proceed over 24 h and provide a library of 3-arylbenzophosphole oxides. The synthetic access to the benzophosphol-3-yl triflates has been improved. The preliminary photophysical properties of some 3-arylbenzophosphole oxides have been investigated by absorption and emission measurements. The theoretical calculations were performed to establish structure-property relationships.

Utilizing Genomics to Characterize the Common Oat Gene Pool-The Story of More Than a Century of Polish Breeding.

This study was undertaken to investigate the diversity and population structure of 487 oat accessions, including breeding lines from the ongoing programs of the three largest Polish breeding companies, along with modern and historical Polish and foreign cultivars. The analysis was based on 7411 DArTseq-derived SNPs distributed among three sub-genomes (A, C, and D). The heterogeneity of the studied material was very low, as only cultivars and advanced breeding lines were examined. Principal component analysis (PCA), principal coordinate analysis (PCoA), and cluster and STRUCTURE analyses found congruent results, which show that most of the examined cultivars and materials from Polish breeding programs formed major gene pools, that only some accessions derived from Strzelce Plant Breeding, and that foreign cultivars were outside of the main group. During the 120 year oat breeding process, only 67 alleles from the old gene pool were lost and replaced by 67 new alleles. The obtained results indicate that no erosion of genetic diversity was observed within the Polish native oat gene pool. Moreover, current oat breeding programs have introduced 673 new alleles into the gene pool relative to historical cultivars. The analysis also showed that most of the changes in relation to historical cultivars occurred within the A sub-genome with emphasis on chromosome 6A. The targeted changes were the rarest in the C sub-genome. This study showed that Polish oat breeding based mainly on traditional breeding methods-although focused on improving traits typical to this crop, i.e., enhancing the grain yield and quality and improving adaptability-did not significantly narrow the oat gene pool and in fact produced cultivars that are not only competitive in the European market but are also reservoirs of new alleles that were not found in the analyzed foreign materials.

Microfiltration Membranes Modified with Zinc by Plasma Treatment.

Polymer membranes play an important role in various filtration processes. The modification of a polyamide membrane surface by one-component Zn and ZnO coatings and two-component Zn/ZnO coatings is presented in this work. The technological parameters of the Magnetron Sputtering-Physical Vapor Deposition method (MS-PVD) for the coatings deposition process show an impact on the influence on the membrane's surface structure, chemical composition, and functional properties. The characterization of surface structure and morphology were analyzed by scanning electron microscopy. In addition, surface roughness and wettability measurements were also made. For checking the antibacterial activity, the two representative strains of bacteria Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive) were used. The filtration tests showed that polyamide membranes covered with three types of coatings, one-component Zn coatings, ZnO coatings, and two-component Zn/ZnO coatings, presented similar properties. The obtained results show that using the MS-PVD method for modification of the membrane's surface is a very promising perspective in the prevention of biofouling.

Evaluation of the Fracture Toughness KIc for Selected Magnetron Sputtering Coatings by Using the Laugier Model.

Nanoindentation is one of the methods that allows for determining the fracture properties of brittle materials. In this article, the authors present the possibility of the fracture toughness coefficient calculation of ceramic-based coatings doped by metal (W, Cr) by using the nanoindentation method with the Berkovich diamond indenter. The mechanical properties of selected coatings, such as hardness and Young's modulus, were investigated from nanohardness experiments. We analyzed the brittle fracture, which includes changes in hardness (H), Young's modulus (E), plasticity index H/E and resistance to plastic deformation H3/E2, enabled the concentration of tungsten and chromium. Due to the size of the indentation and the size of the initial cracks, it is necessary to use Scanning Electron Microscopy (SEM) to observe and measure the indentations made and the generated cracks. For evaluation of the fracture toughness in mode I, the Laugier model was chosen experimentally. The fracture toughness analysis showed that doping with concentrations of 10% W and 10% Cr causes an increase in the fracture toughness for KIc = 4.98 for TiBW (10%) and KIc = 6.23 for TiBCr (10%).

Reference genes expression stability in Avena sativa L. during compatible and incompatible interactions with Puccinia graminis.

A reliable qPCR experiment requires the selection of reference genes with a stable level of expression in a given experimental system. This study attempts to determine the reference genes (RGs) for the A. sativa-P. graminis experimental setup. We evaluated nine candidate reference genes in A. sativa (oat line Pg4 and the cultivar Kasztan) during compatible and incompatible interactions with different pathotypes of Puccinia graminis f. sp. avenae in six time points post-inoculation. The identification of genes with high expression stability was performed by four algorithms (geNorm, NormFinder, BestKeeper and ΔCt method). We found that the most appropriate combination of RGs for RT-qPCR data normalization were HNR (heterogeneous nuclear ribonucleoprotein 27C) + EF1A (elongation factor 1-alpha) + EIF4A (eukaryotic initiation factor 4A-3). The worst candidates for normalization in this dataset were CYP (cyclophilin) and TUA (alpha tubulin). Identified reference genes are suitable candidates for the standardization of gene expression studies in the A. sativa-P. graminis interaction system and potentially other related pathogens. To date, this is the first report of RGs selection in this pathosystem.

Validation of reference genes as an internal control for studying Avena sativa-Puccinia coronata interaction by RT-qPCR.

In this study we evaluated eleven candidate reference genes in Avena sativa during compatible and incompatible interactions with two different pathotypes of Puccinia coronata f. sp. avenae in six time points post-inoculation. The identification of genes with high expression stability was performed by four algorithms (geNorm, NormFinder, BestKeeper and ΔCt method). The results obtained confirmed that the combination of two genes would be sufficient for reliable normalization of the expression data. In general, the most stable in the tested plant-pathogen system were HNR (heterogeneous nuclear ribonucleoprotein 27C) and EF1A (elongation factor 1-alpha). ARF (ADP-ribosylation factor) and EIF4A (eukaryotic initiation factor 4A-3) could also be considered as exhibiting high expression stability. CYP (cyclophilin) was shown by all assessment methods to be the worst candidate for normalization in this dataset. To date, this is the first report of reference genes selection in A. sativa-P. coronata interaction system. Identified reference genes enable reliable and comprehensive RT-qPCR analysis of oat gene expression in response to crown rust infection. Understanding the molecular mechanisms involved in the host-pathogen interactions may expand knowledge of durable resistance strategies beneficial to modern oat breeding.

New Borane-Protected Derivatives of α-Aminophosphonous Acid as Anti-Osteosarcoma Agents: ADME Analysis and Molecular Modeling, In Vitro Studies on Anti-Cancer Activities, and NEP Inhibition as a Possible Mechanism of Anti-Proliferative Activity.

Many organophosphorus compounds (OPs), especially various α-aminophosphonates, exhibit anti-cancer activities. They act, among others, as inhibitors of the proteases implicated in cancerogenesis. Thesetypes of inhibitors weredescribed, e.g., for neutral endopeptidase (NEP) expressed in different cancer cells, including osteosarcoma (OS). The aim of the present study isto evaluate new borane-protected derivatives of phosphonous acid (compounds 1-7) in terms of their drug-likeness properties, anti-osteosarcoma activities in vitro (against HOS and Saos-2 cells), and use as potential NEP inhibitors. The results revealed that all tested compounds exhibited the physicochemical and ADME properties typical for small-molecule drugs. However, compound 4 did not show capability of blood-brain barrier penetration (Lipinski and Veber rules;SwissAdme tool). Moreover, the α-aminophosphonite-boranes (compounds 4-7) exhibited stronger anti-proliferative activity against OS cells than the other phosphonous acid-borane derivatives (compounds 1-3),especially regarding HOS cells (MTT assay). The most promising compounds 4 and 6 induced apoptosis through the activation of caspase 3 and/or cell cycle arrest at the G2 phase (flow cytometry). Compound 4 inhibited the migration and invasiveness of highly aggressive HOS cells (wound/transwell and BME-coated transwell assays, respectively). Additionally, compound 4 and, to a lesser extent, compound 6 inhibited NEP activity (fluorometric assay). This activity of compound 4 was involved in its anti-proliferative potential (BrdU assay). The present study shows that compound 4 can be considered a potential anti-osteosarcoma agent and a scaffold for the development of new NEP inhibitors.

Discovery and Chromosomal Location a Highly Effective Oat Crown Rust Resistance Gene Pc50-5.

Crown rust, caused by Puccinia coronata f. sp. avenae, is one of the most destructive fungal diseases of oat worldwide. Growing disease-resistant oat cultivars is the preferred method of preventing the spread of rust and potential epidemics. The object of the study was Pc50-5, a race-specific seedling crown rust resistant gene, highly effective at all growth stages, selected from the differential line Pc50 (Avena sterilis L. CW 486-1 × Pendek). A comparison of crown rust reaction as well as an allelism test showed the distinctiveness of Pc50-5, whereas the proportions of phenotypes in segregating populations derived from a cross with two crown rust-susceptible Polish oat cultivars, Kasztan × Pc50-5 and Bingo × Pc50-5, confirmed monogenic inheritance of the gene, indicating its usefulness in oat breeding programs. Effective gene introgression depends on reliable gene identification in the early stages of plant development; thus, the aim of the study was to develop molecular markers that are tightly linked to Pc50-5. Segregating populations of Kasztan × Pc50-5 were genotyped using DArTseq technology based on next-generation Illumina short-read sequencing. Markers associated with Pc50-5 were located on chromosome 6A of the current version of the oat reference genome (Avena sativa OT3098 v2, PepsiCo) in the region between 434,234,214 and 440,149,046 bp and subsequently converted to PCR-based SCAR (sequence-characterized amplified region) markers. Furthermore, 5426978_SCAR and 24031809_SCAR co-segregated with the Pc50-5 resistance allele and were mapped to the partial linkage group at 0.6 and 4.0 cM, respectively. The co-dominant 58163643_SCAR marker was the best diagnostic and it was located closest to Pc50-5 at 0.1 cM. The newly discovered, very strong monogenic crown rust resistance may be useful for oat improvement. DArTseq sequences converted into specific PCR markers will be a valuable tool for marker-assisted selection in breeding programs.

Ring Opening of Triflates Derived from Benzophospholan-3-one Oxides by Aryl Grignard Reagents as a Route to 2-Ethynylphenyl(diaryl)phosphine Oxides.

A new simple method for the synthesis of 2-ethynylphenyl(diaryl)phosphine oxides via ring opening of benzophosphol-3-yl triflates has been developed. This process occurs via nucleophilic attack of a Grignard reagent at the phosphorus center, which results in ring opening and cleavage of a leaving group. The reaction proceeds under mild conditions and, within 15-60 min, leads to a library of previously unavailable 2-ethynylphenylphosphine oxides in yields up to 98%.

Influence of Deposition Parameters of TiO2 + CuO Coating on the Membranes Surface Used in the Filtration Process of Dairy Wastewater on Their Functional Properties.

A novel approach of the deposition of two-component coating consisting of TiO2 and CuO on polymer membranes by MS-PVD method was presented in this work. This confirmed the possibility of using thin functional coatings for the modification of polymer membranes. The influence of technological parameters of the coating deposition on the membrane's structure, chemical composition and functional properties (hydrophilic, photocatalytic and bactericidal properties) were analyzed using SEM. Model microorganism such as Escherichia coli and Bacillus subtilis have been used to check the antibacterial properties. The results indicated that doping with CuO highlights the potential of bactericidal efficiency. The surface properties of the membranes were evaluated with the surface free energy. For evaluating photocatalytic properties, the UV and visible light were used. The filtration tests showed that polymer membranes treated with two-component TiO2 + CuO coatings have a permeate flux similar to the reference material (non-coated membrane). The obtained results constitute a very promising perspective of the potential application of magnetron sputtering for deposition of TiO2 + CuO coatings in the prevention of biofouling resulted from the membrane filtration of dairy wastewater.

Virulence Structure of Puccinia coronata f. sp. avenae and Effectiveness of Pc Resistance Genes in Poland During 2017-2019.

Crown rust caused by Puccinia coronata f. sp. avenae is one of the most destructive diseases of oat, regularly occurring worldwide and leading to significant yield losses. This article characterizes the pathotype structure of P. coronata in Poland and evaluates the potential of crown rust race-specific resistance genes for use in practical breeding conditions in this region. A total of 466 isolates were derived from four locations of intensive oat breeding in Poland in 2017 to 2019, representing P. coronata populations from West, East, South, and Central Poland. Their virulence structure was determined on 35 Pc differential lines in laboratory conditions. In each year and location, high pathotype diversity was observed. In total, 347 (75%) pathotypes were detected. On average P. coronata isolates collected in 2017 and 2018 were virulent to 11% of the oat differentials. In 2019 isolates from East and South of Poland were able to overcome 18.3 and 18.5% of the oat differentials, respectively. There was no isolate virulent against Pc51, Pc52, and Pc91 crown rust resistance genes. P. coronata isolates displayed modest virulence levels, high diversity, and no prevailing pathotype. The information provided here may be helpful for development of resistance breeding strategies and in choosing the most effective major genes for pyramiding into cultivars.

Genetic diversity and population structure of endangered plant species Anagallis foemina Mill. [Lysimachia foemina (Mill.) U. Manns & Anderb.].

Anagallis foemina L. [syn. Lysimachia foemina (Mill.) U. Manns & Anderb.] is an annual, segetal weed from the family Primulaceae, recognized as a very rare and endangered species in many European countries. The rare occurrence of this species is associated with the specificity of the habitats in which it occurs. Knowledge of genetic diversity within and between rare species populations is a crucial step for investigating the causes of extinction as well as developing effective conservation strategies. The current study undertakes the assessment of the genetic variation and population structure of Anagallis foemina L. specimens collected in south-eastern Poland, Volhynian Polesie and West Volhynian Upland based on inter-simple sequence repeats (ISSR) polymorphism. Twenty ISSR primers amplified 374 DNA fragments, of which 79% were polymorphic. The polymorphic information content values ranged from 0.230 to 0.430 with an average of 0.344. An average genetic similarity calculated based on Dice algorithm between all analysed samples was 0.635 (0.28-1.00). The AMOVA study found a significant difference (Φpt = 0.88, P = 0.001) between Anagallis L. genotypes gathered in Volhynian Polesie (VP) and West Volhynian Upland (VU). Analysis indicated, that 89% of the variation existed among groups and 11% within groups. UPGMA analyses grouped A. foemina samples into 2 clearly separated clusters. The plants of the same geographic origin were grouped together. Principal coordinates analysis (PCoA) as well as STRUCTURE also grouped samples in consistence with the collection site, indicating close genetic affinity of plants from the same location. The observed results are typical for fragmented and isolated populations of rare species. Isolation of a small population leads to a decrease in internal genetic variation and to an increase of variation among them. In that case, the conservation of populations from each regional cluster is important to preserve biodiversity.

Microfiltration Membranes Modified with Silver Oxide by Plasma Treatment.

Microfiltration (MF) membranes have been widely used for the separation and concentration of various components in food processing, biotechnology and wastewater treatment. The deposition of components from the feed solution and accumulation of bacteria on the surface and in the membrane matrix greatly reduce the effectiveness of MF. This is due to a decrease in the separation efficiency of the membrane, which contributes to a significant increase in operating costs and the cost of exploitative parts. In recent years, significant interest has arisen in the field of membrane modifications to make their surfaces resistant to the deposition of components from the feed solution and the accumulation of bacteria. The aim of this work was to develop appropriate process parameters for the plasma surface deposition of silver oxide (AgO) on MF polyamide membranes, which enables the fabrication of filtration materials with high permeability and antibacterial properties.

Identification of molecular markers for the Pc39 gene conferring resistance to crown rust in oat.

KEY MESSAGE: Six new PCR-based markers for the Pc39 crown rust resistance gene in Avena sativa L. were developed. Pc39 was mapped to Mrg11 of the oat consensus map using BLASTn analysis. The aim of this study was the identification of molecular markers for the Pc39 gene in cultivated oat (Avena sativa L.). Pc39 is a major race-specific crown rust resistance gene originally found in an Israeli accession of the wild hexaploid Avena sterilis. The effectiveness of this gene in Europe has decreased in recent years, but is still relatively high and breeding programs would benefit from the availability of molecular markers to aid in its mapping and deployment. The complexity of the oat genome poses a significant obstacle to genetic research. No oat rust resistance genes have yet been cloned, and even the number of relevant molecular markers is very limited. Here, genotyping of a segregating population derived from a cross 'Celer' (Pc39)/STH9210 (susceptible) was conducted using RAPD- and SRAP-PCR-based methods, as well as microarray-based DArT™ and next-generation sequencing DArTseq™ techniques. Markers associated with Pc39 were placed on the hexaploid oat consensus linkage group Mrg11 at 3.7-6.7 cM. Six new PCR-based markers were developed to allow identification of the resistant Pc39 allele. These tightly linked markers will be useful in marker-assisted selection, with the closest, SCAR_3456624, being within 0.37 cM of Pc39. The newly developed markers could find applications in the fine mapping or positional cloning of this gene. Moreover, easy-to-use PCR-based markers linked to Pc39 could facilitate the utilization of this gene in oat breeding programs, especially as a component of crown rust resistance gene pyramids.

Microfiltration Membranes Modified with Composition of Titanium Oxide and Silver Oxide by Magnetron Sputtering.

In this work, the authors present the possibility of modification of polymer membranes by TiO2 + AgO coating created by the magnetron sputtering method. The two-component TiO2 + AgO coating can improve and shape new functional properties such as bactericidal and photocatalytic properties. The influence of magnetron power changes on the structure of the membrane was investigated as well. The structure and elemental composition of TiO2 + AgO coatings were analyzed using SEM and EDS technique. All deposited coatings caused a total inhibition of the growth of two investigated colonies of Escherichia coli and Bacillus subtilis on the surface. The photocatalytic properties for membranes covered with oxide coatings were tested under UV irradiation and visible light. The filtration result show that polymer membranes covered with two-component TiO2 + AgO coatings have a permeate flux similar to the non-coated membranes.

Virulence Structure and Diversity of Puccinia coronata f. sp. avenae P. Syd. & Syd. in Poland During 2013 to 2015.

The crown rust fungus Puccinia coronata f. sp. avenae P. Syd. & Syd. (Pca) attacks cultivated oat and its wild relatives, causing significant losses to the crop worldwide. Although understanding the origin and dynamics of the pathogen's diversity is critical to developing methods for its control, there are little relevant data on Pca virulence diversity in Europe, the global center of oat production. The goal of this study was to analyze the diversity of Pca populations in Poland in 2013 to 2015 based on their ability to overcome currently available host resistance Pc genes. Pca isolate virulence was evaluated on a panel of lines containing 26 major resistance genes of oat. The isolates were able to overcome from 1 to 16 resistance genes each, with most isolates being virulent on five to seven lines. In all years, a very high level of crown rust pathotype diversity was observed, with Simpson and Evenness indices of 0.99. In total, 156 different pathotypes were detected, with no prevalent pathotype in any of the 3 years analyzed. The results showed that the virulence level of P. coronata isolates was relatively low for each year studied (21% on average), most likely owing to the low take up of Pc genes in Polish oat cultivars, meaning that many sources of resistance are still effective against Pca races occurring in Poland. The long-range dispersal of Puccinia spores supported by the availability of wild, weedy, and cultivated Avena species makes it likely that the virulence profile seen in Poland is representative of much of central Europe and beyond.

Detached Leaf Assays for Resistance to Crown Rust Reveal Diversity Within Populations of Avena sterilis.

Crown rust is the most widespread and damaging disease of oat (Avena species). Genetic resistance to the pathogen is the preferred method for crop protection but widespread deployment of limited numbers of major effect genes has promoted the rapid emergence and spread of pathogen races that are able to overcome these genes. Combining genes with even partial resistance may help develop durable cultivars that are less vulnerable to changes in pathogen virulence. Partial resistance is expected to be relatively common in populations of wild species where constant pathogen pressure encourages diversity in host resistance mechanisms, but it may be discarded in conventional screens for major gene resistance. Here, we used a detached leaf assay to detect resistance to the crown rust pathogen, Puccinia coronata Cda. f. sp. avenae, in previously uncharacterized collections of the hexaploid wild oat relative A. sterilis made by the Polish National Centre for Plant Genetic Resources. Many of the accessions were collected in Morocco, the center of diversity for the Avena genus. The detached leaf assessment allowed individual plants to be challenged with multiple pathotypes and their responses compared with 34 known differentials. Broad-spectrum resistance was identified within accession PL 51855, which behaved as a single major locus on crossing to three cultivars. The locus provided resistance to over 50 rust pathotypes, a greater range than seen for any of the known host resistance (Pc) genes. Strong resistance was identified in other accessions, and heterogeneity in response within accessions was common. Several accessions show multiple partial resistance responses that may be of value for developing durable resistance in cultivars. Because the sources of resistance in all but two differential lines were collected outside of Morocco, resistance in all accessions tested here are potentially novel. This study demonstrates that diversity within A. sterilis accessions collected in Morocco could be a very valuable source of resistance to crown rust, and it provides new germplasm for use in resistance breeding programs. Detached leaf assessment provides a valuable first step in the identification of promising candidates in complex gene bank accessions.

Characteristics of Resistance to Puccinia coronata f. sp. avenae in Avena fatua.

Crown rust, caused by Puccinia coronata f. sp. avenae, is the most widespread and harmful fungal disease of oat. The best defense against the pathogen is use of cultivars with genetic resistance, which is effective, economic, and an environmentally friendly alternative to chemical control. However, the continuous evolution of the pathogen can rapidly overcome major gene resistance, creating an urgent need to identify new sources. Wild oat accessions have already proven to be valuable donors of many resistance genes, but the weed species Avena fatua remains underexploited. Its abundance across multiple environments and the frequent occurrence of herbicide-resistant populations demonstrate its ready ability to adapt to biotic and abiotic stresses; yet, surprisingly, there are no extensive studies which describe crown rust resistance occurrence in gene bank stocks of A. fatua. In this study, 204 accessions of A. fatua maintained in the collections of the United States Department of Agriculture (USDA) and Polish National Centre for Plant Genetic Resources were evaluated at the seedling stage for crown rust reaction using host-pathogen tests with five highly diverse and virulent races of P. coronata. Of tested genotypes, 85% showed a heterogeneous infection pattern, while 61% were susceptible or moderately susceptible to all races. Of the 79 resistant A. fatua accessions, seedling resistance to at least two P. coronata isolates was recognized within 19 accessions, with 13 displaying a homogeneously resistant phenotype to one or two races. Accessions showing multiple single seedling resistance to three or four isolates were observed. Based on the seedling reaction to isolates used in the study, 18 infection profiles (IP) were determined. Using UPGMA clustering, resistant accessions were divided into six main clusters encompassing samples with similar IPs. Twelve of 18 patterns allowed us to postulate the likely presence of novel crown rust resistance genes, whose origin was predominantly from Kenya or Egypt. Future work will clarify the genetic basis of the resistances observed here, as well as confirm their potential utility in breeding resistant oat cultivars.

Resistance to Puccinia coronata f. sp. avenae in Avena magna, A. murphyi, and A. insularis.

Wild oat tetraploids of the section Pachycarpa have already been proven to be a rich source of useful genes but have largely been unexploited for Puccinia coronata resistance. In this study, accessions of Avena magna, A. murphyi, and A. insularis gathered from European and North American gene banks were evaluated at the seedling stage for crown rust reaction using the host-pathogen test and six highly diverse and virulent P. coronata isolates. Of the 92 Avena accessions analyzed, 58.7% were resistant to at least one crown rust race. In all, 37% of the tested accessions reacted nonuniformly, which indicated their heterogeneity. The highest level of resistance was observed in three of the accessions, one of which was verified by flow cytometry as being hexaploid and two of which were verified as being tetraploids. The infection profiles of 19 accessions corresponded to resistance determined by the genes Pc14, Pc39, Pc40, Pc48, Pc50, Pc54, Pc55, Pc61, Pc67, Pc68, Pc97, Pc101, or Pc104. The patterns of infection of the remaining resistant A. magna and A. murphyi accessions allowed us to postulate the presence of potentially novel crown rust resistance genes.

Avena sterilis L. Genotypes as a Potential Source of Resistance to Oat Powdery Mildew.

The aim of the present study was to identify Avena sterilis genotypes demonstrating a high level of resistance against oat powdery mildew, using host-pathogen tests. The study was conducted on 350 A. sterilis genotypes from different parts of the world. Six single-spore isolates of Blumeria graminis (DC.) f. sp. avenae, which demonstrated different levels of virulence to control lines and cultivars, were used in host-pathogen screening tests. To confirm the resistant response of selected genotypes, 13 other isolates were used. Reactions to the isolates were grouped into three classes: resistant, intermediate, and susceptible. Susceptible cultivars Sam and Fuchs were used as controls to estimate the degree of infection. The results of the screening test showed that 10 genotypes were classified as resistant. The second test based on 13 other isolates revealed that only four of the 10 genotypes were a valuable source of resistance against powdery mildew. The identified genotypes may be used in oat breeding programs to increase the level of resistance against powdery mildew. First, however, further studies aimed at identifying whether this resistance is conditioned by a single gene or combinations of different genes are required.