Blumeria Research Articles

Powdery mildew resistance of barley accessions from Dagestan.

Powdery mildew caused by the parasitic fungus Blumeria graminis (DC.) Golovin ex Speer f. sp. hordei Marchal is one of the most common diseases of barley. Growing resistant varieties can signif icantly minimize harmful effects of the pathogen. The specif icity in the interaction between the fungus and its host plant requires a continuous search for new donors of the resistance trait. The powdery mildew resistance of 264 barley accessions from Dagestan and genetic control of the trait in resistant forms were studied under f ield and laboratory conditions. Forty-seven barley lines carrying previously identif ied powdery mildew resistance genes were also examined. During three years, the experimental material was evaluated under severe infection pressure at the Dagestan Experiment Station of VIR (North Caucasus, Derbent). Juvenile resistance against the Northwest (St. Petersburg, Pushkin) pathogen population was evaluated in a climatic chamber. The genetic control of B. graminis resistance in the selected accessions was studied with the application of hybridological and molecular analyses. The level of genetic diversity of Dagestan barley for effective resistance to powdery mildew is very low. Only two accessions, VIR-23787 and VIR-28212, are resistant against B. graminis at both seedling and adult plant stages. The high-level resistance of breeding line VIR-28212 originating from barley landrace VIR-17554 (Ep-80 Abyssinien) from Ethiopia is controlled by the recessive gene mlo11. Accession VIR-17554 is heterogeneous for the studied trait, with the powdery mildew resistant genotypes belonging to two varieties, dupliatrum (an awnless phenotype) and nigrinudum (an awned phenotype). In accession VIR-23787, a recessive resistance gene distinct from the mlo11 allele was identif ied. This accession is supposed to be protected by a new, effective pathogen resistance gene.

The activation of wheat resistance against powdery mildew by combination of biotic elicitor and NO donor

Aim. The aim of research was to analyze the activation of Triticum aestivum L. non-specific resistance by the effect of ferulic acid and NO on H2O2 content against fungal pathogen from environment in field trials. Methods. Content of endogenous H2O2 was measured in elicitor treated and infected wheat plants (cv. Oberig myronivskij and Svitanok myronivskij) during different ontogenesis phases. The extent of disease development, morphometric parameters and yield structure were analyzed. Results. The data obtained suggest that different levels of endogenous hydrogen peroxide were induced in wheat leaves by treatment. The growth and yield were stimulated. The infection damage decreased. Conclusions. The role of endogenous hydrogen peroxide is crucial for wheat defense during all vegetation period. The elicitor and donor NO induced effective defense responses and resistance in winter wheat against Erysiphe graminis.
 Keywords: Triticum aestivum L., ferulic acid, NO, induced resistance, powdery mildew.

Powdery Mildew Resistance Phenotypes of Wheat Gene Bank Accessions.

Simple SummaryBread wheat is one of the most important sources of human and animal food and powdery mildew is a serious disease of this crop. Breeding and growing resistant cultivars are an effective and environmentally friendly way of reducing the adverse impact of the disease on grain yield and quality. The main aim of this study was to detect major resistances against powdery mildew in a set of wheat accessions from the Czech gene bank and to group them according to their responses. Ear progenies of 448 varieties originating from 33 countries were inoculated with three isolates of the pathogen. One hundred and ten varieties showed resistance to at least one isolate and 59 varieties were resistant to all three isolates. Resistance to the three isolates was present mostly in varieties of Northwest Europe and was more than three times more frequent in spring than in winter wheats. Results will facilitate a rational and practical approach of breeding new wheat cultivars using this set of gene bank accessions as recipients of novel genes from wheat-related species and accumulate minor resistance genes to improve resistance durability.Powdery mildew (Blumeria graminis f. sp. tritici) is a common pathogen of bread wheat (Triticum aestivum L.), and genetic resistance is an effective and environmentally friendly method to reduce its adverse impact. The introgression of novel genes from wheat progenitors and related species can increase the diversity of disease resistance and accumulation of minor genes to improve the crop’s resistance durability. To accomplish these two actions, host genotypes without major resistances should be preferably used. Therefore, the main aim of this study was to carry out seedling tests to detect such resistances in a set of wheat accessions from the Czech gene bank and to group the cultivars according to their phenotype. Ear progenies of 448 selected cultivars originating from 33 countries were inoculated with three isolates of the pathogen. Twenty-eight cultivars were heterogeneous, and 110 cultivars showed resistance to at least one isolate. Fifty-nine cultivars, mostly from Northwest Europe, were resistant to all three isolates were more than three times more frequently recorded in spring than in winter cultivars. Results will facilitate a rational and practical approach preferably using the set of cultivars without major resistances for both mentioned methods of breeding wheat cultivars resistant to powdery mildew.

RACE1, a Japanese Blumeria graminis f. sp. hordei isolate, is capable of overcoming partially mlo-mediated penetration resistance in barley in an allele-specific manner.

Loss-of-function mutation of the MILDEW RESISTANCE LOCUS O (Mlo) gene confers durable and broad-spectrum resistance to powdery mildew fungi in various plants, including barley. In combination with the intracellular nucleotide-binding domain and leucine-rich repeat receptor (NLR) genes, which confer the race-specific resistance, the mlo alleles have long been used in barley breeding as genetic resources that confer robust non-race-specific resistance. However, a Japanese Blumeria graminis f. sp. hordei isolate, RACE1, has been reported to have the potential to overcome partially the mlo-mediated penetration resistance, although this is yet uncertain because the putative effects of NLR genes in the tested accessions have not been ruled out. In this study, we examined the reproducibility of the earlier report and found that the infectious ability of RACE1, which partially overcomes the mlo-mediated resistance, is only exerted in the absence of NLR genes recognizing RACE1. Furthermore, using the transient-induced gene silencing technique, we demonstrated that RACE1 can partially overcome the resistance in the host cells with suppressed MLO expression but not in plants possessing the null mutant allele mlo-5.

Changes in Photosynthesis Could Provide Important Insight into the Interaction between Wheat and Fungal Pathogens

Photosynthesis is a universal process for plant survival, and immune defense is also a key process in adapting to the growth environment. Various studies have indicated that these two processes are interconnected in a complex network. Photosynthesis can influence signaling pathways and provide both materials and energy for immune defense, while the immune defense process can also have feedback effects on photosynthesis. Pathogen infection inevitably leads to changes in photosynthesis parameters, including Pn, Gs, and Ci; biochemical materials such as SOD and CAT; signaling molecules such as H2O2 and hormones; and the expression of genes involved in photosynthesis. Some researchers have found that changes in photosynthesis activity are related to the resistance level of the host, the duration after infection, and the infection position (photosynthetic source or sink). Interactions between wheat and the main fungal pathogens, such as Puccinia striiformis, Blumeria graminis, and Fusarium graminearum, constitute an ideal study system to elucidate the relationship between changes in host photosynthesis and resistance levels, based on the accessibility of methods for artificially controlling infection and detecting changes in photosynthesis, the presence of multiple pathogens infecting different positions, and the abundance of host materials with various resistance levels. This review is written only from the perspective of plant pathologists, and after providing an overview of the available data, we generally found that changes in photosynthesis in the early stage of pathogen infection could be a causal factor influencing acquired resistance, while those in the late stage could be the result of resistance formation.

Mlo Resistance to Powdery Mildew (Blumeria graminis f. sp. hordei) in Barley Landraces Collected in Yemen

Barley (Hordeumvulgare L.) is one of the most important cereal crops in the world. Powdery mildew on barley, which is caused by the pathogen Blumeria graminis f. sp. hordei, occurs world-wide and can result in severe yield loss. Thousands of barley accessions are stored in national gene banks, and their characterization for breeding purposes is needed. This study was conducted to determine the resistance to powdery mildew in 33 barley landraces from Yemen, which were obtained from the ICARDA gene bank. Twenty differential isolates of barley powdery mildew were used. Nine single plant lines were selected from five landraces, based on tests that were performed with 30 plants per landrace, after inoculation with the most avirulent isolate of barley powdery mildew available. Two of these landraces originated from the Al Bayda province in Yemen, and three others originated from Dhamar, Sanaa, and Taizz, respectively. Next, single plant lines were tested using a set of 20 differential isolates of powdery mildew. Two lines that were selected from landrace from the Al Bayda province in Yemen, showed disease reaction designated as 0(4), which is specific for the presence of Mlo resistance. The new source of highly effective Mlo powdery mildew resistance that is described in this study could be used in barley breeding programs.

Design, Synthesis, and Evaluation of Novel Isothiazole-Purines as a Pyruvate Kinase-Based Fungicidal Lead Compound

Target identification is one of the most important bases for novel pesticide development; pyruvate kinase (PK) was discovered as a potent fungicide target in our previous studies. To continue the PK-based fungicide development, novel isothiazole-purine derivatives were rationally designed and synthesized. Bioassay results showed that compound 5ai displayed excellent in vitro activity against Rhizoctonia solani with an EC50 of 1.5 μg/mL, which was superior to those of positive controls diflumetorim with its EC50 of 19.8 μg/mL and PK-based lead YZK-C22 with its EC50 of 4.2 μg/mL. Compounds 3b (5.2 μg/mL) and 3c (4.5 μg/mL) displayed better activities against Gibberella zeae with their EC50s falling between 4.0 and 5.5 μg/mL, while YZK-C22 showed an EC50 of 6.4 μg/mL. In addition, 5ah exhibited promising in vivo activity against Erysiphe graminis and Puccinia sorghi Schw. with 100% efficacy at 10 μg/mL and 90% efficacy at 2 μg/mL against P. sorghi Schw. Compound 5ai showed good PK inhibitory activity with an IC50 of 38.8 μmol/L, and it was well docked into the active site of the target enzyme PK, which was slightly more active than YZK-C22 with its IC50 of 42.4 μmol/L. Our studies discovered that isothiazole-purines were PK-based fungicidal leads deserving of further study.

The Plant Salicylic Acid Signalling Pathway Regulates the Infection of a Biotrophic Pathogen in Grasses Associated with an Epichloë Endophyte.

The study of the contribution of the plant defence hormones, salicylic acid (SA) and jasmonic acid (JA), in the resistance against pathogens of plants associated with Epichloë fungal endophytes has been scanty. We hypothesised that Epichloë spp., capable of inducing host plant SA-dependent defences, would increase the levels of plant resistance against biotrophic pathogens. Plants of Achnatherum inebrians, with and without the fungal endophyte Epichloë gansuensis, were inoculated with the biotrophic fungal pathogen Blumeria graminis. We measured the status of plant defences (associated with SA and JA signalling pathways) and the levels of resistance to the pathogen. Plants associated with the endophyte showed less disease symptoms caused by the biotrophic pathogen than plants without the endophyte. In agreement with our hypothesis, the Epichloë endophyte increased the plant production of SA and enhanced the expression levels of plant genes of synthesis and response to the SA hormone. The elevated expression of SA-related genes coding for putative plant enzymes with anti-fungal activities promoted by the endophyte may explain the enhanced resistance to the pathogen. The present study highlights that interaction between the plant immune system and Epichloë fungal endophytes can contribute significantly to the resistance of endophyte-symbiotic plants against pathogens.

Myronosets – a new productive and high-protein winter triticale cultivar, adapted to the woodlands/forest-steppe and forest-steppe of Ukraine

The creation of new triticale genotypes, the potential of which to a certain extent would meet scientific and production needs, will never lose its relevance.
 Purpose and objectives – to create a new productive and high-protein winter triticale cultivar, adapted to the Woodlands/Forest-Steppe and Forest-Steppe of Ukraine.
 Materials and methods. The breeding work to expend the triticale diversity was continued at the Educational and Research Center of Bila Tserkva National Agrarian University in 2007–2017. The control and environmental trials were conducted in 2009-2019 in the Woodlands (Polissya Institute of Agriculture NAAS (2007–2009); predecessor: seeded fallow), central Forest-Steppe (V.M. Remeslo Myronivska Institute of Wheat NAAS (2016–2019); forecrops: mustard, soybean, pea for seeds; Bila Tserkva NAU (2009–2016); predecessors: seeded fallow, potato), and northern Forest-Steppe (Institute of Horticulture NAAS (2016–2017); forecrop: perennial grasses). No mineral fertilizers were applied. No plant protection measures were taken. Hybridization was performed by manual emasculation of female components. Plants were pollinated by the twirl method 2–3 days after emasculation. The breeding material was studied in compliance with the guidelines of the All-Union Research Institute of Plant Breeding and the methodology of the state cultivar trials. Data were statistically processed, as B.А. Dospekhov described, using Statistica-5.5 and Excel-2003 software.
 Results and discussion. We focus on the importance of triticale for mankind both at the present and in the future. We retrospectively reviewed data on the creation of a new winter triticale cultivar, Myronosets. Bioecological features and morphological characteristics of the new cultivar are given. The grain yield and quality are also summarized. The article covers the quantitative parameters of dough and bread from Myronosets grain. We compared the yields, resistance to lodging, in-spike germination, resistance to fungal pathogens and unfavorable abiotic environmental factors in the new triticale cultivar and previously created ones.
 The data of the 2019–2020 state variety trials of Myronosets are analyzed, and they indicate that the new cultivar has a high potential in agroecosystems of the Woodlands and Forest-Steppe of Ukraine.
 Myronosets was found to be a source of the short stem (£90 cm) in subsequent hybrid generations.
 In 2008, interspecific hybridization within the notogenus × Triticosecale and double individual selection from F2–F4 hybrid populations derived from crossing (♀Avhusto x ♂Yahuar) x ♂K9844/93 followed by repeated improving selections in F10 allowed us to distinguish the best line, LCh97, which was later named as cultivar Myronosets.
 The new triticale cultivar can give > 7.5 t/ha. The average yield is 5.7 t/ha in the Forest-Steppe – Woodlands transition belt, 6.3 t/ha in the central Forest-Steppe, and 3.5 t/ha in the Woodlands. It is noticeable for high lodging resistance, high shedding resistance, low spike brashness, resistance to in-spike germination, complex resistance to Puccinia recondita f. sp. tritici Rob. ex Desm (8.5 points), Blumeria graminis (DC.) Speer (9 points.), and Fusarium graminearum Schwabe (8.5 points) and to to the pest Mayetiola destructor Say (8.5 points), high frost tolerance, high winter hardiness, and high drought resistance (8.5–9 points). About 70% of plants survive the laboratory freezing at -18.3°C. The cultivar is also resistant to spring and autumn frosts (9 points).
 Myronosets plants were revealed to be able to regulate their performance under the influence of unfavorable extreme bio- and abiotic factors, leaving 3–4 (more seldom 1–2) fruiting stems, often 1–3 stems with underdeveloped spikes and 1–2 unfertile stems without spikes, which form a radical rosette.
 Conclusions. As it was shown in the state variety trials, Myronosets is a mid-protein cultivar and recommended for cultivation in agroecosystems of the Woodlands and Forest-Steppe. Myronosets was proven to be a source of the short stem

The Exocyst Complex Subunit EXO70E1-V From Haynaldia villosa Interacts With Wheat Powdery Mildew Resistance Gene CMPG1-V.

EXO70 belongs to the exocyst complex subunit that plays a critical role in regulating plant cell polarity establishment and defense response. A previous study proved that the E3 ligase CMPG1-V from Haynaldia villosa, a diploid wheat relative, positively regulates the resistance to wheat powdery mildew (Pm), caused by fungus Blumeria graminis f.sp tritici (Bgt). In this study, a member of EXO70 superfamily named EXO70E1-V was isolated from H. villosa, and EXO70E1-V interacted with CMPG1-V were shown by yeast two-hybrid (Y2H), pull-down assay, bimolecular fluorescence complementation (BiFC) assay, and luciferase complementation imaging (LCI) assay. It is localized in various subcellular organs, i.e., plasma membrane (PM) and endoplasmic reticulum. Co-expression of EXO70E1-V and CMPG1-V showed dot-like structure fluorescence signals that were mainly in PM and nucleus. Expression of EXO70E1-V was relatively higher in leaf and was significantly induced by Bgt infection and exogenous application of hormones such as salicylic acid. Transient or stable overexpression of EXO70E1-V could not enhance/decrease the Pm resistance level, suggesting overexpression of EXO70E1-V alone has no impact on Pm resistance in wheat.

New sources of powdery mildew resistance among winter bread wheat for adjusting the breeding immunological programs in the Agricultural Research Center “Donskoy”

Systematic work on the development of winter wheat varieties possessing resistance to a complex of the most harmful diseases has been carried out in the Agricultural Research Center “Donskoy” since the early 1970s. During this period, there has been created a large number of varieties that possess resistance to 3–4 diseases in conditions of infectious backgrounds of pathogens. Due to the analysis of varieties, there was identified a small number of varieties resistant to powdery mildew. Powdery mildew, caused by the fungus Blumeria graminis (DC) Speer, annually occurs on wheat, affecting all aboveground plant organs. Earlier the FSBSI “ARC “Donskoy” developed and widely cultivated the medium-resistant varieties ‘Tanais’ (2006), ‘Nakhodka’ (2015), ‘Etyud’, ‘Shef’, ‘Lilit’ (2016), ‘Volnitsa’ (2017), ‘Polina’, Yubiley Dona’ , ‘Podarok Krymu’ (2018), ‘Niva Dona’ (2019). In recent years, breeders have developed such varieties with high resistance to the pathogen as ‘Donskaya Step’ (2016), ‘Premiera’, ‘Univer’ (2018), ‘Priazovye’, ‘Zolotoy Kolos’ (2020). But the breeding process of varieties for resistance to powdery mildew is difficult, since it is explained by the small number of effective resistance genes and their sources. Therefore, the purpose of the current study was to identify new sources of resistance to the pathogen. Under the conditions of artificial infection, during last 10 years there was conducted a testing of 302 varieties and samples of winter wheat of domestic and foreign breeding. There have not been identified immune varieties. There was identified a small percentage (15.2) of varieties that were resistant to the pathogen. Among the Russian varieties they were ‘L 3191 k-5-8’, ‘Akhmat’, ‘Alievich’, ‘Barier’, ‘Ulyasha’, ‘Knyaginya Olga’, which were not attacked by the disease over the years of testing. Among foreign varieties, the varieties ‘Bombus’, ‘Sailor’ (France), ‘Etana’, ‘Rotax’, ‘KVS-Emil’ (Germany), ‘Fidelius’ (Austria), ‘MV 09-04’ (Hungary) were identified as the best ones in their resistance to powdery mildew. All identified sources of resistance have been recommended in breeding programs for immunity.

What is the role of the nitrate reductase (euknr) gene in fungi that live in nitrate-free environments? A targeted gene knock-out study in Ampelomyces mycoparasites

Mycoparasitic fungi can be utilized as biocontrol agents (BCAs) of many plant pathogens. Deciphering the molecular mechanisms of mycoparasitism may improve biocontrol efficiency. This work reports the first functional genetic studies in Ampelomyces, widespread mycoparasites and BCAs of powdery mildew fungi, and a molecular genetic toolbox for future works. The nitrate reductase (euknr) gene was targeted to reveal the biological function of nitrate assimilation in Ampelomyces. These mycoparasites live in an apparently nitrate-free environment, i.e. inside the hyphae of powdery mildew fungi that lack any nitrate uptake and assimilation system. Homologous recombination-based gene knock-out (KO) was applied to eliminate the euknr gene using Agrobacterium tumefaciens-mediated transformation. Efficient KO of euknr was confirmed by PCR, and visible phenotype caused by loss of euknr was detected on media with different nitrogen sources. Mycoparasitic ability was not affected by knocking out euknr as a tested transformant readily parasitized Blumeria graminis and Podosphaera xanthii colonies on barley and cucumber, respectively, and the rate of mycoparasitism did not differ from the wild type. These results indicate that euknr is not involved in mycoparasitism. Dissimilatory processes, involvement in nitric oxide metabolism, or other, yet undiscovered processes may explain why a functional euknr is maintained in Ampelomyces.

Inheritance of resistance of spring barley to Erysiphe graminis f. sp. hordei in F1 and variability in F2 in the conditions of the Right-Bank Forest-Steppe of Ukraine

The nature of the inheritance of resistance to Erysiphe graminis f. sp. hordei in the crosses of genotypes of spring barley in F1 and transgressive variability in F2 populations are investigated. Inheritance of the trait of resistance to Erysiphe graminis f. sp. hordei in F1, by hybridization of genotypes of spring barley with known genes of resistance to Erysiphe graminis f. sp. hordei in European varieties Eunova (mlo11) and Barke (mlo9), which are located on chromosome 1H, was positively dominated. Inheritance of the F1 trait in Aspen (mlo11) and Adonis (mlo9) cultivars was partially positive. The influence of parental pairs for hybridization on the indicators of the degree of phenotypic dominance, hypothetical and true heterosis was established. Resistance to Erysiphe graminis f. sp. hordei in F1 hybrids was observed heterosis (positive dominance) in fve hybrid combinations (hp = 1.1–1.9 %): Barke/Badoryi, Barke/Sanktrum, Parnas/Rostentsii, Badoryi/ Barke, Eunova/Zvershennia. Hypothetical heterosis (Ht) in F1 was observed in 13 of 16 hybrids (from +2.8 % to +97.6 %). A positive value of true heterosis (Htb) in F1 was observed in 15 hybrids out of 16 (from +1.9 % to +98.8 %). Inheritance of the trait of resistance to Erysiphe graminis f. sp. hordei in all studied hybrids was influenced by the cytoplasm of the mother plant, except for the hybrid Eunova / Triangel, where the influence of the nuclear apparatus was detected. Hybrids were found in the F 2 population with high resistance to Erysiphe graminis f. sp. hordei, which exceeded the parental components, which indicates a signifcant shaping process and the possibility of selection on the basis of the studied trait. The degree of positive transgression ranged from 16.0 % to 73.0 % in hybrids Aspen / Skarlet, Adonis / Vanja, Barke / Badoryi, Barke / Sanktrum, Eunova / Triangel and Eunova / Zvershennia, where highly resistant varieties were used for the mother form. The combinations in which the frequency of transgression was observed in more than 50.0 % of plants are hybrids: Eunova / Triangel, Barke / Sanktrum, Eunova / Zvershennia, Parnas / Rostentsii and Barke / Badoryi. Key words: spring barley, resistance, Erysiphe graminis f. sp. hordei, combinations of crossing, inheritance, F1, true and hypothetical heterosis, degree of phenotypic dominance, F 2, degree and frequency of transgressions.

Effect of flutianil on the morphology and gene expression of powdery mildew.

Flutianil, a fungicide effective only on powdery mildew, was previously reported to affect the host cell's haustorial formation and nutrient absorption. Studies were conducted to investigate flutianil's primary site of action on Blumeria graminis morphology using transmission electron microscope (TEM) observation and RNA sequencing (RAN-seq) techniques. TEM observation revealed that flutianil caused the extra-haustorial matrix and fungal cell wall to be obscured, without remarkable changes of other fungal organelles. RNA-seq analysis indicated that, unlike other powdery-mildew fungicides, flutianil did not significantly affect the constantly expressed genes for the survival of B. graminis. Genes whose expression is up- or downregulated by flutianil were found; these are the three sugar transporter genes and various effector genes, mainly expressed in haustoria. These findings indicate that the primary site of action of flutianil might be in the haustoria.

Heat Stress Pre-Exposure May Differentially Modulate Plant Defense to Powdery Mildew in a Resistant and Susceptible Barley Genotype.

Heat stress negatively affects barley production and under elevated temperatures defense responses to powdery mildew (Blumeria graminis f. sp. hordei, Bgh) are altered. Previous research has analyzed the effects of short-term (30 s to 2 h) heat stress, however, few data are available on the influence of long-term exposure to heat on powdery mildew infections. We simultaneously assessed the effects of short and long term heat pre-exposure on resistance/susceptibility of barley to Bgh, evaluating powdery mildew infection by analyzing symptoms and Bgh biomass with RT-qPCR in barley plants pre-exposed to high temperatures (28 and 35 °C from 30 s to 5 days). Plant defense gene expression after heat stress pre-exposure and inoculation was also monitored. Our results show that prolonged heat stress (24, 48 and 120 h) further enhanced Bgh susceptibility in a susceptible barley line (MvHV118-17), while a resistant line (MvHV07-17) retained its pathogen resistance. Furthermore, prolonged heat stress significantly repressed the expression of several defense-related genes (BAX inhibitor-1, Pathogenesis related-1b and Respiratory burst oxidase homologue F2) in both resistant and susceptible barley lines. Remarkably, heat-suppressed defense gene expression returned to normal levels only in MvHV07-17, a possible reason why this barley line retains Bgh resistance even at high temperatures.

Screening and Evaluation of Wheat Varieties against Powdery Mildew (Blumeria graminis f. sp. tritici) under field Conditions

The powdery mildew fungi ( Blumeria graminis) continue to rank among the most harmful pathogens on wheat ( Triticum aestivum L.) in the world . It is becoming a disease of concern in the North Western Plains Zone, Northern Hills Zone and Southern Hills Zone of the country. Twenty six varieties of wheat were tested against powdery mildew pathogen for screening of resistant or moderately susceptible or susceptible ones. The experiment was conducted in randomized complete block with three replications. The plants were inoculated in evening with spore suspension of the pathogen. The wheat seedlings were inoculated at 25-30 days after planting which is the most vulnerable period of susceptibility. Normal agricultural practices including recommended fertilizer dose and irrigation schedule were followed. Infection types and powdery mildew severity were recorded for each of the tested variety. A wide range of reactions from resistant to highly susceptible were shown by wheat varieties whereas no any variety showed immune response. Wheat varieties K1105, K1114, K1204, K1213, K1215, K1217, K1315 and K1601 were found resistant to powdery mildew showing low infection and low level of disease severity (4.5% - 24.6%).

Virulence Structure of Blumeria graminis f. sp. avenae Populations in Poland across 2014-2015.

The purpose of this study was to determine the virulence structure of oat powdery mildew (Blumeria graminis f. sp. avenae, Bga) populations in Poland collected in 2014 and 2015. Powdery mildew isolates were collected from 18 locations in Poland. In total, nine lines and cultivars of oat, with different mildew resistance genes, were used to assess virulence of 180 isolates. The results showed that a significant proportion of the Bga isolates found in Poland were virulent to differentials with Pm1, Pm3, Pm6, and Pm3 + Pm8 genes. In contrast Pm4, Pm5, Pm2, and Pm7 genes were classified as resistant to all pathogen isolates used in the experiment. Based on obtained results we can state that there are differences in virulence pattern and diversity parameters between sites and years, but clear trends are not deducible.

Emission of novel volatile biomarkers for wheat powdery mildew

Natural ecosystems including host-pathogen interactions produce a plethora of biogenic volatile organic compounds (BVOCs). Infections by phytopathogens change the volatile profile substantially and dynamically over a crop field or even on a larger scale. Despite their worldwide importance in agriculture little is known about the BVOC emissions of cereal crops, such as wheat, and their pathogens. The wheat-powdery mildew interaction is especially relevant, because powdery mildew is widespread on a global scale and is caused by an obligatory biotrophic pathogen (Blumeria graminis f.sp. tritici, Bgt). Since the BVOCs in this important fungus have still not been identified, the most frequent local natural pathotypes were studied by artificial inoculation and dynamic headspace collection followed by GC–MS analysis in three consecutive years. Of the 48 BVOCs identified in a total of 120 samples, six compounds (1,3-octadiene, 1,3-cis,5-cis-octatriene, 1-heptanol, (5Z)-octa-1,5-dien-3-ol, 1-octen-3-ol and 3-octanone) were detected only in Bgt-inoculated plants, and were hence quantitated. The latter three BVOCs were the most abundant in symptomatic plants with a characteristic distribution pattern. Additional wheat genotypes, different host plant development stages, and early and full disease progression in the presence of other pathogen mixes were also tested for the specificity of the proposed biomarkers. The three major biomarkers, namely (5Z)-octa-1,5-dien-3-ol, 1-octen-3-ol and 3-octanone were robustly applicable for differentiating the headspaces of healthy and mildew-infected plants even at early stages when disease symptoms are barely visible. These novel powdery mildew-related biomarkers are promising candidates for chemotyping and environmental monitoring in the field.

Virulence analysis of wheat powdery mildew races during 2019–2020 seasons in Egypt

Wheat powdery mildew (Blumeria graminis f. sp. tritici, Bgt) has become a principal disease occurring annually in Egypt followed by rusts which have been effectively controlled using resistance genes. Survey for fresh infected samples of powdery mildew was collected from fields of farmers and International Wheat Programs of five provinces, i.e., El-Gharbia, Kafr Sheikh, Dakahlia, Menoufia and Behera in Delta Egypt during 2019 and 2020 growing seasons. A total of 37 powdery mildew genes (Pm) including 16 known differentials were evaluated at the seedling stage for resistance and to identify the Bgt pathotypes prevailing in Delta Egypt. 84 isolates of powdery mildew, seven pathotypes were identified in the 2019 season, i.e., BIOE, FOOE, MOIE, MOOE, POEE, OOOE, POCE, while six pathotypes: MOOE, MMOE, COOE, CKKE, MOKE and HOOE were identified in the 2020 season. The pathotype MOOE showed the highest frequency of occurrence during the two seasons (62.16% and 62.18%), respectively. No virulence frequencies were detected in 27.02% of the tested Pm-genes, i.e., Pm11, Pm13, Pm16, Pm24, Pm25, Pm29, Pm32, Pm35, Pm36 and Pm37 during the two seasons of the study. Twenty-four of the 37 Pm-genes showed 5.56 up to 100% virulence frequencies during the two seasons of study, whereas three of the Pm-genes, i.e., Pm1b, Pm12 and Pm34 showed some fluctuations in virulence frequency with values of 16.67% in 2019 season, and 5.55%, 13.89% and 27.78% virulence frequencies in 2020, respectively.

The Spectrum of Weed Species and Fungal Pathogens in Stands of Alternative Fodder Crop Lolium Multiflorum Var. Westerwoldicum Growing up in a Drought-Prone Area in the Czech Republic

Annual ryegrass (Lolium multiflorum var. westerwoldicum) is cultivated in various areas of the world as a feed for live stock. Efforts to improve the production of high-quality feed in the face of deepening climate change have increased the demand for growing non-traditional types of crops, including ryegrass. The aims of the research were to determine the spectrum of weed and fungal pathogen species and to assess dangerous species of weeds and pathogens which negatively affect forage crops of annual ryegrass grown in dry conditions. In 2018-2019 the occurrence of weeds and fungal pathogens of ryegrass was evaluated in field conditions. The assessed lands were located in dry climatic conditions of South Moravia (Czech Republic). The vegetation recording was done on phytosociological plots of 12 m2. A total of 57 weed species were identified in the plots, where 12 species were toxic and 16 species were undesirable. The most problematic weeds and poisonous species were: Aethusa cynapium, Datura stramonium, Equisetum palustre, Euphorbia helioscopia, Fumaria officinalis and Solanum nigrum, which can cause health problems if present in cattle feed. A pathogenic infection caused by Blumeria graminis, Puccinia graminis var. graminicola and P. coronata var. coronata, Gaeumannomyces graminis and Drechslera sp. was identified on the ryegrass plants in the experimental plots during the vegetation. Blumeria graminis was the most abundant, but it did not endanger the final feed. The data was processed by CCA analysis.