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Pyrenophora tritici-repentis is the causative agent of tan spot in wheat. Among the necrotrophic effectors produced by the fungus, the most studied is the necrosis-inducing protein toxin Ptr ToxA, encoded by the ToxA gene. Previously, we identified ten strains of P. tritici-repentis from Kazakhstan and Russia, the amplified fragment of which with ToxA-specific primers turned out to be larger than expected. Sequencing of these fragments of three P. tritici-repentis strains revealed the presence of a 170 bp insertion element PtrHp2 located in exon 2 of the ToxA gene. The PtrHp2 sequence includes three pairs of mutually complementary regions of 16, 8, and 6 bp in length, forming a hairpin-type secondary structure. The inability of P. tritici-repentis strains possessing PtrHp2 in the ToxA gene to cause necrosis on the leaves of cv. Glenlea, which differentiates the presence of Ptr ToxA in the pathogen, has been established. This fact indicates a violation of the expression of the mutant ToxA gene. However, the mutant ToxA gene with PtrHp2 is retained in 45% of the fungal mitotic progeny. The fragments homologous to the PtrHp2 are found in noncoding parts of the ToxB gene and its homologs in P. tritici-repentis strains, as well as in the genomes of other fungi. This observation indicates the transposon nature of PtrHp2. [ABSTRACT FROM AUTHOR]

Tan spot disease of wheat (also known as yellow spot) is caused by the necrotrophic fungal pathogen Pyrenophora tritici‐repentis (Ptr). Initially described as a grass pathogen, Ptr has become a wheat pathogen of global importance. In Australia, tan spot was first recorded in 1952 as a minor wheat disease. However, by the 1970s tan spot had reached epidemic levels in Australia with yield losses of up to 49% reported in the north‐eastern region. A national survey carried out in 2007/2008 placed tan spot as the most economically important wheat disease with an estimated yield loss of 6%, corresponding to nearly a quarter of all disease losses. The incidence of tan spot in Australia has now markedly reduced with some wheat breeding programmes no longer considering tan spot disease resistance to be a priority trait. The disease can be effectively managed with integrated control strategies such as crop rotation, timely application of fungicides and removal of surface stubble. However, the key to the success of controlling tan spot disease in Australia has been achieved through wheat breeding programmes. The development of tan spot resistance resources suitable for the Australian climate was a concerted effort between national and international research organizations and Australian wheat breeders, supported by the Australian Grains Research Development Corporation (GRDC). While traditional breeding was essential to combat the disease, this article highlights the value of effector biology in assisting the development of resistant cultivars. [ABSTRACT FROM AUTHOR]

The research reported here was conducted to follow up on observations of durable adult‐plant resistance to net form net blotch in several Australian varieties of barley (Hordeum vulgare L.). Over 11 years, isolates of Pyrenophora teres f. teres were collected and used to inoculate barley varieties. The resistance of five varieties (Clipper, Schooner, Sloop SA, Buloke and Scope) endured until the ninth year. To investigate the genetic control of this durable resistance, doubled haploid lines developed from the F1 generation of a cross between Sloop SA and the susceptible variety Fathom were inoculated with an isolate that appeared fully virulent on Fathom and were evaluated for adult plant resistance. Six quantitative trait loci were mapped: three with resistance from Sloop SA and three with resistance from Fathom. Effects were additive across loci and transgressive segregation provided a few lines with better resistance than Sloop SA. Although the resistance investigated here is no longer effective, insights gained from this research could help guide ongoing efforts in resistance breeding and disease control. [ABSTRACT FROM AUTHOR]

Spot form net blotch, caused by Pyrenophora teres f. maculata, is a significant necrotrophic disease of barley that spread worldwide in the twentieth century. Genetic relationships were analyzed to determine the diversity, survival, and dispersal of a diverse collection of 346 isolates from Australia, Southern Africa, North America, Asia Minor, and Europe. The results, based on genome-wide DArTseq data, indicated that isolates from Turkey were lhe most differentiated with regional substructuring, together with individuals closely related to geographically distant genotypes. Elsewhere, population subdivision related to country of origin was evident, although low levels of admixturing was found that may represent rare genotypes or migration from unsampled populations. Canadian isolates were the next most diverged, and Australian and South African the most closely related. With the exception of Turkish isolates, multiple independent CypSIA mutation events (which confer insensitivity to demethylation inhibitor fungicides) between countries and within regions was evident, with strong selection for a transposable element insertion at the 3' end of lhe promoter and counterselection elsewhere. Individuals from Western Australia shared genomic regions and CypSIA haplotypes with South African isolates, suggesting a recent common origin. [ABSTRACT FROM AUTHOR]

This article reports the first occurrence of Pyrenophora avenicola causing leaf spot on oat plants in India. The disease was observed in Ludhiana, Punjab, and further surveillance revealed its presence in 52 out of 60 fields in the state. The symptoms included brownish-black lesions on the leaves, which gradually enlarged and formed blight. The fungus was isolated and identified through morphological and molecular techniques, confirming P. avenicola as the causal organism. Pathogenicity was also confirmed through inoculation experiments. This finding is significant as oat is an economically important crop, and neglecting this disease may lead to damage. [Extracted from the article]

Nitrogen (N) and silicon (Si) are mineral elements that have shown a reduction in the damage caused by tan spot (Pyrenophora tritici-repentis (Ptr)) in wheat. However, the effects of these elements were studied separately, and the N and Si interaction effect on wheat resistance to tan spot remains elusive. Histocytological and biochemical defense responses against Ptr in wheat leaves treated with Si (+Si) at low (LN) and high N (HN) inputs were investigated. Soil amendment with Si reduced the tan spot severity in 18% due to the increase in the leaf Si concentration (around 30%), but it was affected by the N level used. The superoxide dismutase (SOD) activity was higher in +Si plants and inoculated with Ptr, leading to early and higher H2O2 and callose accumulation in wheat leaf. Interestedly, phenylalanine ammonia-lyase (PAL) activity was induced by the Si supplying, being negatively affected by the HN rate. Meanwhile, catalase (CAT), and peroxidase (POX) activities showed differential response patterns according to the Si and N rates used. Tan spot severity was reduced by both elements, but their interaction does not evidence synergic effects in this disease's control. Wheat plants from −Si and HN and +Si and LN treatments recorded lower tan spot severity. [ABSTRACT FROM AUTHOR]

Pyrenophora teres f. teres (Ptt) is a severe pathogen to spring barley in Northern Europe. Ptt with relevant mutations in fungicide target proteins, sterol 14α-demethylase (CYP51A), cytochrome b (Cyt b), and succinate dehydrogenase (SDH) would put efficient disease control at risk. In the growing seasons of 2021 and 2022, 193 Ptt isolates from Estonia were analysed. In this study, mutation detection and in vitro fungicide sensitivity assays of single-spore isolates were carried out. Reduced sensitivity phenotype to mefentrifluconazole was evident in Ptt isolates with a F489L mutation in CYP51A or with 129 bp insert in the Cyp51A gene-promoter region. However, sensitivity to a prothioconazole-desthio remained high regardless of these molecular changes. The Ptt population was mostly sensitive to bixafen, fluxapyroxad, pyraclostrobin, and azoxystrobin. The sensitivity of fluxapyroxad and bixafen has been affected by two mutations, C-S135R and D-H134R, found in SDH subunits. The F129L mutation in Cyt b influenced azoxystrobin but not pyraclostrobin sensitivity. In total, 30 isolates from five fields had relevant mutations in three target protein genes simultaneously. Most of these isolates had a reduced sensitivity phenotype to mefentrifluconazole, fluxapyroxad, and azoxystrobin, while sensitivity to other tested fungicides remained high. Furthermore, possible sexual reproduction may enhance the pathogen's fitness and help it adapt to fungicides. [ABSTRACT FROM AUTHOR]

Resistance to fungicides is a global challenge as target proteins under selection can evolve rapidly, reducing fungicide efficacy. To manage resistance, detection technologies must be fast and flexible enough to cope with a rapidly increasing number of mutations. The most important agricultural fungicides are azoles that target the ergosterol biosynthetic enzyme sterol 14α-demethylase (CYP51). Mutations associated with azole resistance in the Cyp51 promoter and coding sequence can co-occur in the same allele at different positions and codons, increasing the complexity of resistance detection. Resistance mutations arise rapidly and cannot be detected using traditional amplification-based methods if they are not known. To capture the complexity of azole resistance in two net blotch pathogens of barley we used the Oxford Nanopore MinION to sequence the promoter and coding sequence of Cyp51A. This approach detected all currently known mutations from biologically complex samples increasing the simplicity of resistance detection as multiple alleles can be profiled in a single assay. With the mobility and decreasing cost of long read sequencing, we demonstrate this approach is broadly applicable for characterizing resistance within known agrochemical target sites. [ABSTRACT FROM AUTHOR]

Net blotch disease, caused by Pyrenophora teres f. teres (Ptt), is one of the most serious diseases of barley in Argentina. The in vitro sensitivity profile of Ptt to different fungicide mixtures currently used in Argentina was determined in isolates from different localities. Mycelial growth inhibition was measured, and the 50% inhibitory concentration (EC50) was estimated by simple logarithmic regression. In addition, the in vivo sensitivity of Ptt to the application of fluxapyroxad 5% + epoxiconazole 5% + pyraclostrobin 8.1% (FEP) was evaluated in greenhouse and field trials. The EC50 values ranged from 0.004 to 0.527 µg/mL, indicating that the fungicide mixtures tested were highly fungitoxic to all Ptt isolates tested. The in vivo and field fungicide efficacy averaged 99.9% and 79.5%, confirming a correlation between in vitro and in vivo sensitivity. The fungicide mixtures evaluated here were all highly fungitoxic and efficient for managing net blotch. [ABSTRACT FROM AUTHOR]

Pyrenophora teres f. teres (Ptt), the causal agent of net form net blotch (NFNB) disease, is an important and widespread pathogen of barley. This study aimed to quantify and characterize the virulence of Ptt isolates collected from experimental fields of barley in Hungary. Infection responses across 20 barley differentials were obtained from seedling assays of 34 Ptt isolates collected from three Hungarian breeding stations between 2008 and 2018. Twenty-eight Ptt pathotypes were identified. Correspondence analysis followed by hierarchical clustering on the principal components and host-by-pathogen GGE biplots suggested a continuous range of virulence and an absence of specific isolate × barley differential interactions. The isolates were classified into four isolate groups (IG) using agglomerative hierarchical clustering. One IG could be distinguished from other IGs based on avirulence/virulence on one to five barley differentials. Several barley differentials expressed strong resistance against multiple Ptt isolates and may be useful in the development of NFNB-resistant barley cultivars in Hungary. Our results emphasize that the previously developed international barley differential set needs to be improved and adapted to the Hungarian Ptt population. This is the first report on the pathogenic variations of Ptt in Hungary. [ABSTRACT FROM AUTHOR]

The plant material for research was collected in the period 2020 - 2022. Every year at the beginning of june, route surveys are conducted in different agroecological regions of the country. Variety, origin, date are noted for each sample. The main method for determining the species composition of the fungal pathogens involved in the leaf spotting complex is the comparativemorphological one. Symptoms are described on naturally infected durum wheat plants and compared with those on common wheat caused by the respective pathogens. Identification is made by direct observation of pathogen structures formed on plant tissue and when cultured in nutrient media and is based on a combination of morphological and cultural characters. The characters with the highest taxonomic value were taken into account: morphology and sizes of asexual and sexual mating, colony morphology. Microscopy of temporary preparations was performed. Often there are multiple spots on one leaf petura caused by one or more pathogens. Presence of Pyrenophora tritici-repentis was found in all investigated points. This species is represented by the largest number of isolates. In second place is Cladosporium herbarum, followed by Alternaria sp. [ABSTRACT FROM AUTHOR]

We investigated the ability of four plant and soil‐associated fungi to modify or degrade siderophore structures leading to reduced siderophore iron‐affinity in iron‐limited and iron‐replete cultures. Pyrenophora biseptata, a melanized fungus from wheat roots, was effective in inactivating siderophore iron‐chelating moieties. In the supernatant solution, the tris‐hydroxamate siderophore desferrioxamine B (DFOB) underwent a stepwise reduction of the three hydroxamate groups in DFOB to amides leading to a progressive loss in iron affinity. A mechanism is suggested based on the formation of transient ferrous iron followed by reduction of the siderophore hydroxamate groups during fungal high‐affinity reductive iron uptake. P. biseptata also produced its own tris‐hydroxamate siderophores (neocoprogen I and II, coprogen and dimerum acid) in iron‐limited media and we observed loss of hydroxamate chelating groups during incubation in a manner analogous to DFOB. A redox‐based reaction was also involved with the tris‐catecholate siderophore protochelin in which oxidation of the catechol groups to quinones was observed. The new siderophore inactivating activity of the wheat symbiont P. biseptata is potentially widespread among fungi with implications for the availability of iron to plants and the surrounding microbiome in siderophore‐rich environments. [ABSTRACT FROM AUTHOR]

Fungicide resistance in foliar fungal pathogens is an increasing challenge to crop production. Yield impacts due to loss of fungicide efficacy may be reduced through effective surveillance and appropriate management intervention. For stubble-borne pathogens, off-season crop residues may be used to monitor fungicide resistance to inform pre-planting decisions; however, appropriate sampling strategies and support sizes for crop residues have not previously been considered. Here, we used Pyrenophora teres f. teres (Ptt) with resistance to demethylase inhibitor fungicides as a model system to assess spatial dependency and to compare the effects of different sampling strategies and support sizes on pathogen density (Ptt DNA concentration) and the frequency of fungicide resistance mutation. The results showed that sampling strategies (hand-picked versus raked) did not affect estimates of pathogen density or fungicide resistance frequency; however, sample variances were lower from raked samples. The effects of differing sample support size, as the size of the collection area (1.2, 8.6, or 60 m2), on fungicide resistance frequency were not evident (P > 0.05). However, measures of pathogen density increased with area size (P < 0.05); the 60 m2 area yielded the highest Ptt DNA concentration and produced the lowest number of pathogenabsent samples. Sample variances for pathogen density and fungicide resistance frequency were generally homogeneous between area sizes. The pattern of pathogen density was spatially independent; however, spatial dependency was identified for fungicide resistance frequency, with a range of 110 m, in one of the two fields surveyed. Collectively, the results inform designs for monitoring of fungicide resistance in stubble-borne pathogens. [ABSTRACT FROM AUTHOR]

Net form net blotch (NFNB), caused by Pyrenophora teres f. teres, is an important barley disease. The centromeric region of barley chromosome 6H has often been associated with resistance or susceptibility to NFNB, including the broadly effective dominant resistance gene Rpt5 derived from barley line CIho 5791. We characterized a population of Moroccan P. teres f. teres isolates that had overcome Rpt5 resistance and identified quantitative trait loci (QTL) that were effective against these isolates. Eight Moroccan P. teres f. teres isolates were phenotyped on barley lines CIho 5791 and Tifang. Six isolates were virulent on CIho 5791, and two were avirulent. A CIho 5791 x Tifang recombinant inbred line (RIL) population was phenotyped with all eight isolates and confirmed the defeat of the 6H resistance locus formerly mapped as Rpt5 in barley line CI9819. A major QTL on chromosome 3H with the resistance allele derived from Tifang, as well as minor QTL, was identified and provided resistance against these isolates. F2 segregation ratios supported dominant inheritance for both the 3H and 6H resistance. Furthermore, inoculation of progeny isolates derived from a cross of P. teres f. teres isolates 0-1 (virulent on Tifang/avirulent on CIho 5791) and MorSM 40-3 (avirulent on Tifang/virulent on CIho 5791) onto the RIL and F2 populations determined that recombination between isolates can generate novel genotypes that overcome both resistance genes. Markers linked to the QTL identified in this study can be used to incorporate both resistance loci into elite barley cultivars for durable resistance. [ABSTRACT FROM AUTHOR]

Under this general name are included the symptoms caused by several phytopathogenic fungi. The negative effect on wheat plants is mainly due to the reduced photosynthesizing area and the accelerated aging of the leaves, which leads to the poor nutrition of the grain, significant losses in yield and lowering the quality of the production. This determines the great economic importance of these diseases and the need for their in-depth study. The term wheat septoria refers to diseases caused by three anamorphic fungal pathogens of the genus Septoria. The fungal pathogens involved in the leaf spotting complex include the tan spot diseases caused by Pyrenophora tritici-repentis, Cochliobolus sativus, Monographella nivalis and several species of the genus Alternaria. An important component of the integrated control of septoriosis is genetic resistance. No complete resistance has been established in wheat to Zimoseptoria tritici, Parastagonospora nodorum and Parastagonospora avenae f. sp. triticea. Over 20 major septoria tritici blotch resistance genes have been mapped. Sources of quantitative resistance that are longer lasting under field conditions have also been identified. [ABSTRACT FROM AUTHOR]

The aime of our research was to detect diseases and the effectiveness of some treatments on two-row barley during 2021-2023, in the Murighiol location, Tulcea County. The biological material was represented by the Romaniţa spring tworow barley variety. The experiment monitored the attack in treated and control variants. The analyzed pathogens were Blumeria graminis f. sp. hordei, the powdery mildew pathogen, Pyrenophora teres, the net blotch pathogen and Rynchosporium secalis, responsible for the appearance of rhynchosporiosis. The lowest values of the powdery mildew attack in the control variant were recorded in 2023, with values of the degree of attack of 14.9% and 23.5% in 2022. The application of treatments reduced the attack and had an effectiveness of over 73% in controlling powdery mildew during the analyzed period, around 71% in 2022 and 75% in 2023 in controlling net blotch. The rhynchosporiosis attack was sub-unitary. [ABSTRACT FROM AUTHOR]

Tan spot, a foliar disease of Triticum spp. such as bread wheat (T. aestivum L.) and durum wheat (T. turgidum ssp. durum (Desf.) Husn.) caused by the filamentous fungus Pyrenophora tritici-repentis (Died.) Drechsler leads to serious losses of crop yield and quality in some areas in Japan. P. tritici-repentis is classified into eight races according to the combinations of three necrotrophic effectors, PtrToxA, PtrToxB, and PtrToxC encoded by ToxA, ToxB, and ToxC1, respectively. Race classification has been based on reaction of a differential variety to necrotrophic effectors, which is tested by inoculation. Recent identification of the Tox genes and development of specific DNA markers have enabled us to classify races of P. tritici-repentis collected in Japan by Tox gene genotyping. We found that 17 strains collected from Triticum spp. in Japan were mainly race 1 or 2, because they carried ToxA as a toxin gene by current race classification; wheat genotype tsn1 is resistant to ToxA. Establishment of wheat cultivars carrying tsn1 would be most effective for decreasing agronomic losses caused by the disease in Japan. [ABSTRACT FROM AUTHOR]

Barley is one of the economically important crop species and the net form of net blotch (NFNB) caused by Pyrenophora teres f. teres has a significant impact on the quantity and quality of grain yield. Selection and inbreeding have resulted in a lack of genetic diversity in elite barley accessions. Old varieties often possess unique genetic traits that may have been lost in modern crop breeding. Therefore, the aim of the current study was to identify sources of resistance to barley NFNB in the collection of European old varieties. In this study, 431 European barley accessions were evaluated phenotypically under field conditions scoring APR to NFNB and genotypically using DArTseq. The range of adult plant resistance (APR) variability at the HA growth stage was sufficient to determine marker–trait associations (MTAs). The net form of net blotch at the HA stage was scored with a range of 1.0–4.0 according to a scale of 1–9, and GWAS identified 10 marker–trait associations (MTAs) for NFNB resistance. In the HA stage, two MTAs were identified on each chromosome 1H, 3H, 5H and 6H. Moreover, one was identified on the chromosome 7H and un. One of these MTA is localized on chromosome 6H, corresponding with findings from other studies, and could contribute to the exploration of genetic resistance of barley to NFNB. Additionally, the results of this study will be utilized to establish a Polish Gene Bank platform for precise breeding programs. [ABSTRACT FROM AUTHOR]

Tan spot, caused by the necrotrophic fungal pathogen Pyrenophora tritici-repentis (Ptr), is an important disease of durum and common wheat worldwide. Compared with common wheat, less is known about the genetics and molecular basis of tan spot resistance in durum wheat. We evaluated 510 durum lines from the Global Durum Wheat Panel (GDP) for sensitivity to the necrotrophic effectors (NEs) Ptr ToxA and Ptr ToxB and for reaction to Ptr isolates representing races 1 to 5. Overall, susceptible durum lines were most prevalent in South Asia, the Middle East, and North Africa. Genome-wide association analysis showed that the resistance locus Tsr7 was significantly associated with tan spot caused by races 2 and 3, but not races 1,4, or 5. The NE sensitivity genes Tscl and Tsc2 were associated with susceptibility to Ptr ToxC- and Ptr ToxB-producing isolates, respectively, but Tsnl was not associated with tan spot caused by Ptr ToxA-producing isolates, which further validates that the Tsnl--Ptr ToxA interaction does not play a significant role in tan spot development in durum. A unique locus on chromosome arm 2AS was associated with tan spot caused by race 4, a race once considered avirulent. A novel trait characterized by expanding chlorosis leading to increased disease severity caused by the Ptr ToxB-producing race 5 isolate DW5 was identified, and this trait was governed by a locus on chromosome 5B. We recommend that durum breeders select resistance alleles at the Tsr7, Tscl, Tsc2, and the chromosome 2AS loci to obtain broad resistance to tan spot. [ABSTRACT FROM AUTHOR]

This study was conducted to investigate the virulence variability among Moroccan isolates of Pyrenophora teres f. teres, commonly known as the net form net blotch, of barley. Infection responses of 109 single spore isolates of P. teres f. teres collected in 2016 were assessed for their interaction with 12 barley genotypes after inoculation at the seedling stage under controlled conditions. One week following inoculation, each plant's second and third leaves were rated for disease severity on a numerical reaction scale of 1–10. Plants rated < 5 and ≥ 5 were scored as resistant and susceptible to P. teres f. teres, respectively. Cluster analysis revealed three isolate clusters and five barley genotype clusters with highly variable mean infection levels. Only four isolates had the same low virulence profile, while each of the remaining 105 isolates exhibited a unique virulence spectrum displaying continuous infection reactions with no location effects. Furthermore, for the first time we document differential virulences in isolates recovered from the same leaf lesion. The barley genotypes displaying some level of resistance to the vast majority of isolates should be particularly useful as resistance sources in barley breeding programs in Morocco. However, given the necrotrophic lifestyle of this fungus and the regular cycles of sexual reproduction, complementary within-field diversification strategies for genetic resistances as well as non-host rotation should become important components of disease management strategies against this highly variable fungus. [ABSTRACT FROM AUTHOR]

BACKGROUND: Net blotch (NB), caused by Pyrenophora teres f. teres (Ptt), is an important disease of barley worldwide. NB control is commonly achieved through the use of fungicide mixtures including strobilurins, triazoles and carboxamides. Succinate dehydrogenase inhibitors (SDHI) are important components of fungicide management programs of barley diseases. However, during the last growing seasons in Argentina, barley fields sprayed with mixtures containing SDHI fungicides have shown failures in NB control. Here, we report the isolation and characterization of Argentine Ptt strains resistant to SDHI fungicides. RESULTS: Compared against a sensitive (wild‐type) reference strain collected in 2008, all 21 Ptt isolates collected in 2021 exhibited resistance to pydiflumetofen and fluxapyroxad both in vitro and in vivo. Concordantly, all of them presented target‐site mutations in any of the sdhB, sdhC and sdhD genes. Although the mutations detected have been previously reported in other parts of the world, this study documents for the first time the occurrence of double mutations in the same Ptt isolate. Specifically, the double mutation sdhC‐N75S + sdhD‐D145G confers high resistance to SDHI fungicides, while the double mutations sdhB‐H277Y + sdhC‐N75S and sdhB‐H277Y + sdhC‐H134R confer moderate levels of resistance in Ptt. CONCLUSIONS: SDHI‐resistance in Argentine Ptt populations is expected to increase. These findings emphasize the urgent need to perform a wider survey and a more frequent monitoring of SDHI sensitivity of Ptt populations and to develop and implement effective antiresistance tactics. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Necrotrophic fungi affect a wide range of plants and cause significant crop losses. For the activation of multi-layered innate immune defences, plants can be primed or pre-conditioned to rapidly and more efficiently counteract this pathogen. Untargeted and targeted metabolomics analyses were applied to elucidate the biochemical processes involved in the response of 3,5-dichloroanthranilic acid (3,5-DCAA) primed barley plants to Pyrenophora teres f. teres (Ptt). A susceptible barley cultivar ('Hessekwa') at the third leaf growth stage was treated with 3,5-DCAA 24 h prior to infection using a Ptt conidia suspension. The infection was monitored over 2, 4, and 6 days post-inoculation. For untargeted studies, ultra-high performance liquid chromatography coupled with high-resolution mass spectrometry (UHPLC–MS) was used to analyse methanolic plant extracts. Acquired data were processed to generate the data matrices utilised in chemometric modelling and multi-dimensional data mining. For targeted studies, selected metabolites from the amino acids, phenolic acids, and alkaloids classes were quantified using multiple reaction monitoring (MRM) mass spectrometry. 3,5-DCAA was effective as a priming agent in delaying the onset and intensity of symptoms but could not prevent the progression of the disease. Unsupervised learning methods revealed clear differences between the sample extracts from the control plants and the infected plants. Both orthogonal projection to latent structure-discriminant analysis (OPLS-DA) and 'shared and unique structures' (SUS) plots allowed for the extraction of potential markers of the primed and naïve plant responses to Ptt. These include classes of organic acids, fatty acids, amino acids, phenolic acids, and derivatives and flavonoids. Among these, 5-oxo-proline and citric acid were notable as priming response-related metabolites. Metabolites from the tricarboxylic acid pathway were only discriminant in the primed plant infected with Ptt. Furthermore, the quantification of targeted metabolites revealed that hydroxycinnamic acids were significantly more prominent in the primed infected plants, especially at 2 d.p.i. Our research advances efforts to better understand regulated and reprogrammed metabolic responses that constitute defence priming in barley against Ptt. [ABSTRACT FROM AUTHOR]

Pathogen attacks elicit dynamic and widespread molecular responses in plants. While our understanding of plant responses has advanced considerably, little is known of the molecular responses in the asymptomatic 'green' regions adjoining lesions. Here, we explore gene expression data and high-resolution elemental imaging to report the spatiotemporal changes in the asymptomatic green region of susceptible and moderately resistant wheat cultivars infected with a necrotrophic fungal pathogen, Pyrenophora tritici-repentis. We show, with improved spatiotemporal resolution, that calcium oscillations are modified in the susceptible cultivar, resulting in 'frozen' host defence signals at the mature disease stage, and silencing of the host's recognition and defence mechanisms that would otherwise protect it from further attacks. In contrast, calcium accumulation and a heightened defence response were observed in the moderately resistant cultivar in the later stage of disease development. Furthermore, in the susceptible interaction, the asymptomatic green region was unable to recover after disease disruption. Our targeted sampling technique also enabled detection of eight previously predicted proteinaceous effectors in addition to the known ToxA effector. Collectively, our results highlight the benefits of spatially resolved molecular analysis and nutrient mapping to provide high-resolution spatiotemporal snapshots of host–pathogen interactions, paving the way for disentangling complex disease interactions in plants. [ABSTRACT FROM AUTHOR]

Tan spot, caused by Pyrenophora tritici-repentis (Ptr), is a worrisome destructive foliar disease of wheat-growing areas around the world. Streptomyces spp. have been investigated as biocontrol agents because they beneficially interact with host plants and produce important bioactive substances that can act in the suppression of diseases in plants. In the present study, antifungal activity and plant growth-promoting of Streptomyces spp. strains 6(4), R18(6), and their consortium, were evaluated through in vitro and greenhouse assays. The Ultra High-Performance Liquid Chromatography-Quadrupole Time-of-Flight Mass Spectrometry (UHPLC-QTOF MS) technique was used to analyze the crude extract of each strain. The results of the in vitro tests showed that the 6(4) metabolites caused several abnormalities in the conidial germination of Ptr. This strain also produced indole acetic acid (IAA) and siderophores. Strain R18(6) did not alter conidial germination of Ptr, and produced IAA and phosphate solubilizers. In the greenhouse, the treatment 'seed inoculation plus foliar spray' with streptomycetes propagules and metabolites contributed to biomass gain, with no statistical difference between the strains (p < 0.05). Treatments with 6(4) 'seed inoculation', 'seed inoculation plus foliar spray', and consortium 'seed inoculation' showed the lowest percentage of injured area compared to other treatments (p < 0.05). UHPLC-QTOF MS data showed that erucamide is present in the culture of 6(4), but not in the culture of R18(6). Therefore, this substance is one of those involved in Ptr hyphal abnormalities, and R18(6) use indirect mechanisms of action to control Ptr. We concluded that these Streptomyces spp. and their metabolites have a promising potential for biological control of Ptr to protect wheat plants from tan spot damage. [ABSTRACT FROM AUTHOR]

The paper aimed to present alternative against the pathogen Pyrenophora teres (anamorph Drechslera teres) which parasitizes barley crop in western parts of Romania even beginning with late autumn period, observing the evolution and symptoms spreading of this fungus. Across the world, Pyrenophora teres causing the net blotch of barley is regarded as the major foliar disease in Hordeum vulgare L. Throughout its two form of Phyrenophora teres, however different from genetical point of view, P. teres f. sp. maculata and P. teres f. sp. teres causes economic losses by reducing yield and grain quality and poor emergence in area with a high biological pressure of the pathogen. The trial extends for two years (2019-2020, 2020-2021) in the same area of cropping (monoculture system) using same seed treatment list and following the seed-borne cereal fungi assessment protocol [(EPPO 1/19 (4)]. Trial setup consisted in complete randomized blocks, 6 treatments like fludioxinil, fluxapyroxad and mixture, every plot measuring 10 m2 and observations performed an al plants/1 m in length sample. When treated with two active ingredients the result obtained exerts an efficacy up to 98%, maintained in both trial years compared with the untreated plots where the pathogen was well established. [ABSTRACT FROM AUTHOR]

Drechslera tritici-repentis (Died.) Shoem. (teleomorph Pyrenophora tritici-repentis (Died.) Drechsler) is the causal agent of a tan spot, a major wheat disease worldwide. Wheat yield losses can reach up to 60%. Accurate and timely monitoring of harmful objects is crucial for effective crop protection against economically significant pathogens. Thus, in our study, we aim to evaluate the detection of tan spot operating spore trapping devices of various designs. As a result, the possibility of detecting tan spot pathogen spores using various spore-catching devices was shown. The number of pathogen spores caught by different devices varied from 1 pc. up to 18 pcs. depending on the design of the device, variety and sampling time. Our study demonstrates that spore traps of various designs help to detect tan spot prior to its visible manifestation at its minimum development (up to 1-5%). It's, crucial for the development of effective protective measures. [ABSTRACT FROM AUTHOR]

In recent years multi-parental mapping populations (MPPs) have been widely adopted in many crops to detect quantitative trait loci (QTLs) as this method can compensate for the limitations of QTL analyses using bi-parental mapping populations. Here we report the first multi-parental nested association mapping (MP-NAM) population study used to detect genomic regions associated with host-pathogenic interactions. MP-NAM QTL analyses were conducted on 399 Pyrenophora teres f. teres individuals using biallelic, cross-specific and parental QTL effect models. A bi-parental QTL mapping study was also conducted to compare the power of QTL detection between bi-parental and MP-NAM populations. Using MP-NAM with 399 individuals detected a maximum of eight QTLs with a single QTL effect model whilst only a maximum of five QTLs were detected with an individual bi-parental mapping population of 100 individuals. When reducing the number of isolates in the MP-NAM to 200 individuals the number of QTLs detected remained the same for the MP-NAM population. This study confirms that MPPs such as MP-NAM populations can be successfully used in detecting QTLs in haploid fungal pathogens and that the power of QTL detection with MPPs is greater than with bi-parental mapping populations. [ABSTRACT FROM AUTHOR]

A promising direction in the field of plant protection is the creation of remote sensing methods to detect the development of plant diseases based on the analysis of the reflected radiation spectra. Spectral analysis is a relatively simple non-invasive method that allows to obtain high quality data. The objects of the study were 6 varieties of winter wheat with different levels of resistance to tan spot (Pyrenophora tritici-repentis). The purpose of the present study was to assess, in the field conditions, the informativeness of the spectral optical parameters of winter wheat varieties and their mixtures with different susceptibility to the tan spot pathogen. Using the ASD FieldSpec 3 Hi-Res spectroradiometer, high-precision ground-based measurements of selected plant objects were carried out. Analysis of changes in the morphology of spectral signatures of the studied objects showed that the most promising spectral ranges for detecting the development of tan spot at the early stages are 1445–1775 nm and 2050–2450 nm. According to the results of univariate analysis of variance, the influence of wheat varieties and the degree of disease development was confirmed. The hypothesis that the less resistant the wheat variety to tan spot is, the faster is the decrease in the spectral brightness coefficient (SBC) values in the near infrared range of the spectrum and the increase in the red range of the spectrum was confirmed. [ABSTRACT FROM AUTHOR]

Spot form net blotch (SFNB) disease has been seriously limiting barley production in Tigray. As a result, there is a need to enhance barley production through the development of management options that can be effectively used in combating the SFNB problem. This research was conducted to evaluate the effect of Thiram and propiconazole on the severity of SFNB of barley. The experiment was conducted using a split-plot design with three replications. The cultivars included: HB-1307, HB-42, Fetina, and saesea were used. The fungicides were thiram and propiconazole as main plots and varieties are the sup plots respectively. The data were subjected to ANOVA using GenStat version 2018 software. HB-42 was found resistant while saesea was susceptible. The highest area under the disease progress curve (AUDPC) was recorded in untreated saesea (1517.7). The minimum AUDPC of SFNB (536.9) was in HB-42 with the spray of fungicides. The highest yield was in Fetina with sprayed (4.02 ton/ha) and the lowest was untreated HB-42 (2.288 ton /ha). Fetina with a spray of Thiram and Propiconazole in comparison with the unsprayed offered 2383.42% of the marginal rate of return so Fetina with the spray of Thiram and Propiconazole is recommended for profitable production. [ABSTRACT FROM AUTHOR]

Spot form net blotch, caused by Pyrenophora teres f. maculata, is a significant global disease of barley (Hordeum vulgare). Baudin, a barley cultivar that was until recently extensively grown in Western Australia, was reported as having minor seedling resistance. However, Baudin was highly susceptible to a local isolate, M3, suggesting that this isolate had gained virulence against a major susceptibility gene. M3 causes atypical lesions with pale centers early in the infection, with initial screens of a segregating population indicating that this was determined by a single locus in the Baudin genome. The susceptibility was semidominant in F1 progeny and the susceptibility gene, designated Spm1 (Susceptibility to P. teres f. maculata 1), mapped to a 190-kb section of the resistance gene-rich Mla region of chromosome 1H. Phenotyping with Ptm SP1, a non-M3 pathotype, identified a seedling resistance locus on 2H. Minor gene resistance is generally regarded as potentially durable, but our findings suggest the resistance to spot form net blotch in Baudin is nullified by strong susceptibility conferred by a separate locus on 1H. [ABSTRACT FROM AUTHOR]

The oat crop has been neglected due to its use in limitation as a forage crop rather than a staple food in most of the countries throughout the world. Also it is more prone to foliar diseases, especially Helminthosporium leaf blight (HLB, syn Pyrenophora leaf spot) disease in the Punjab, especially Ludhiana region. It emerged as a new disease that can infect over 70% of the field resulting in up to forage yield losses of 50 per cent throughout. Hence, this study was conducted to evaluate the 167 germplasm lines for disease severity and its infection based on 1–9 scale through artificial inoculation of fungal spores. These lines were classified under four different clusters based upon infection with majority falling under cluster 2 and cluster 3 with infection of more than 50%. Lines ranged from being highly susceptible (more than 75% infection) to moderately resistant (22% infection). These contrasting lines were used in disease progression studies and also in hybridization programme to develop populations for future mapping studies. The contrasting lines were analysed for polymorphism using 220 SSR markers, of which 47 markers were polymorphic. Also the mapping for HLB resistance genes/QTLs is being carried out under the current ongoing research project, which will be the first research to map the resistance genes/QTLs in the oats throughout India and the world. Identified lines also can be used in future breeding programme to develop resistant cultivars. [ABSTRACT FROM AUTHOR]

The global wheat disease tan spot is caused by the necrotrophic fungal pathogen Pyrenophora tritici‐repentis (Ptr) which secretes necrotrophic effectors to facilitate host plant colonization. We previously reported a role of the Zn2Cys6 binuclear cluster transcription factor Pf2 in the regulation of the Ptr effector ToxA. Here, we show that Pf2 is also a positive regulator of ToxB, via targeted deletion of PtrPf2 which resulted in reduced ToxB expression and defects in conidiation and pathogenicity. To further investigate the function of Ptr Pf2 in regulating protein secretion, the secretome profiles of two Δptrpf2 mutants of two Ptr races (races 1 and 5) were evaluated using a SWATH‐mass spectrometry (MS) quantitative approach. Analysis of the secretomes of the Δptrpf2 mutants from in vitro culture filtrate identified more than 500 secreted proteins, with 25% unique to each race. Of the identified proteins, less than 6% were significantly differentially regulated by Ptr Pf2. Among the downregulated proteins were ToxA and ToxB, specific to race 1 and race 5 respectively, demonstrating the role of Ptr Pf2 as a positive regulator of both effectors. Significant motif sequences identified in both ToxA and ToxB putative promoter regions were further explored via GFP reporter assays. [ABSTRACT FROM AUTHOR]

In wheat, major yield losses are caused by a variety of diseases including rusts, spike diseases, leaf spot and root diseases. The genetics of resistance against all these diseases have been studied in great detail and utilized for breeding resistant cultivars. The resistance against leaf spot diseases caused by each individual necrotroph/hemi-biotroph involves a complex system involving resistance (R) genes, sensitivity (S) genes, small secreted protein (SSP) genes and quantitative resistance loci (QRLs). This review deals with resistance for the following four-leaf spot diseases: (i) Septoria nodorum blotch (SNB) caused by Parastagonospora nodorum; (ii) Tan spot (TS) caused by Pyrenophora tritici-repentis; (iii) Spot blotch (SB) caused by Bipolaris sorokiniana and (iv) Septoria tritici blotch (STB) caused by Zymoseptoria tritici. [ABSTRACT FROM AUTHOR]

Barley leaf stripe, caused by Pyrenophora graminea, is an essential systemic seed-borne disease in barley worldwide. Barley is a major cereal crop in the Qinghai–Tibet Plateau, and barley production has been threatened by leaf stripe in this region, particularly in organic farming regions. Detecting the pathogen in infected barley seeds is crucial for managing barley leaf stripe. In this study, a loop-mediated isothermal amplification (LAMP) assay was developed to detect the pathogen based on primers designed based on the sequence of the pig 14 gene (GenBank: AJ277800) of P. graminea. The optimal concentrations of MgSO4, dNTPs, and enzymes in the LAMP reaction system were established as 10.0 mM, 1.0 mM, and 8 U in a 25 μL reaction volume, respectively. The established LAMP methods for detecting P. graminea were optimally performed at 63 °C for 70 min with high reliability. The minimum detection limit was 1 × 10−2 ng·μL−1 in the 25 μL reaction system. The specificity of LAMP for P. graminea was validated with eight fungal species. All DNA extracts from P. graminea-infected barley seeds with incubation, intact, and smashed treatments were applied in LAMP and confirmed to enable the detection of the pathogen. The LAMP assay in this study could facilitate the detection of P. graminea in barley seeds onsite, provide information for seed health certificates, and help decide on seed treatment in leaf stripe management. [ABSTRACT FROM AUTHOR]

Wheat is the main crop in the world. Tan spot caused by Pyrenophora tritici-repentis (Ptr) is a destructive disease in wheat-producing areas. Accumulation of phenolic acids at the onset of the fungal infection induces plant's resistance to tan spot. This study evaluated the effect of phenolic compound accumulation on the resistance to tan spot in wheat-pathogen interactions. Five different wheat cultivars including Glenlea, Salamouni, Moghan 3, Morvarid, and Bolani were studied at three different time points after inoculation with Ptr. The composition and concentration of phenolic acid including ferulic acid, p-coumaric acids, vanillic acid, chlorogenic acid, and rutin were detected using high-performance liquid chromatography and analyzed according to standard curves. Results showed considerable accumulation of ferulic acid, p-coumaric acids, vanillic acid, chlorogenic acid, and rutin in treatment with Ptr during 7 days postinoculation in resistant and partially resistant cultivars compared with the susceptible ones. Ferulic acid was the most abundant phenolic compound in Salamouni (16.77±0.16 mg g-1 dw), Moghan 3 (17.76±0.00 mg g-1 dw), and Morvarid (23.11±0.00 mg g-1 dw) at 7 dpi. The obtained data indicated that the identified phenolic acids had enhanced and improved the wheat resistance to the fungal pathogen. Linear Pearson's coefficient analysis showed a positive correlation between some phenolic acids concentration and also between them and flavonoid rutin in wheat cultivars during infection. These findings highlighted the capacity of phenolic compounds as potential tools for the identification of resistance in wheat-pathogen interactions. [ABSTRACT FROM AUTHOR]

The research followed the evolution of the mycosis attack of autumn barley cultivated in the classical culture and during the conversion period to switch to the ecological culture, in the agricultural year 2021-2022, in Tulcea county. The frequent micromycetes were Pyrenophora teres, Pyrenophora graminea, Puccinia hordei, Rhynchosporium secalis and Blumeria graminis f.sp. hordei. In the barley cultivated in the two systems, the incidence of attack by Pyrenophora teres and Puccinia hordei was 100%. The frequency of the Pyrenophora graminea attack was 5% and 6% in the control variants. The powdery mildew attack was more sensitive to barley in the conventional culture and the Rhynchosporium secalis attack was subunit in both culture systems. The application of the treatment in the conventional system ensured an effectiveness of over 64%. [ABSTRACT FROM AUTHOR]

Cereal production in Australia is severely impacted by stubble-borne pathogens which can survive multiple seasons within cereal residues (stubble). Microwave radiation may be able to reduce or eliminate the pathogens, but the energy requirements first need defining. Hence, the dielectric properties of wheat and barley stubble with different pathogen loads were investigated at 10%, 15%, 30% and 100% moisture content using an open-ended coaxial probe in a spectral band covering 915, 2450, and 5800 MHz. A significant increase in dielectric constant and loss factor was observed with increasing stubble moisture. The dielectric constant and loss factor were lower in the crown (basal) section of stubble compared with the stem (20 cm from base), due to differences in density. When stubble moisture was 100%, the loss factor of barley was higher than wheat. Infection of stubble by different pathogens did not affect the dielectric properties. Microwave heating could therefore be an effective method to heat cereal stubble to eradicate a range of cereal pathogens, especially at lower frequencies and high moisture content, at which the loss factor is high. This research serves as a starting point to define requirements for further development of effective microwave radiation treatments under field conditions. [ABSTRACT FROM AUTHOR]

The current research aimed to identify and genotype barley lines and varieties resistant to the fungal disease net blotch Pyrenophora teres Drechsler [anamorph Drechslera teres (Sacc.) Shoem]. Widely distributed Bulgarian and foreign elite barley genotypes were the object of the study. So far, all the varieties constituting the varietal structure of Bulgaria were valued as medium-sensitive (MS 4, 5) to very sensitive (VS 8, 9) according to their phenotypic reaction to net blotch. The genotypes used as resistance identifiers from the global gene banks, as a reference, showed sensitivity to local isolates. All barley forms of different origins, forming the trait collection were subjected to selection and genetic analysis. An ISSR marker system was used to genotype certain barley forms to their different phenotype reactions to Pyrenophora teres. We report quantitative trait loci (QTL) for potential net blotch resistance using combined data from ISSR analysis and phenotype observations. The obtained genetic map gives an idea of the identified polymorphisms' relation, which may further serve to establish their additional links with the behavior of the varieties with the examined plant pathogen. Moreover, the created map can also be used to identify associations of these markers with resistance to other pest levels, thereby allowing the identification of genomic regions contributing to horizontal (multiple) resistance, such as those of particular interest. Identification of ISSR markers associated with major QTLs which can be used for marker-assisted selection (MAS), and their validation in unrelated barley populations. [ABSTRACT FROM AUTHOR]

Pyrenophora tritici-repentis (Ptr), family Pleosporaceae, is a common wheat pathogen in all wheat-growing regions around the globe. It is widely studied in North America, South America, and North Africa, while data about the fungus genetic diversity in Europe is still insufficient. This study aimed to describe the variation of morphological traits and toxin production of strains collected in Latvia and Belarus. Twenty-one isolates from Latvia, and 12 from Belarus were sampled in 2019 for morphological evaluation in culture and necrotrophic effector gene determination by PCR. All isolates were grouped into nine different morphotypes. Five of these morphotypes were unique for isolates from Latvia, one for Belarus, and three morphotypes were occurring in both countries. No association between the host and the pathogen morphotype was observed. ToxA gene was detected in 44% of the analysed isolates. For 52% of the isolates, PCR did not confirm the presence of any known effector genes of Pyrenophora tritici-repentis. ToxB and toxb were found only in one isolate from Latvia. The studies need to be continued to evaluate the diversity of the pathogen depending on the host species. [ABSTRACT FROM AUTHOR]

QUAST (version: 5.0.2) was used to assess the quality of the genome assembly and to determine the general statistics of the genomes (including genome size, GC content, N50, L50, number of contigs, largest contig size, and the average number of mismatches per 100 kbp) (Mikheenko et al. [98]). IMA genome-F17: Draft genome sequences of an Armillaria species from Zimbabwe, Ceratocystis colombiana, Elsinoë necatrix, Rosellinia necatrix, two genomes of Sclerotinia minor, short-read genome assemblies and annotations of four Pyrenophora teres isolates from barley grass, and a long-read genome assembly of Cercospora zeina To confirm the identity of the two I S. minor i draft genomes presented in this announcement, the partial small subunit ribosomal RNA gene, complete internal transcribed spacer 1 and 5.8S ribosomal RNA gene, and partial internal transcribed spacer 2 (ITS region) were extracted from the two assembled genomes (CBS 339.39 and SsChi) as well as from the LC41 reference genome (Yang et al. [164]). Draft genome sequence of an Armillaria species from Zimbabwe Introduction The genus Armillaria includes at least 38 species, most of which are facultative necrotrophs (Gregory and Rishbeth [49]). A total of 11,570 gene models were predicted from this new genome assembly, which is 1377 more than the 10,193 gene models predicted from a previously published Illumina-based genome assembly and annotation (Wingfield et al. [160]). [Extracted from the article]

Background: In fungal plant pathogens, genome rearrangements followed by selection pressure for adaptive traits have facilitated the co-evolutionary arms race between hosts and their pathogens. Pyrenophora tritici-repentis (Ptr) has emerged recently as a foliar pathogen of wheat worldwide and its populations consist of isolates that vary in their ability to produce combinations of different necrotrophic effectors. These effectors play vital roles in disease development. Here, we sequenced the genomes of a global collection (40 isolates) of Ptr to gain insights into its gene content and genome rearrangements. Results: A comparative genome analysis revealed an open pangenome, with an abundance of accessory genes (~ 57%) reflecting Ptr's adaptability. A clear distinction between pathogenic and non-pathogenic genomes was observed in size, gene content, and phylogenetic relatedness. Chromosomal rearrangements and structural organization, specifically around effector coding genes, were detailed using long-read assemblies (PacBio RS II) generated in this work in addition to previously assembled genomes. We also discovered the involvement of large mobile elements associated with Ptr's effectors: ToxA, the gene encoding for the necrosis effector, was found as a single copy within a 143-kb 'Starship' transposon (dubbed 'Horizon') with a clearly defined target site and target site duplications. 'Horizon' was located on different chromosomes in different isolates, indicating mobility, and the previously described ToxhAT transposon (responsible for horizontal transfer of ToxA) was nested within this newly identified Starship. Additionally, ToxB, the gene encoding the chlorosis effector, was clustered as three copies on a 294-kb element, which is likely a different putative 'Starship' (dubbed 'Icarus') in a ToxB-producing isolate. ToxB and its putative transposon were missing from the ToxB non-coding reference isolate, but the homolog toxb and 'Icarus' were both present in a different non-coding isolate. This suggests that ToxB may have been mobile at some point during the evolution of the Ptr genome which is contradictory to the current assumption of ToxB vertical inheritance. Finally, the genome architecture of Ptr was defined as 'one-compartment' based on calculated gene distances and evolutionary rates. Conclusions: These findings together reflect on the highly plastic nature of the Ptr genome which has likely helped to drive its worldwide adaptation and has illuminated the involvement of giant transposons in facilitating the evolution of virulence in Ptr. [ABSTRACT FROM AUTHOR]

Diseases caused by crop residue-dependent pathogens have increased during the last decades in Uruguayan agriculture systems, in particular Pyrenophora tritici-repentis and Cochliobolus sativus. Consequently, we searched for the presence of fungal antagonists for these pathogens, particularly Trichoderma. Seven species of Trichoderma inhabiting soils and crop residues were identified. Strains of all identified species had high in vitro antagonistic activity against both pathogens. These results confirm the presence of Trichoderma spp. naturally inhabiting crop residues and soils, with potential to inhibit C. sativus and P. tritici-repentis. Managing antagonist populations is a promising and underdeveloped strategy that warrant further investigation. [ABSTRACT FROM AUTHOR]

In European QoI monitoring studies from 2019 on Pyrenophora teres, the causal agent of net blotch in barley, an isolate (ISO-2210) was identified with a level of QoI resistance that had never been observed before. ISO-2210 is highly resistant to QoI fungicides, which is caused by the G143A mutation in the mitochondrial-inherited cyt b gene. A part of its cyt b gene around codon 143 differs from P. teres and is identical to P. tritici-repentis, the causal agent of tan spot in wheat. The rest of the cyt b gene and other analyzed genes from mitochondrial and chromosomal DNA are identical to P. teres. In genes which differed between net type and spot type, the ISO-2210 sequences were identical to those of net type. ISO-2210 morphologically resembles P. teres and is pathogenic on barley, where it produces typical net blotch symptoms. An analysis of European isolates from 2019 and field samples from 2019 and 2020 did not indicate additional findings of such "hybrid"-isolates. [ABSTRACT FROM AUTHOR]

Tan spot disease, which is caused by Pyrenophora tritici-repentis (Ptr), is one of the most significant wheat diseases in Kazakhstan, an important wheat-growing region in Central Asia. In this study, we aimed to investigate the race composition of Ptr responsible for tan spot in Kazakhstan through the phenotypic and genotypic characterization. During 2019–2020, samples of Ptr isolates were collected for analysis in six regions of the Republic of Kazakhstan from commercial and experimental fields of bread and durum wheat affected by tan spot disease. Race classification was based on inoculation bioassay of 167 isolates to four corresponding differential wheat genotypes, with a PCR assay used to identify the effector genes. The characterization of these isolates showed they belonged to four different known races (Races 1–4) in addition to one potential atypical race that does not fit into the current race system. We identified two races, Races 1 and 2, as critical for wheat production in Kazakhstan, as they occur throughout the study area. Most isolates exhibited amplification of the ToxA gene, a necrosis-causing effector, which is consistent with the inoculation results; only Races 3 and 4 did not show amplification of the ToxA gene. Inoculating wheat with the sixteen isolates of Ptr resulted in disease, the classification of which was similar to that caused by Race 8, according to the current wheat differential set. However, according to the genetic characterization, these isolates did not possess the associated effector gene expected for Race 8 assignment; therefore, we designated them as isolates of an atypical race. According to our results, race classification should be based on both phenotypic and genotypic analyses, where possible, to adequately capture the breadth of physiological variation among Ptr isolates, in addition to the possible expansion of the differential set. [ABSTRACT FROM AUTHOR]

Twenty-four fungal endophytes, isolated from a wild relative of barley, Elymus repens, were screened in barley against an isolate of Fusarium culmorum and an isolate of Pyrenophora teres under controlled conditions. In all experiments, the endophytes were applied individually as seed dressings. Five endophytes could significantly reduce symptoms of Fusarium culmorum (Periconia macrospinosa E1 and E2, Epicoccum nigrum E4, Leptodontidium sp. E7 and Slopeiomyces cylindrosporus E18). In particular, treatment with Periconia macrospinosa E1 significantly reduced Fusarium symptoms on roots by 29–63% in two out of four experiments. Using, a gfp transformed isolate of P. macrospinosa E1, it was possible to show that the fungus was present on roots 14 days after sowing, coinciding with the disease scoring. To test for a potential systemic effect of the seed treatment, eight endophyte isolates were tested against the leaf pathogen Pyrenophora teres. Three isolates could significantly reduce symptoms of P. teres (Lasiosphaeriaceae sp. E10, Lindgomycetaceae sp. E13 and Leptodontidium sp. E16). Seed treatment with Lasiosphaeriaceae sp. E10 reduced net blotch leaf lesion coverage by 89%, in one out of three experiments. In conclusion, specific endophyte isolates exerted varying degrees of protection in the different experiments. Nevertheless, data suggest that endophytic strains from E. repens in a few cases are antagonistic against F. culmorum and P. teres, but otherwise remain neutral when introduced to a barley host in a controlled environment. [ABSTRACT FROM AUTHOR]

The bioactive compounds produced by Streptomyces spp. bacteria can inhibit and reduce the incidence of phytopathogenic fungi in agricultural crops. In this study, two Streptomyces strains 6(4) and R18(6) were tested separately and in a consortium and demonstrated antifungal activity against the phytopathogenic fungus Pyrenophora tritici-repentis (Ptr) that causes tan spots in wheat plants. Streptomyces isolates inhibited mycelial growth and they induce changes in hyphal development in the germination of Ptr. In the dual culture assay, the Streptomyces 6(4) strain inhibited growth of Ptr by 44% and in the agar well diffusion assay, produced the largest inhibition halos when the crude extract was tested (≥20 mm). The detached leaf assay showed that Streptomyces 6(4) and R18(6) strains and consortium crude extracts, reduced the disease index on the leaves of wheat, with 100, 90, and 95% biocontrol efficacy, respectively. Inoculating seeds with the propagules of spores of the same strains, 6(4), R18(6) and consortium, also resulted in biocontrol of the pathogen on detached leaves, although with 48, 53.08 and 60% biocontrol efficacy respectively. Therefore, we can conclude that the crude extracts of these isolates have the potential to control the fungus Pyrenophora tritici-repentis and reduce the symptoms of tan spot in wheat. [ABSTRACT FROM AUTHOR]

The genus Pyrenophora includes two important cereal crop foliar pathogens and a large number of less well-known species, many of which are also grass pathogens. Only a few of these have been examined in terms of secondary metabolite production, yet even these few species have yielded a remarkable array of bioactive metabolites that include compounds produced through each of the major biosynthetic pathways. There is little overlap among species in the compounds identified. Pyrenophora tritici-repentis produces protein toxin effectors that mediate host-specific responses as well as spirocyclic lactams and at least one anthraquinone. Pyrenophora teres produces marasmine amino acid and isoquinoline derivatives involved in pathogenesis on barley as well as nonenolides with antifungal activity, while P. semeniperda produces cytochalasans and sesquiterpenoids implicated in pathogenesis on seeds as well as spirocyclic lactams with phytotoxic and antibacterial activity. Less well-known species have produced some unusual macrocyclic compounds in addition to a diverse array of anthraquinones. For the three best-studied species, in silico genome mining has predicted the existence of biosynthetic pathways for a much larger array of potentially toxic secondary metabolites than has yet been produced in culture. Most compounds identified to date have potentially useful biological activity. [ABSTRACT FROM AUTHOR]

Leaf stripe disease caused by Pyrenophora graminea is an economically significant disease of cultivated barley worldwide, including Iran. Considering economic impact of this disease on barley industry in Iran, in this study genetic diversity of P. graminea populations mainly collected from barley (229 isolates) in different regions of East Azerbaijan Province was examined using ISSR and RAPD molecular markers. The average polymorphic information content (PIC) values for ISSR and RAPD were 0.28 in both markers, and a significant correlation was observed between ISSR and RAPD data (r =.78, p <.05). No clear clustering was found within P. graminea populations in relation to their geographical origins. Applying the unweighted pair group method with arithmetic mean (UPGMA) procedure and principal coordinates analysis (PCoA) revealed no obvious clustering of isolates based on geographic region. Totally, gene diversity of 0.2 was noticed among P. graminea isolates. High level of genetic differentiation (PhiPT = 0.257; p ≤.001), with 74% of the genetic variation occurring within populations and 26% occurring among populations, indicated the existence of population differentiation. In addition, a moderate amount of gene flow (Nm = 1.1985) was found between populations. Information obtained from this study may be beneficial to design and improve management strategies such as breeding resistant barley varieties to leaf stripe disease. [ABSTRACT FROM AUTHOR]

Tan spot, caused by Pyrenophora tritici-repentis, is an economically important foliar disease of wheat in Kazakhstan. Population structure of the pathogen changes every year due to climate change. This study aimed to characterize the race structure of P. tritici-repentis isolates recovered from wheat in south and north Kazakhstan, and identify tan spot resistance in host genotypes based on disease phenotypes and molecular screening. Virulence profiles were determined within 40 isolates of the pathogen from wheat crops during the 2020 growing season. Seven races, (1, 3, 4, 5, 6, 7 and 8) were identified. A collection of 80 wheat accessions, including promising lines and cultivars from Kazakhstan and Russia, were evaluated for their reactions to races 1 and 5 of the pathogen, and to Ptr ToxA and Ptr ToxB, using greenhouse assessments and molecular markers diagnostic for the Tsn1 and Tsc2 genes. From a practical viewpoint, 18 wheat genotypes were insensitive to the two races and the two Ptr toxins. This resistant germplasm can be used in breeding programmes aiming to develop wheat varieties resistant to P. tritici-repentis. [ABSTRACT FROM AUTHOR]