Search Results (29)

Tan spot of wheat, caused by the fungus Pyrenophora tritici-repentis (Ptr), is one of the most destructive foliar diseases of wheat worldwide and in Kazakhstan. Expansion of wheat plantings, the adoption of no-till methods, and the use of ineffective fungicides contribute to the accumulation of inoculum and the spread of the pathogen. Despite the important role of fungicides in plant protection, data on the susceptibility of Ptr populations in Kazakhstan are lacking. This study, for the first time, assessed the susceptibility of Ptr isolates from various regions of Kazakhstan to QoI and DMI fungicides. A predominance of genotypes associated with ToxA (82.9%) was found, with a limited distribution of ToxB (7.9%). Propiconazole demonstrated the highest efficacy, inhibiting mycelial growth by an average of 70.85%, followed by pyraclostrobin (69.04%), while azoxystrobin demonstrated lower efficacy (41.47%). Molecular analysis revealed the widespread prevalence of the G143A mutation in the cytochrome b gene, associated with resistance to the QoI fungicide. These results indicate the emergence of strobilurin resistance in Ptr populations in Kazakhstan and highlight the need for regular monitoring of fungicide susceptibility and the development of effective resistance management strategies. Full article

The foliar pathogens of wheat, particularly Zymoseptoria tritici and Pyrenophora tritici-repentis, represent a significant threat to yield. We used a SEIR (Susceptible–Exposed–Infected–Removed) model to quantify epidemic dynamics based on different fungicide application strategies, focusing on the daily dynamic growth rate r(t) (net infection increase) and the removal rate γ(t) (loss infectious tissue) after BBCH 37. In Scenario A (treatment of seed with Systiva^®), the r(t) of Z. tritici was positive only during the early phase of the epidemic, followed by progressive suppression over time, while the r(t) for P. tritici-repentis remained negative throughout. Scenario B (seed treatment combined with foliar propiconazole) resulted in uniformly negative r(t) values for both pathogens, indicating stronger and sustained suppression. These findings highlight the practical utility of epidemic growth rate modeling for evaluating fungicide strategies and support integrated seed + foliar applications as a robust approach to disease management in wheat. Full article

Pyrenophora tritici-repentis (Ptr), the causal agent of tan spot, is a necrotrophic fungus that represents a significant threat to wheat production worldwide. The development of resistant cultivars is limited by an incomplete understanding of wheat defence responses against Ptr. Here, weighted gene co-expression network analysis (WGCNA) was applied to RNA-seq data from resistant (Robigus) and susceptible (Hereward) wheat lines before and after Ptr infection to identify coordinated host responses. Eight co-expression modules were identified, three of which were linked to either resistance, susceptibility, or Ptr infection. The resistance-associated module was enriched with chloroplast ribosomal machinery genes (e.g., 50S ribosome-binding GTPase, L28, L6), and transcriptional regulators. This suggested that maintaining chloroplast function, coupled with large-scale transcriptional reprogramming, was important for resistance. The susceptibility-associated module indicated the high expression of post-transcriptional modifiers, including SGS3, RBX1, and SENPs. The Ptr-responsive module showed common responses in both genotypes and included several defence-related genes (nucleotide-binding domain leucine-rich repeat R-genes [NLRs], chitinases, beta-1,3-glucanases) and metabolic pathways, such as phenylpropanoid biosynthesis and nitrogen metabolism (phenylpropanoid ammonia lyase [PAL], cytochrome P450s, glutamine synthase, and ammonium transporters). These results define distinct and shared molecular networks that are linked to resistance and susceptibility, providing valuable candidate genes for functional validation that could ultimately be exploited to enhance wheat resilience against necrotrophic fungal pathogens. Full article

Phytopathogenic fungi represent a significant biotic stress affecting global agriculture, often causing severe diseases and, in some cases, leading to plant death. They have been isolated from economically important crops, including cereals, legumes, and fruits. Among the compounds produced by fungi, phytotoxins play a key role in disease development by interfering with host physiological processes. In this study, organic extracts from Cercospora kikuchii, Cercospora nicotianae, Cercospora sojina, Diaporthe longicolla, Septoria glycines, Pyrenophora teres, and Pyrenophora tritici-repentis, isolated from three major Argentine crops, were first screened for the in vitro production of phytotoxic metabolites. Subsequently, selected metabolites were dereplicated using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and nuclear magnetic resonance (NMR) spectroscopy. The phytotoxins identified varied according to the fungal species and extraction conditions. Cercosporin, putaminoxin, scytalone, and isosclerone were identified. These findings underscore the need for further chemical investigation to comprehensively characterize the metabolome of these phytopathogens and clarify their roles in plant–pathogen interactions. Full article

Tan spot disease, caused by Pyrenophora tritici-repentis, poses a significant threat to wheat production worldwide. Early detection and precise fungicide application are essential for effective disease management. This study explores the potential of Raman spectroscopy—specifically surface-enhanced Raman spectroscopy (SERS) and coherent anti-Stokes Raman scattering (CARS)—as non-invasive tools for identifying fungal infection and assessing wheat’s biochemical response to propiconazole treatment. The methodology is entirely theoretical; no laboratory experiments were conducted. Instead, all spectral graphs and figures were generated through a collaborative process between the author and Microsoft Copilot, which served as a rendering tool. These AI-assisted visualizations simulate Raman responses based on known molecular interactions and literature data. The results demonstrate the conceptual feasibility of Raman-based diagnostics for precision agriculture, offering a sustainable approach to disease monitoring and fungicide management. Full article

The virulence gene ToxA has been proposed to be horizontally transferred between three fungal wheat pathogens (Parastagonospora nodorum, Pyrenophora tritici-repentis, and Bipolaris sorokiniana) as part of a conserved ~14 kb ToxhAT transposon. Here, our analysis of 2137 fungal species-representative assemblies revealed that the ToxA gene is an isolate of Alternaria ventricosa and shows a remarkable 99.5% similarity to those found in B. sorokiniana and P. tritici-repentis. Analysis of the regions flanking ToxA within A. ventricosa revealed that it was embedded within a 14 kb genomic element nearly identical to the corresponding ToxhAT regions in B. sorokiniana, P. nodorum, and P. tritici-repentis. Comparative analysis further showed that ToxhAT in A. ventricosa resides within a larger mobile genetic element, which we identified as a member of the Starship transposon superfamily, named Frontier. Our analysis demonstrated that ToxhAT has been independently captured by three distinct Starships—Frontier, Sanctuary, and Horizon—which, despite having minimal sequence similarity outside of ToxhAT, facilitate its mobilization. These findings place Frontier, Sanctuary, and Horizon within a growing class of Starships implicated in the horizontal transfer of adaptive genes among fungal species. Moreover, we identified three distinct HGT events involving ToxA across these four fungal species, reinforcing the hypothesis of a single evolutionary origin for the ToxhAT transposon. These findings underscore the pivotal role of transposon-mediated HGT in the adaptive evolution of eukaryotic pathogens, offering new insights into how transposons facilitate genetic exchange and shape host–pathogen interactions in fungi. Full article

Tan spot (Pyrenophora tritici-repentis) and stripe rust (Puccinia striiformis f. sp. tritici) are major foliar diseases of wheat, causing significant yield losses globally. This study evaluated the efficacy of fungicide seed treatments in managing these diseases during early growth stages under greenhouse, growth chamber, and field conditions in the Northern Great Plains. Winter and spring wheat cultivars were treated with pyraclostrobin or combinations of thiamethoxam, difenoconazole, mefenoxam, fludioxonil, and sedaxane, among others. Greenhouse and growth chamber plants were inoculated with the respective pathogens, while field trials relied on natural inoculum. Fungicide treatments significantly reduced stripe rust severity (up to 36%) (p ≤ 0.05) and moderately reduced tan spot severity during early growth stages (15–20%). Treated plants demonstrated a 30–40% improvement in plant vigor, and a 25–50% increase in winter survival. Additionally, grain yield in treated plots increased by 25–50% (p ≤ 0.05), with test weight and protein content improving by 10% and 15%, respectively. These findings demonstrate the potential of fungicide seed treatments as an integrated pest (or pathogen) management (IPM) strategy to enhance early foliar disease control and wheat productivity. Full article

Tan spot caused by Pyrenophora tritici-repentis is a severe threat to wheat production in all major wheat-growing regions. Sustainable tan spot control can be achieved by an integrated approach, including responsible management of fungicide sprays. The data about the sensitivity of P. tritici-repentis to various fungicides in the Baltic Sea region are rare. In this study, we described the variation of P. tritici-repentis sensitivity to four fungicide active ingredients to detect the formation of resistance to the most commonly used quinone-outside inhibitor (QoI) and 14α-demethylase inhibitor (DMI) fungicides in the pathogen’s population in Latvia. The effect of prothioconazole, mefentrifluconazole, pyraclostrobin, and azoxystrobin on 93 P. tritici-repentis strains from various hosts was tested in vitro by assessing mycelium linear growth inhibition at three different active ingredient concentrations (0 0.01, 0.1 and 0.5 mg L⁻¹). Pathogen sensitivity significantly (p < 0.001) varied between the fungicide active ingredients and strains. The prothioconazole (concentration 0.5 mg L⁻¹) had the most significant effect, with a median mycelial growth inhibition of 70.34%, followed by pyraclostrobin (47.02%), azoxystrobin (24.24%), and mefentrifluconazole (11.11%). Mutation G143A was detected in cytb gene sequences and confirmed the resistance formation in Latvia’s P. tritici-repentis population, while F129L and G137R mutations were absent. This study provided insight into P. tritici-repentis population’s sensitivity to active ingredients of DMI and OoI fungicide groups, helping to fill the knowledge gap about the pathogen fungicide sensitivity in this region. Full article

An advanced approach to the automated assessment of a microscopic slide containing spores is presented. The objective is to develop an intelligent system for the rapid and precise estimation of phytopathogenic spore concentration on microscopic slides, thereby enabling automated processing. The smart microscopy scanning system comprises an electronic microscope, a coordinate table, and software for the control of the coordinate table and image processing. The developed smart microscopy scanning system processes the entire microscope slide with multiple exposed strips, which are automatically determined based on the novel two-stage algorithm. The analysis of trained convolutional neural networks employed for the detection of spore phytopathogens demonstrates high precision and recall metrics. The system is capable of identifying and counting the number of spores of phytopathogenic fungi species Blumeria graminis, Puccinia striiformis, and Pyrenophora tritici-repentis on each exposed strip. A methodology for estimating the spore distribution on a microscopic slide is proposed, which involves calculating the average spore concentration density. Full article

Tan spot (Pyrenophora tritici-repentis) is presenting a persistent challenge to the plant health and yield of all wheat-growing regions. This research is focused on tan spot disease management in spring wheat when planted at three distinct times and with three different seeding rates without the use of fungicides. Across all years, higher seed rates (500 and 600 seeds per m²) generally resulted in lower tan spot intensity compared to the lower seed rate (400 seeds per m²). Significant differences in tan spot intensity were observed across seed rates at all sowing times. In 2021, the percentage of the AUDPC was significantly higher in the late sowing time (324.58%), with about a 2-fold difference compared with the early (167.48%) and optimal sowing time (191.80%). This suggests that delayed sowing significantly exacerbates disease occurrence. The combined effect of sowing time and year on the AUDPC was notably significant. The AUDPC of the tan spot in all seed rates was the highest in the late sowing time plots in comparison to the ideal and initial planting dates plots. Our results demonstrate how important seed rate and sowing timing are in determining the degree of tan spot in spring wheat. Growing crop methods may be improved by taking these elements into account to better control tan spots. More agricultural methods and environmental aspects should be investigated in future studies to create all-encompassing tan spot control plans. Full article

Ophibolin A, a fungal sesterterpene, exerts a pivotal influence in a diverse array of biological processes, encompassing herbicidal, bactericidal, fungicidal, and cytotoxic activities. Sixty genes associated with sesterterpene compound biosynthesis were obtained from Bipolaris eleusines via transcriptome sequencing, and those closely linked to ophiobolin A biosynthesis were subsequently filtered. A gene encoding 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR) that catalyzes the first committed step of ophiobolin biosynthesis in the mevalonic acid (MVA) pathway was isolated and characterized using RACE (Rapid Amplification of cDNA Ends) technology from ophiobolin A-producing fungus, B. eleusines. The full-length cDNA of the B. eleusines HMGR gene (BeHMGR) was 3906 bp and contained a 3474 bp open reading frame (ORF) encoding 1157 amino acids. Sequence analysis revealed that deduced BeHMGR had high homology to the known HMGRs from Pyrenophora tritici-repentis and Leptosphaeria maculans. It had a calculated molecular mass of about 124.65 kDa and an isoelectric point (pI) of 6.90. It contained two putative HMG-CoA-binding motifs and two NADP(H)-binding motifs. Induced expression analysis of the BeHMGR gene by methyl jasmonate treatment using quantitative fluorescence PCR showed that it significantly elevated after 3 h of methyl jasmonate treatment, peaked at 6 h, and then gradually decreased. This demonstrates that BeHMGR gene expression is induced by methyl jasmonate. Full 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. Full article

Leaf airborne diseases cause major shortfalls in agricultural crops. The introduction of technical means can significantly improve early-warning systems for plant diseases as well as provide timely and accurate forecasts. In this paper, we aim to evaluate the possibilities of detecting a phytopathogenic infection using a spore-catching device developed at the Federal Research Center of Biological Plant Protection (FRCBPP) on winter wheat varieties of different levels of susceptibility to major economically important leaf diseases, taking into account climatic conditions. The device captures spores in the surface layer of air among crop plants. We conducted research in the experimental fields of FRCBPP in 2019–2021. The objects of the study were four cultivars of winter wheat. They were selected according to the degree of resistance to various leaf diseases. We studied the progress of wheat diseases according to generally accepted international scales the onset of the first manifestations to their maximum development. We studied the aerogenic infection in wheat crops using the FRCBPP developed portable device for determining the infestation of plants. Sampling was carried out in the same period as the visual assessment. The samples were taken in the crops of each variety at five points. The sampling time was one minute. As a result of research on experimental crops of four varieties of winter wheat, we observed the development of such diseases as powdery mildew (Erysiphe graminis), yellow spot (Pyrenophora tritici-repentis), septoria leaf spot (Septoria tritici), yellow (Puccinia striiformis) and brown rust (Puccinia triticina). In a laboratory study of samples under a light microscope, all of the listed pathogens were found except for septoria leaf spot. Two-way analysis of variance confirmed the statistically significant separate and cumulative influence of the cultivar and year factor on winter wheat diseases. A generalized correlation analysis for three growing seasons (2019–2021) showed that an average statistically significant correlation coefficient (0.5–0.6) remains for the total groups for powdery mildew, yellow and brown rust. This indicator for the causative agent of yellow spot was equal to 0.4 with a high level of statistical significance. Thus, we conclude that by using a spore-catching device, it is possible to identify spores of economically significant pathogens in winter wheat crops and predict the further development of pathogens, taking into account the cultivar and annual climate factors. Full article

Pyrenophora tritici-repentis (Died.) Drechs., the causal agent of tan spot, is one of the most serious biotic diseases affecting wheat worldwide (Triticum aestivum L.). Studying the interaction between different fungicide mixtures and nitrogen (N) rates under tan spot outbreaks is of key importance for reducing aboveground biomass and grain yield losses. Taking this into account, our study took a mechanistic approach to estimating the combined effect of different fungicides and N fertilization schemes on the severity of tan spot, green leaf area index, SPAD index, aboveground biomass dynamics, and yield in a wheat crop affected at the reproductive stage. Our results indicated that reductions in green leaf area, healthy area duration (HAD), and the chlorophyll concentration (SPAD index) due to increases in the percentage of damage led to decreases in biomass production (−19.2%) and grain yield (−48.1%). Fungicides containing triazole + strobilurin + carboxamides (TSC) or triazole + strobilurin (TS) combined with high N doses showed the most efficient disease control. The positive physiological effects of TSC fungicides, such as extending the green leaf area, are probably responsible for the greater production of aboveground biomass (+29.3%), as well as the positive effects on grain yield (+15.8%) with respect to TS. Both fungicide treatments increased grains per spike, kernel weight, spikes m⁻², grains m⁻²_, and grain yield. The increase in biomass in the TSC tended to cause slighter non-significant increases in grains per spike, 1000-kernel weight and grain yield compared with TS. The linear regression revealed positive associations among the extension of HAD and biomass (+5.88 g.m⁻².HAD⁻¹.day⁻¹), grain yield (+38 kg.ha.HAD⁻¹.day⁻¹), and grain number (100.7 grains m².HAD⁻¹.day⁻¹), explained by the interactions of high N doses and fungicides. Our study is the first report of the positive effect of TSC fungicides with high N doses on grain yield related-traits under tan spot infections in wheat. Full article

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. Full article