scholarly journals Measuring splash-dispersal of a major wheat pathogen in the field

2021 ◽  
Author(s):  
Petteri Karisto ◽  
Frédéric Suffert ◽  
Alexey Mikaberidze
Keyword(s):  
Plant Pathogen ◽  
Precision Agriculture ◽  
Plant Pathogens ◽  
Population Based ◽  
Dispersal Kernel ◽  
Statistical Testing ◽  
Automated Image Analysis ◽  
Zymoseptoria Tritici ◽  
Phenotypic Data ◽  
Plant Pathosystems

AbstractCapacity for dispersal is a fundamental fitness component of plant pathogens. Empirical characterization of plant pathogen dispersal is of prime importance for understanding how plant pathogen populations change in time and space. We measured dispersal of Zymoseptoria tritici in natural environment. Primary disease gradients were produced by rain-splash driven dispersal and subsequent transmission via asexual pycnidiospores from infected source. To achieve this, we inoculated field plots of wheat (Triticum aestivum) with two distinct Z. tritici strains and a 50/50 mixture of the two strains. We measured effective dispersal of the Z. tritici population based on pycnidia counts using automated image analysis. The data were analyzed using a spatially-explicit mathematical model that takes into account the spatial extent of the source. We employed robust bootstrapping methods for statistical testing and adopted a two-dimensional hypotheses test based on the kernel density estimation of the bootstrap distribution of parameter values. Genotyping of re-isolated pathogen strains with strain-specific PCR-reaction further confirmed the conclusions drawn from the phenotypic data. The methodology presented here can be applied to other plant pathosystems.We achieved the first estimates of the dispersal kernel of the pathogen in field conditions. The characteristic spatial scale of dispersal is tens of centimeters – consistent with previous studies in controlled conditions. Our estimation of the dispersal kernel can be used to parameterize epidemiological models that describe spatial-temporal disease dynamics within individual wheat fields. The results have the potential to inform spatially targeted control of crop diseases in the context of precision agriculture.

scholarly journals Measuring splash-dispersal of a major wheat pathogen in the field

2021 ◽  
Author(s):  
Petteri Karisto ◽  
Frédéric Suffert ◽  
Alexey Mikaberidze
Keyword(s):  
Plant Pathogen ◽  
Plant Pathogens ◽  
Statistical Testing ◽  
Field Conditions ◽  
Automated Image Analysis ◽  
Accurate Estimation ◽  
Zymoseptoria Tritici ◽  
Phenotypic Data ◽  
Plant Disease Management ◽  
Dispersal Kernels

Capacity for dispersal is a fundamental fitness component of plant pathogens. Characterization of plant pathogen dispersal is important for understanding how pathogen populations change in time and space. We devised a systematic approach to measure and analyze rain splash-driven dispersal of plant pathogens in field conditions, using the major fungal wheat pathogen Zymoseptoria tritici as a case study. We inoculated field plots of wheat (Triticum aestivum) with two distinct Z. tritici strains. Next, we measured disease intensity as counts of fruiting bodies (pycnidia) using automated image analysis. These measurements characterized primary disease gradients, which we used to estimate effective dispersal of the pathogen population. Genotyping of re-isolated pathogen strains with strain-specific PCR-reaction confirmed the conclusions drawn from phenotypic data. Consistently with controlled environment studies, we found that the characteristic scale of dispersal is tens of centimeters. We analyzed the data using a spatially-explicit mathematical model that incorporates the spatial extent of the source, rather than assuming a point source, which allows for a more accurate estimation of dispersal kernels. We employed bootstrapping methods for statistical testing and adopted a two-dimensional hypotheses test based on kernel density estimation, enabling more robust inference compared to standard methods. We report the first estimates of dispersal kernels of the pathogen in field conditions. However, repeating the experiment in other environments would lead to more robust conclusions. We put forward advanced methodology that paves the way to further measurements of plant pathogen dispersal in field conditions, which can inform spatially targeted plant disease management.

scholarly journals Chromatin Dynamics Contribute to the Spatiotemporal Expression Pattern of Virulence Genes in a Fungal Plant Pathogen

mBio ◽  
2020 ◽  
Vol 11 (5) ◽  
Author(s):  
Lukas Meile ◽  
Jules Peter ◽  
Guido Puccetti ◽  
Julien Alassimone ◽  
Bruce A. McDonald ◽  
...  
Keyword(s):  
Plant Pathogen ◽  
Plant Pathogens ◽  
Chromatin Modifications ◽  
Zymoseptoria Tritici ◽  
Content Type ◽  
Spatiotemporal Expression ◽  
Effector Genes ◽  
Fungal Plant Pathogens ◽  
Fungal Plant Pathogen

ABSTRACT Dynamic changes in transcription profiles are key for the success of pathogens in colonizing their hosts. In many pathogens, genes associated with virulence, such as effector genes, are located in regions of the genome that are rich in transposable elements and heterochromatin. The contribution of chromatin modifications to gene expression in pathogens remains largely unknown. Using a combination of a reporter gene-based approach and chromatin immunoprecipitation, we show that the heterochromatic environment of effector genes in the fungal plant pathogen Zymoseptoria tritici is a key regulator of their specific spatiotemporal expression patterns. Enrichment in trimethylated lysine 27 of histone H3 dictates the repression of effector genes in the absence of the host. Chromatin decondensation during host colonization, featuring a reduction in this repressive modification, indicates a major role for epigenetics in effector gene induction. Our results illustrate that chromatin modifications triggered during host colonization determine the specific expression profile of effector genes at the cellular level and, hence, provide new insights into the regulation of virulence in fungal plant pathogens. IMPORTANCE Fungal plant pathogens possess a large repertoire of genes encoding putative effectors, which are crucial for infection. Many of these genes are expressed at low levels in the absence of the host but are strongly induced at specific stages of the infection. The mechanisms underlying this transcriptional reprogramming remain largely unknown. We investigated the role of the genomic environment and associated chromatin modifications of effector genes in controlling their expression pattern in the fungal wheat pathogen Zymoseptoria tritici. Depending on their genomic location, effector genes are epigenetically repressed in the absence of the host and during the initial stages of infection. Derepression of effector genes occurs mainly during and after penetration of plant leaves and is associated with changes in histone modifications. Our work demonstrates the role of chromatin in shaping the expression of virulence components and, thereby, the interaction between fungal pathogens and their plant hosts.

scholarly journals Evidence of Selection for Fungicide Resistance in Zymoseptoria tritici Populations on Wheat in Western Oregon

Plant Disease ◽  
2016 ◽  
Vol 100 (2) ◽  
pp. 483-489 ◽  
Author(s):  
Laura E. Hayes ◽  
Kathryn E. Sackett ◽  
Nicole P. Anderson ◽  
Michael D. Flowers ◽  
Christopher C. Mundt
Keyword(s):  
Fungicide Resistance ◽  
Fungal Pathogen ◽  
Plant Pathogens ◽  
Septoria Tritici Blotch ◽  
Septoria Tritici ◽  
Zymoseptoria Tritici ◽  
Resistance Evolution ◽  
Regional Control ◽  
Selection For ◽  
Moderately Resistant

Plant pathogens pose a major challenge to maintaining food security in many parts of the world. Where major plant pathogens are fungal, fungicide resistance can often thwart regional control efforts. Zymoseptoria tritici, causal agent of Septoria tritici blotch, is a major fungal pathogen of wheat that has evolved resistance to chemical control products in four fungicide classes in Europe. Compared with Europe, however, fungicide use has been less and studies of fungicide resistance have been infrequent in North American Z. tritici populations. Here, we confirm first reports of Z. tritici fungicide resistance evolution in western Oregon through analysis of the effects of spray applications of propiconazole and an azoxystrobin + propiconazole mixture during a single growing season. Frequencies of strobilurin-resistant isolates, quantified as proportions of G143A mutants, were significantly higher in azoxystrobin-sprayed plots compared with plots with no azoxystrobin treatment at two different locations and were significantly higher in plots of a moderately resistant cultivar than in plots of a susceptible cultivar. Thus, it appears that western Oregon Z. tritici populations have the potential to evolve levels of strobilurin resistance similar to those observed in Europe. Although the concentration of propiconazole required to reduce pathogen growth by 50% values were numerically greater for isolates collected from plots receiving propiconazole than in control plots, this effect was not significant (P > 0.05).

scholarly journals Extracellular vesicles from the apoplastic fungal wheat pathogen Zymoseptoria tritici

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Erin H. Hill ◽  
Peter S. Solomon
Keyword(s):  
Extracellular Vesicles ◽  
Fungal Pathogen ◽  
Plant Pathogens ◽  
Sequence Similarity ◽  
Protein Composition ◽  
Broth Culture ◽  
Zymoseptoria Tritici ◽  
Culture Filtrates ◽  
In Vitro Investigation

Abstract Background The fungal pathogen Zymoseptoria tritici is a significant constraint to wheat production in temperate cropping regions around the world. Despite its agronomic impacts, the mechanisms allowing the pathogen to asymptomatically invade and grow in the apoplast of wheat leaves before causing extensive host cell death remain elusive. Given recent evidence of extracellular vesicles (EVs)—secreted, membrane-bound nanoparticles containing molecular cargo—being implicated in extracellular communication between plants and fungal pathogen, we have initiated an in vitro investigation of EVs from this apoplastic fungal wheat pathogen. We aimed to isolate EVs from Z. tritici broth cultures and examine their protein composition in relation to the soluble protein in the culture filtrate and to existing fungal EV proteomes. Results Zymoseptoria tritici EVs were isolated from broth culture filtrates using differential ultracentrifugation (DUC) and examined with transmission electron microscopy (TEM) and nanoparticle tracking analysis (NTA). Z. tritici EVs were observed as a heterogeneous population of particles, with most between 50 and 250 nm. These particles were found in abundance in the culture filtrates of viable Z. tritici cultures, but not heat-killed cultures incubated for an equivalent time and of comparable biomass. Bottom-up proteomic analysis using LC–MS/MS, followed by stringent filtering revealed 240 Z. tritici EV proteins. These proteins were distinct from soluble proteins identified in Z. tritici culture filtrates, but were similar to proteins identified in EVs from other fungi, based on sequence similarity analyses. Notably, a putative marker protein recently identified in Candida albicans EVs was also consistently detected in Z. tritici EVs. Conclusion We have shown EVs can be isolated from the devastating fungal wheat pathogen Z. tritici and are similar to protein composition to previously characterised fungal EVs. EVs from human pathogenic fungi are implicated in virulence, but the role of EVs in the interaction of phytopathogenic fungi and their hosts is unknown. These in vitro analyses provide a basis for expanding investigations of Z. tritici EVs in planta, to examine their involvement in the infection process of this apoplastic wheat pathogen and more broadly, advance understanding of noncanonical secretion in filamentous plant pathogens.

scholarly journals At Least Two Origins of Fungicide Resistance in Grapevine Downy Mildew Populations

2007 ◽  
Vol 73 (16) ◽  
pp. 5162-5172 ◽  
Author(s):  
Wei-Jen Chen ◽  
François Delmotte ◽  
Sylvie Richard Cervera ◽  
Lisette Douence ◽  
Charles Greif ◽  
...  
Keyword(s):  
Plant Pathogen ◽  
Fungicide Resistance ◽  
Fungal Pathogens ◽  
Plant Pathogens ◽  
Plasmopara Viticola ◽  
Isolated Populations ◽  
Grapevine Downy Mildew ◽  
First Case ◽  
Wide Range ◽  
Pathogen Populations

ABSTRACT Quinone outside inhibiting (QoI) fungicides represent one of the most widely used groups of fungicides used to control agriculturally important fungal pathogens. They inhibit the cytochrome bc 1 complex of mitochondrial respiration. Soon after their introduction onto the market in 1996, QoI fungicide-resistant isolates were detected in field plant pathogen populations of a large range of species. However, there is still little understanding of the processes driving the development of QoI fungicide resistance in plant pathogens. In particular, it is unknown whether fungicide resistance occurs independently in isolated populations or if it appears once and then spreads globally by migration. Here, we provide the first case study of the evolutionary processes that lead to the emergence of QoI fungicide resistance in the plant pathogen Plasmopara viticola. Sequence analysis of the complete cytochrome b gene showed that all resistant isolates carried a mutation resulting in the replacement of glycine by alanine at codon 143 (G143A). Phylogenetic analysis of a large mitochondrial DNA fragment including the cytochrome b gene (2,281 bp) across a wide range of European P. viticola isolates allowed the detection of four major haplotypes belonging to two distinct clades, each of which contains a different QoI fungicide resistance allele. This is the first demonstration that a selected substitution conferring resistance to a fungicide has occurred several times in a plant-pathogen system. Finally, a high population structure was found when the frequency of QoI fungicide resistance haplotypes was assessed in 17 French vineyards, indicating that pathogen populations might be under strong directional selection for local adaptation to fungicide pressure.

scholarly journals Auxological and endocrine phenotype in a population-based cohort of patients with PROP1 gene defects

2005 ◽  
Vol 153 (3) ◽  
pp. 389-396 ◽  
Author(s):  
Jan Lebl ◽  
Jan Vosáhlo ◽  
Roland W Pfaeffle ◽  
Heike Stobbe ◽  
Jana Černá ◽  
...  
Keyword(s):  
Genomic Analysis ◽  
Population Based ◽  
Hormone Deficiency ◽  
Heterozygous Mutation ◽  
Pituitary Hormone ◽  
Phenotypic Analysis ◽  
Phenotypic Data ◽  
Sibling Pairs ◽  
Pituitary Development ◽  
Gene Defects

Objective: Multiple pituitary hormone deficiency (MPHD) may result from defects of transcription factors that govern early pituitary development. We aimed to establish the prevalence of HESX1, PROP1, and POU1F1 gene defects in a population-based cohort of patients with MPHD and to analyse the phenotype of affected individuals. Design and methods: Genomic analysis was carried out on 74 children and adults with MPHD from the Czech Republic (including four sibling pairs). Phenotypic data were collected from medical records and referring physicians. Results: One patient carried a heterozygous mutation of POU1F1 (71C > T), and 18 patients (including three sibling pairs) had a PROP1 mutation (genotypes 150delA/301delGA/9/, 301delGA/301-delGA/8/, or 301delGA/349T > A/1/). A detailed longitudinal phenotypic analysis was performed for patients with PROP1 mutations (n = 17). The mean ( ±s.d.) birth length SDS of these patients (0.12 ± 0.76) was lower than expected based on their mean ( ±s.d.) birth weight SDS (0.63 ± 1.27; P = 0.01). Parental heights were normal. The patients’ mean ( ±s.d.) height SDS declined to −1.5 ± 0.9, −3.6 ± 1.3 and −4.1 ± 1.2 at 1.5, 3 and 5 years of age, respectively. GH therapy, initiated at 6.8 ± 3.2 years of age (mean dose: 0.022 mg/kg per day), led to substantial growth acceleration in all patients. Mean adult height (n = 7) was normal when adjusted for mid-parental height. ACTH deficiency developed in two out of seven young adult patients. Conclusions: PROP1 defects are a prevalent cause of MPHD. We suggest that testing for PROP1 mutations in patients with MPHD might become standard practice in order to predict risk of additional pituitary hormone deficiencies.

An Overhead Optical Yield Monitor for a Sugarcane Harvester Based on Two Optical Distance Sensors Mounted above the Loading Elevator

2017 ◽  
Vol 33 (5) ◽  
pp. 687-693 ◽  
Author(s):  
Randy R. Price ◽  
Richard M. Johnson ◽  
Ryan P. Viator
Keyword(s):  
Precision Agriculture ◽  
Statistical Testing ◽  
Coefficient Of Determination ◽  
Power Type ◽  
Type Curve ◽  
Yield Monitor ◽  
Sugarcane Harvester ◽  
Material Length ◽  
Yield Monitoring

Abstract. A yield monitor was constructed for a billet-type sugarcane harvester that uses two laser distance sensors mounted above the loading elevator to measure the height and length of the billet piles per slat. By using this method, a volume-to-mass relationship can be established for the weight flow of sugarcane through the combine for the measurement of yield. Testing of the system indicated that the cumulative billet pile length had the best relationship to harvested weight with a linear line relationship and coefficients of determinations ranging from 0.93 and 0.97. Estimated yields matched actual yields very well with a 0.99 slope and a coefficient of determination of 0.87 and yields were predicted to be within 7.3 metric tons/ha of actual values. Material height did not perform as well as material length and exhibited a power-type curve relationship to harvested weight with coefficients of determination ranging from 0.66 to 0.93, and estimated yields only matched actual yields with a coefficient of determination of 0.46. A third parameter, the product of material height to material length, also returned a power-type curve relationship to harvested weight with coefficients of determination ranging from 0.74 to 0.96 and yield comparisons for this parameter achieved a coefficient of determination of 0.74 which was better than the material height alone, but not as good as material length by itself. Statistical testing indicated that variances in material length were strongly correlated to material flow, but not to sugarcane variety, direction of cut, nor day of testing. Sample analysis indicated that the monitor can predict yields to within 2.2 metric tons/ha of actual values on 0.4 ha (or larger) precision farming blocks. Installation times were fast, easy, and can be performed in the field with little changes to the combine as the sensor bar merely clamps to the upper rails of the elevator. This yield monitoring system may provide yield monitoring in sugarcane on a per field basis that is easy-to-mount, non-contact, and robust from dirt and debris. Keywords: GPS, Harvesting, Precision agriculture, Sugarcane, Yield monitor.

scholarly journals Direct Visualization of Cystic Fibrosis Transmembrane Regulator Mutations in the Clinical Laboratory Setting

2004 ◽  
Vol 50 (5) ◽  
pp. 836-845 ◽  
Author(s):  
Charles M Strom ◽  
David D Clark ◽  
Feras M Hantash ◽  
Larry Rea ◽  
Ben Anderson ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Multiplex Pcr ◽  
High Throughput ◽  
Clinical Laboratory ◽  
Regulatory Gene ◽  
Population Based ◽  
Dna Chip ◽  
Automated Image Analysis ◽  
Nucleotide Polymorphisms ◽  
Technical Validation

Abstract Background: The recommendation for population- based cystic fibrosis (CF) carrier screening by the American College of Medical Genetics for the 25 most prevalent mutations and 6 polymorphisms in the CF transmembrane regulatory gene has greatly increased clinical laboratory test volumes. We describe the development and technical validation of a DNA chip in a 96-well format to allow for high-throughput genotype analysis. Methods: The CF Portrait™ chip contains an 8 × 8 array of capture probes and controls to detect all requisite alleles. Single-tube multiplex PCR with 15 biotin-labeled primer pairs was used to amplify sequences containing all single-nucleotide polymorphisms to be interrogated. Detection of a thin-film signal created by hybridization of multiplex PCR-amplified DNA to complementary capture probes was performed with an automated image analysis instrument, NucleoSight™. Allele classification, data formatting, and uploading to a laboratory information system were fully automated. Results: The described platform correctly classified all mutations and polymorphisms and can screen ∼1300 patient samples in a 10-h shift. Final validation was performed by two separate 1000-sample comparisons with Roche CF Gold line probe strips and the Applera CF OLA, Ver 3.0. The CF Portrait Biochip made no errors during this validation, whereas the Applera assay made seven miscalls of the IVS-8 5T/7T/9T polymorphism Conclusions: The CF Portrait platform is an automated, high-throughput, DNA chip-based assay capable of accurately classifying all CF mutations in the recommended screening panel, including the IVS-8 5T/7T/9T polymorphism.

scholarly journals Emergence of Resistance to Fungicides: The Role of Fungicide Dose

2017 ◽  
Vol 107 (5) ◽  
pp. 545-560 ◽  
Author(s):  
Alexey Mikaberidze ◽  
Neil Paveley ◽  
Sebastian Bonhoeffer ◽  
Frank van den Bosch
Keyword(s):  
Dose Response ◽  
Plant Pathogens ◽  
Resistant Mutant ◽  
Emergence Time ◽  
Zymoseptoria Tritici ◽  
Antimicrobial Drugs ◽  
Response Data ◽  
Fungal Plant Pathogens ◽  
Resistant Mutants ◽  
High Doses

Resistance to antimicrobial drugs allows pathogens to survive drug treatment. The time taken for a new resistant mutant to reach a population size that is unlikely to die out by chance is called “emergence time.” Prolonging emergence time would delay loss of control. We investigate the effect of fungicide dose on the emergence time in fungal plant pathogens. A population dynamical model is combined with dose-response data for Zymoseptoria tritici, an important wheat pathogen. Fungicides suppress sensitive pathogen population. This has two effects. First, the rate of appearance of resistant mutants is reduced, hence the emergence takes longer. Second, more healthy host tissue becomes available for resistant mutants, increasing their chances to invade and accelerates emergence. In theory, the two competing effects may lead to a non-monotonic dependence of the emergence time on fungicide dose that exhibits a minimum. But according to field data, fungicides are unable to reduce the fungicide-sensitive population strongly enough even at high doses. Hence, for full resistance over realistic ranges of pathogen’s life history and fungicide dose-response parameters, emergence time decreases monotonically with increasing dose. For partial resistance, there can be cases within a limited parameter range, when emergence decelerates at higher doses.

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