Host Resistance and Temperature-Dependent Evolution of Aggressiveness in the Plant Pathogen Zymoseptoria tritici

Plasmopara viticola is a biotrophic pathogenic oomycete responsible for grapevine downy mildew. We present here the first draft of the P. viticola genome. Analysis of this sequence will help in understanding plant-pathogen interactions in oomycetes, especially pathogen host specialization and adaptation to host resistance.

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

10.1101/2021.03.23.436423 ◽

2021 ◽

Cited By ~ 1

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.

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Patterns of thermal adaptation in a worldwide plant pathogen: local diversity and plasticity reveal two-tier dynamics

10.1101/2019.12.16.877696 ◽

2019 ◽

Author(s):

Anne-Lise Boixel ◽

Michaël Chelle ◽

Frédéric Suffert

Keyword(s):

Plant Pathogen ◽

Natural Populations ◽

Thermal Adaptation ◽

Thermal Conditions ◽

List Type ◽

Zymoseptoria Tritici ◽

Local Conditions ◽

Temperature Conditions ◽

Spatiotemporal Scales ◽

Pathogen Populations

SummaryPlant pathogen populations inhabit patchy environments with contrasting, variable thermal conditions. We investigated the diversity of thermal responses in populations sampled over contrasting spatiotemporal scales, to improve our understanding of their dynamics of adaptation to local conditions.Samples of natural populations of the wheat pathogen Zymoseptoria tritici were collected from sites within the Euro-Mediterranean region subject to a broad range of environmental conditions. We tested for local adaptation, by accounting for the diversity of responses at the individual and population levels on the basis of key thermal performance curve parameters and ‘thermotype’ (groups of individuals with similar thermal responses) composition.The characterisation of phenotypic responses and genotypic structure revealed: (i) a high degree of individual plasticity and variation in sensitivity to temperature conditions across spatiotemporal scales and populations; (ii) geographic adaptation to local mean temperature conditions, with major alterations due to seasonal patterns over the wheat-growing season.The seasonal shifts in functional composition suggest that populations are locally structured by selection, contributing to shape adaptation patterns. Further studies combining selection experiments and modelling are required to determine how functional group selection drives population dynamics and adaptive potential in response to thermal heterogeneity.

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

PhytoFrontiers™ ◽

10.1094/phytofr-05-21-0039-r ◽

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.

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Evolution and Plasticity of the Transcriptome Under Temperature Fluctuations in the Fungal Plant Pathogen Zymoseptoria tritici

Frontiers in Microbiology ◽

10.3389/fmicb.2020.573829 ◽

2020 ◽

Vol 11 ◽

Author(s):

Arthur J. Jallet ◽

Arnaud Le Rouzic ◽

Anne Genissel

Keyword(s):

Plant Pathogen ◽

Temperature Fluctuations ◽

Zymoseptoria Tritici ◽

Fungal Plant Pathogen

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Quantification of In Planta Zymoseptoria tritici Progression Through Different Infection Phases and Related Association with Components of Aggressiveness

Phytopathology ◽

10.1094/phyto-09-19-0339-r ◽

2020 ◽

Vol 110 (6) ◽

pp. 1208-1215 ◽

Cited By ~ 2

Author(s):

Atikur Rahman ◽

Fiona Doohan ◽

Ewen Mullins

Keyword(s):

Growth Rate ◽

Latent Period ◽

Host Resistance ◽

Infection Process ◽

Early Infection ◽

Septoria Tritici Blotch ◽

Septoria Tritici ◽

In Planta ◽

Zymoseptoria Tritici ◽

Host Interaction

In planta growth of Zymoseptoria tritici, causal agent of Septoria tritici blotch of wheat, during the infection process has remained an understudied topic due to the long symptomless latent period before the emergence of fruiting bodies. In this study, we attempted to understand the relationship between in planta growth of Z. tritici relative to the primary components of aggressiveness, i.e., latent period and pycnidia coverage in regard to contrasting host resistance. We tested isolates collected from Ireland against the susceptible cultivar Gallant and cultivar Stigg, which has strong partial resistance. A clear isolate−host interaction effect (F = 3.018; P = 0.005, and F = 6.008; P < 0.001) for latent period and pycnidia coverage, respectively, was identified. Furthermore, during the early infection phase of latency from 5 to 11 days postinoculation (dpi), in planta growth rate of fungal biomass was significantly (F = 30.06; P < 0.001) more affected by host resistance than isolate specificity (F = 1.27; P = 0.27), indicating the importance of host resistance in the early infection phase. In planta Z. tritici growth rates in cultivar Gallant spiked between 11 and 16 dpi followed by a continuous fall onward, whereas in cultivar Stigg it was slowly progressive in nature. From correlation and regression analysis, we found that the in planta growth rate preceding the average latent period of cultivar Gallant has more influence on latency duration and pycnidia production. Likewise, correlation between component of aggressiveness and in planta growth rate of pathogen supports our understanding of aggressiveness to be driven by the pathogen’s multiplication capacity within host tissue.

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Ago1 Affects the Virulence of the Fungal Plant Pathogen Zymoseptoria tritici

Genes ◽

10.3390/genes12071011 ◽

2021 ◽

Vol 12 (7) ◽

pp. 1011

Author(s):

Michael Habig ◽

Klaas Schotanus ◽

Kim Hufnagel ◽

Petra Happel ◽

Eva H. Stukenbrock

Keyword(s):

Plant Pathogen ◽

Allelic Diversity ◽

Rnai Pathway ◽

Chromosome Stability ◽

In Planta ◽

Zymoseptoria Tritici ◽

Rnai Machinery ◽

Fungal Plant Pathogen ◽

Host Infection

In host-pathogen interactions RNA interference (RNAi) has emerged as a pivotal mechanism to modify both, the immune responses of the host as well as the pathogenicity and virulence of the pathogen. In addition, in some fungi RNAi is also known to affect chromosome biology via its effect on chromatin conformation. Previous studies reported no effect of the RNAi machinery on the virulence of the fungal plant pathogen Zymoseptoria tritici however the role of RNAi is still poorly understood in this species. Herein, we elucidate whether the RNAi machinery is conserved within the genus Zymoseptoria. Moreover, we conduct functional analyses of Argonaute and Dicer-like proteins and test if the RNAi machinery affects chromosome stability. We show that the RNAi machinery is conserved among closely related Zymoseptoria species while an exceptional pattern of allelic diversity was possibly caused by introgression. The deletion of Ago1 reduced the ability of the fungus to produce asexual propagules in planta in a quantitative matter. Chromosome stability of the accessory chromosome of Z. tritici was not prominently affected by the RNAi machinery. These results indicate, in contrast to previous finding, a role of the RNAi pathway during host infection, but not in the stability of accessory chromosomes in Z. tritici.

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

mBio ◽

10.1128/mbio.02343-20 ◽

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.

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Adaptation of a plant pathogen to partial host resistance: selection for greater aggressiveness in grapevine downy mildew

Evolutionary Applications ◽

10.1111/eva.12368 ◽

2016 ◽

Vol 9 (5) ◽

pp. 709-725 ◽

Cited By ~ 38

Author(s):

Chloé E. L. Delmas ◽

Frédéric Fabre ◽

Jérôme Jolivet ◽

Isabelle D. Mazet ◽

Sylvie Richart Cervera ◽

...

Keyword(s):

Downy Mildew ◽

Plant Pathogen ◽

Host Resistance ◽

Grapevine Downy Mildew ◽

Resistance Selection ◽

Selection For

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Effects of Microelements on Downy Mildew (Peronospora belbahrii) of Sweet Basil

Plants ◽

10.3390/plants10091793 ◽

2021 ◽

Vol 10 (9) ◽

pp. 1793

Author(s):

Yigal Elad ◽

Ziv Nisan ◽

Ziv Kleinman ◽

Dalia Rav-David ◽

Uri Yermiyahu

Keyword(s):

Field Experiment ◽

Downy Mildew ◽

Plant Pathogen ◽

Host Resistance ◽

Mode Of Action ◽

Sweet Basil ◽

Potted Plants ◽

Mixture Treatment ◽

Disease Reduction ◽

Irrigation Solution

We recently demonstrated that spraying or irrigating with Ca, Mg and K reduces the severity of sweet basil downy mildew (SBDM). Here, the effects of Mn, Zn, Cu and Fe on SBDM were tested in potted plants. The effects of Mn and Zn were also tested under semi-commercial and commercial-like field conditions. Spray applications of a mixture of EDTA-chelated microelements (i.e., Fe-EDTA, Mn-EDTA, Zn-EDTA, Cu-EDTA and Mo) reduces SBDM severity. The application of EDTA chelates of individual microelements (i.e., Fe-EDTA, Mn-EDTA and Zn-EDTA) significantly reduces SBDM in potted plants. Foliar applications of Mn-EDTA and Zn-EDTA are found to be effective under semi-commercial conditions and were, thus, further tested under commercial-like conditions. Under commercial-like conditions, foliar-applied Mn-EDTA and Zn-EDTA decreased SBDM severity by 46–71%. When applied through the irrigation solution, those two microelements reduce SBDM by more than 50%. Combining Mg with Mn-EDTA and Zn-EDTA in the irrigation solution does not provide any additional disease reduction. In the commercial-like field experiment, the microelement-mixture treatment, applied as a spray or via the irrigation solution, was combined with fungicides spray treatments. This combination provides synergistic disease control. The mode of action in this plant–pathogen system may involve features of altered host resistance.

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