scholarly journals A dispensable paralog of succinate dehydrogenase subunit C mediates standing resistance towards a subclass of SDHI fungicides inZymoseptoria tritici

2019 ◽  
Author(s):  
Diana Steinhauer ◽  
Marie Salat ◽  
Regula Frey ◽  
Andreas Mosbach ◽  
Torsten Luksch ◽  
...  
Keyword(s):  
Succinate Dehydrogenase ◽  
Rational Design ◽  
Population Genomics ◽  
Computational Modelling ◽  
Differential Sensitivity ◽  
Strong Impact ◽  
Zymoseptoria Tritici ◽  
C Subunit ◽  
Succinate Dehydrogenase Inhibitor

AbstractSuccinate dehydrogenase inhibitor (SDHI) fungicides are widely used for the control of a broad range of fungal diseases. This has been the most rapidly expanding fungicide group in terms of new molecules discovered and introduced for agricultural use over the past fifteen years. A particular pattern of differential sensitivity (resistance) to a subclass of chemically-related SDHIs (SHA-SDHIs) was observed in naïveZymoseptoria triticipopulations. Class specific SHA-SDHI resistance was confirmed at the enzyme level but did not correlate with the genotypes of the succinate dehydrogenase (SDH) encoding genes. Mapping and characterization of the genetic factor responsible for standing SHA-SDHI resistance in natural field isolates identified a gene (alt-SDHC) encoding a paralog of the C subunit of succinate dehydrogenase. This paralog was not present within our sensitive reference isolates and found at variable frequencies withinZ. triticipopulations. Using reverse genetics, we showed that alt-SDHC associates with the three other SDH subunits leading to a fully functional enzyme and that a unique Qp-site residue within the alt-SDHC protein confers SHA-SDHI resistance. Enzymatic assays, computational modelling and docking simulations for the two types of SQR enzymes (alt-SDHC, SDHC) enabled us to describe protein-inhibitor interactions at an atomistic level and to propose rational explanations for differential potency and resistance across SHA-SDHIs. EuropeanZ. triticipopulations displayed a presence (20-30%) / absence polymorphism ofalt-SDHC, as well as differences inalt-SDHCexpression levels and splicing efficiency. These polymorphisms have a strong impact on SHA-SDHI resistance phenotypes. Characterization of thealt-SDHCpromoter in EuropeanZ. triticipopulations suggest that transposon insertions are associated with the strongest resistance phenotypes. These results establish that a dispensable paralogous gene determines SHA-SDHIs fungicide resistance in natural populations ofZ. tritici. This study paves the way to an increased awareness of the role of fungicidal target paralogs in resistance to fungicides and demonstrates the paramount importance of population genomics in fungicide discovery.Author SummaryZymoseptoria triticiis the causal agent of Septoria tritici leaf blotch (STB) of wheat, the most devastating disease for cereal production in Europe. Multiple succinate dehydrogenase inhibitor (SDHI) fungicides have been developed and introduced for the control of STB. We report the discovery and detailed characterization of a paralog of the C subunit of the SDH enzyme conferring standing resistance towards a particular chemical subclass of the SDHIs. The resistance gene is characterized by its presence/absence, expression and splicing polymorphisms which in turn affect resistance levels. The identified mechanism influenced the chemical optimization phase which led to the discovery of pydiflumetofen, exemplifying the importance of population genomics for discovery and rational design of the most adapted solutions.

Sensitivity of Alternaria alternata from Citrus to Boscalid and Polymorphism in Iron-Sulfur and in Anchored Membrane Subunits of Succinate Dehydrogenase

Plant Disease ◽  
2015 ◽  
Vol 99 (2) ◽  
pp. 231-239 ◽  
Author(s):  
Byron Vega ◽  
Megan M. Dewdney
Keyword(s):  
Succinate Dehydrogenase ◽  
Alternaria Alternata ◽  
Mycelial Growth ◽  
Conidial Germination ◽  
Brown Spot ◽  
Sequence Comparisons ◽  
Sensitivity Tests ◽  
Alternaria Brown Spot ◽  
Succinate Dehydrogenase Inhibitor

Boscalid, a succinate dehydrogenase inhibitor (SDHI), was registered in 2011 to control Alternaria brown spot (ABS) of citrus, caused by Alternaria alternata. In this study, the effect of boscalid on mycelial growth, conidial germination, and resazurin reduction was established in a subset of 16 sensitive isolates using three different media. Conidial germination and mycelial growth inhibition were not suppressed even at higher concentrations of boscalid, although effective concentration to inhibit 50% growth (EC50) values were established with each method. Resazurin reduction produced the lowest EC50 values and was selected for further sensitivity tests. In total, 419 isolates, never exposed to boscalid and collected from Florida tangerine orchards between 1996 to 2012, were tested for boscalid sensitivity. The sensitivity distribution was a unimodal curve with a mean EC50 value of 0.60 μg/ml and a range of 0.07 to 5.84 μg/ml. The molecular characterization of the succinate dehydrogenase (SDH) genes were also determined in a subset of 15 isolates, exhibiting great variability in boscalid sensitivity, by cloning and sequencing the sdhB, sdhC, and sdhD genes. Sequence comparisons of the SDH complex revealed the presence of mutations in 14 of 15 isolates. In total, 21 mutations were identified. Double and multiple mutations were observed in SDHC and SDHD, respectively. In SDHB, 4 mutations were observed while, in SDHC and SDHD, 5 and 12 mutations were detected, respectively. No mutations were found in the highly conserved histidine residues at positions 277 in SDHB, 134 in SDHC, and 133 in SDHD, typically observed in SDHI-resistant isolates. Our findings suggest that A. alternata populations from Florida are sensitive to boscalid and it could be used in ABS spray programs. Boscalid resistance is currently not a problem, although further monitoring for resistance is advisable.

scholarly journals Comparison of fine-scale recombination maps in fungal plant pathogens reveals dynamic recombination landscapes and intragenic hotspots

2017 ◽  
Author(s):  
Eva H. Stukenbrock ◽  
Julien Y. Dutheil
Keyword(s):  
Recombination Rate ◽  
Plant Pathogens ◽  
Population Genomics ◽  
Gene Evolution ◽  
Strong Impact ◽  
Recombination Rates ◽  
Zymoseptoria Tritici ◽  
Sequence Composition ◽  
Recombination Hotspots ◽  
Fungal Plant Pathogens

AbstractMeiotic recombination is an important driver of evolution. Variability in the intensity of recombination across chromosomes can affect sequence composition, nucleotide variation and rates of adaptation. In many organisms recombination events are concentrated within short segments termed recombination hotspots. The variation in recombination rate and positions of recombination hotspot can be studied using population genomics data and statistical methods. In this study, we conducted population genomics analyses to address the evolution of recombination in two closely related fungal plant pathogens: the prominent wheat pathogen Zymoseptoria tritici and a sister species infecting wild grasses Zymoseptoria ardabiliae. We specifically addressed whether recombination landscapes, including hotspot positions, are conserved in the two recently diverged species and if recombination contributes to rapid evolution of pathogenicity traits. We conducted a detailed simulation analysis to assess the performance of methods of recombination rate estimation based on patterns of linkage disequilibrium, in particular in the context of high nucleotide diversity. Our analyses reveal overall high recombination rates, a lack of suppressed recombination in centromeres and significantly lower recombination rates on chromosomes that are known to be accessory. The comparison of the recombination landscapes of the two species reveals a strong correlation of recombination rate at the megabase scale, but little correlation at smaller scales. The recombination landscapes in both pathogen species are dominated by frequent recombination hotspots across the genome including coding regions, suggesting a strong impact of recombination on gene evolution. A significant but small fraction of these hotspots co-localize between the two species, suggesting that hotspots dynamics contribute to the overall pattern of fast evolving recombination in these species.

Characterization of pneumatic transportation of pulverised coal in a horizontal pipeline through measurement and computational modelling

Fuel ◽  
2009 ◽  
Vol 88 (12) ◽  
pp. 2348-2356 ◽  
Author(s):  
A. Chinnayya ◽  
A. Chtab ◽  
J.Q. Shao ◽  
R.M. Carter ◽  
Y. Yan ◽  
...  
Keyword(s):  
Computational Modelling ◽  
Pneumatic Transportation ◽  
Pulverised Coal

scholarly journals U.S. TREND INFLATION REINTERPRETED: THE ROLE OF FISCAL POLICIES AND TIME-VARYING NOMINAL RIGIDITIES

2014 ◽  
Vol 19 (6) ◽  
pp. 1294-1308 ◽  
Author(s):  
Nicola Acocella ◽  
Giovanni Di Bartolomeo ◽  
Patrizio Tirelli
Keyword(s):  
Strong Impact ◽  
Fiscal Policies ◽  
Time Varying ◽  
Nominal Rigidities ◽  
Distortionary Taxation ◽  
Trend Inflation ◽  
Wage Indexation ◽  
Joint Evolution

This paper offers a reinterpretation of the Fed's time-varying implicit inflation target, based on two considerations. The first is that the need to alleviate the burden of distortionary taxation may justify the choice of a positive inflation rate. The second is based on compelling evidence that the degree of price and wage indexation falls with trend inflation. In fact, we find that a proper characterization of the joint evolution of fiscal variables and nominal rigidities has a strong impact on the Ramsey optimal policies, implying optimal inflation dynamics that are consistent with the observed evolution of U.S. trend inflation. By contrast, tax policies have been too lax, especially at the time of the controversial Bush tax cuts.

Activity of A Novel Succinate Dehydrogenase Inhibitor Fungicide Pydiflumetofen against Fusarium fujikuroi causing Rice Bakanae Disease

Plant Disease ◽  
2021 ◽  
Author(s):  
Yang Bai ◽  
Chun-Yan Gu ◽  
Rui Pan ◽  
Muhammad Abid ◽  
Hao-Yu Zang ◽  
...  
Keyword(s):  
Cell Membrane ◽  
Succinate Dehydrogenase ◽  
Field Trials ◽  
Cell Membrane Permeability ◽  
Cross Resistance ◽  
Fusarium Fujikuroi ◽  
Control Efficacy ◽  
Bakanae Disease ◽  
Geographical Regions ◽  
Succinate Dehydrogenase Inhibitor

New fungicides are tools to manage fungal diseases and overcome emerging resistance in fugnal pathogens. In this study, a total of 121 isolates of Fusarium fujikuroi, the causal agent of rice bakanae disease (RBD), were collected from various geographical regions of China, and their sensitivity to a novel succinate dehydrogenase inhibitor (SDHI)fungicide ‘pydiflumetofen’ was evaluated. The 50% effective concentration (EC50) value of pydiflumetofen for mycelial growth suppression ranged from 0.0101 to 0.1012 μg/ml and for conidial germination inhibition ranged from 0.0051to 0.1082 μg/ml. Pydiflumetofen treated hyphae showed contortion and increased branching, cell membrane permeability, and glycerol content significantly. The result of electron microscope transmission indicated that pydiflumetofen damaged the mycelial cell wall and the cell membrane, and almost broken up the cells, which increased the intracellular plasma leakage. There was no cross-resistance between pydiflumetofen and the widely used fungicides such as carbendazim, prochloraz, and phenamacril. Pydiflumetofen was found safe to seeds and rice seedlings of four rice cultivars, used up to 400 μg/ml. Seed treatment significantly decreased the rate of diseased plants in the greenhouse as well as in field trials in 2017 and 2018. Pydiflumetofen showed superb results against RBD, when used at 10 or 20 g a.i./100 kg of treated seeds, providing over 90% control efficacy (the highest control efficacy was up to 97%), which was significantly higher than that of 25% phenamacril (SC) at 10g or carbendazim at 100 g. Pydiflumetofen is highly effective against F. fujikuroi growth and sporulation as well as RBD in the field.

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