scholarly journals Cross-resistance of the pathogenic fungus Alternaria alternata to fungicides with unrelated modes of action

2019 ◽  
Author(s):  
Li-Na Yang ◽  
Meng-Han He ◽  
Hai-Bing Ouyang ◽  
Wen Zhu ◽  
Zhe-Chao Pan ◽  
...  
Keyword(s):  
Human Health ◽  
Alternaria Alternata ◽  
Mode Of Action ◽  
Pathogenic Fungus ◽  
Positive Association ◽  
Cross Resistance ◽  
Strong Positive Correlation ◽  
Antimicrobial Compound ◽  
Modes Of Action ◽  
Sole Criterion

Abstract Background Cross-resistance, a phenomenon that a pathogen resists to one antimicrobial compound also resists to one or several other compounds, is one of major threats to human health and sustainable food production. It usually occurs among antimicrobial compounds sharing the mode of action. In this study, we determined the sensitivity profiles of Alternaria alternata, a fungal pathogen which can cause diseases in many crops to two fungicides (mancozeb and difenoconazole) with unrelated mode of action using a large number of isolates (234) collected from seven potato fields across China. Results We found that pathogens could also develop cross resistance to fungicides with different modes of action as indicated by a strong positive correlation between mancozeb and difenoconazole tolerances to A. alternata. We also found a positive association between mancozeb tolerance and aggressiveness of A. alternata, suggesting no fitness penalty of developing mancozeb resistance in the pathogen and hypothesize that mechanisms such as antimicrobial compound efflux and detoxification that limit intercellular accumulation of natural/synthetic chemicals in pathogens might account for the cross-resistance and the positive association between pathogen aggressiveness and mancozeb tolerance. Conclusions The detection of cross-resistance among different classes of fungicides suggests that the mode of action alone may not be an adequate sole criterion to determine what components to use in the mixture and/or rotation of fungicides in agricultural and medical sects. Similarly, the occurrence of a positive association between the pathogen’s aggressiveness and tolerance to mancozeb suggests that one unforeseen consequence of intensive application of site non-specific fungicides might be selection for enhanced aggressiveness in pathogen populations, thereby posing a greater threat to agricultural production and human health. In this case, the use of evolutionary principles in closely monitoring populations and the use of appropriate fungicide applications are important for effective use of the fungicides and durable infectious disease management.

scholarly journals Cross-resistance of the pathogenic fungus Alternaria alternata to fungicides with different modes of action

2019 ◽  
Author(s):  
Li-Na Yang ◽  
Meng-Han He ◽  
Hai-Bing Ouyang ◽  
Wen Zhu ◽  
Zhe-Chao Pan ◽  
...  
Keyword(s):  
Human Health ◽  
Alternaria Alternata ◽  
Mode Of Action ◽  
Pathogenic Fungus ◽  
Positive Association ◽  
Cross Resistance ◽  
Strong Positive Correlation ◽  
Antimicrobial Compound ◽  
Modes Of Action ◽  
Sole Criterion

Abstract Background: Cross-resistance, a phenomenon that a pathogen resists to one antimicrobial compound also resists to one or several other compounds, is one of major threats to human health and sustainable food production. It usually occurs among antimicrobial compounds sharing the mode of action. In this study, we determined the sensitivity profiles of Alternaria alternata , a fungal pathogen which can cause diseases in many crops to two fungicides (mancozeb and difenoconazole) with different mode of action using a large number of isolates (234) collected from seven potato fields across China. Results: We found that pathogens could also develop cross resistance to fungicides with different modes of action as indicated by a strong positive correlation between mancozeb and difenoconazole tolerances to A. alternata . We also found a positive association between mancozeb tolerance and aggressiveness of A. alternata , suggesting no fitness penalty of developing mancozeb resistance in the pathogen and hypothesize that mechanisms such as antimicrobial compound efflux and detoxification that limit intercellular accumulation of natural/synthetic chemicals in pathogens might account for the cross-resistance and the positive association between pathogen aggressiveness and mancozeb tolerance. Conclusions: The detection of cross-resistance among different classes of fungicides suggests that the mode of action alone may not be an adequate sole criterion to determine what components to use in the mixture and/or rotation of fungicides in agricultural and medical sects. Similarly, the observation of a positive association between the pathogen’s aggressiveness and tolerance to mancozeb suggests that intensive application of site non-specific fungicides might simultaneously lead to reduced fungicide resistance and enhanced ability to cause diseases in pathogen populations, thereby posing a greater threat to agricultural production and human health. In this case, the use of evolutionary principles in closely monitoring populations and the use of appropriate fungicide applications are important for effective use of the fungicides and durable infectious disease management.

scholarly journals Cross-resistance of the pathogenic fungus Alternaria alternata to fungicides with different modes of action

2019 ◽  
Author(s):  
Li-Na Yang ◽  
Meng-Han He ◽  
Hai-Bing Ouyang ◽  
Wen Zhu ◽  
Zhe-Chao Pan ◽  
...  
Keyword(s):  
Human Health ◽  
Alternaria Alternata ◽  
Mode Of Action ◽  
Pathogenic Fungus ◽  
Positive Association ◽  
Cross Resistance ◽  
Strong Positive Correlation ◽  
Antimicrobial Compound ◽  
Modes Of Action ◽  
Sole Criterion

Abstract Background: Cross-resistance, a phenomenon that a pathogen resists to one antimicrobial compound also resists to one or several other compounds, is one of major threats to human health and sustainable food production. It usually occurs among antimicrobial compounds sharing the mode of action. In this study, we determined the sensitivity profiles of Alternaria alternata , a fungal pathogen which can cause diseases in many crops to two fungicides (mancozeb and difenoconazole) with different mode of action using a large number of isolates (234) collected from seven potato fields across China. Results: We found that pathogens could also develop cross resistance to fungicides with different modes of action as indicated by a strong positive correlation between mancozeb and difenoconazole tolerances to A. alternata . We also found a positive association between mancozeb tolerance and aggressiveness of A. alternata , suggesting no fitness penalty of developing mancozeb resistance in the pathogen and hypothesize that mechanisms such as antimicrobial compound efflux and detoxification that limit intercellular accumulation of natural/synthetic chemicals in pathogens might account for the cross-resistance and the positive association between pathogen aggressiveness and mancozeb tolerance. Conclusions: The detection of cross-resistance among different classes of fungicides suggests that the mode of action alone may not be an adequate sole criterion to determine what components to use in the mixture and/or rotation of fungicides in agricultural and medical sects. Similarly, the observation of a positive association between the pathogen’s aggressiveness and tolerance to mancozeb suggests that intensive application of site non-specific fungicides might simultaneously lead to reduced fungicide resistance and enhanced ability to cause diseases in pathogen populations, thereby posing a greater threat to agricultural production and human health. In this case, the use of evolutionary principles in closely monitoring populations and the use of appropriate fungicide applications are important for effective use of the fungicides and durable infectious disease management.

scholarly journals Cross-resistance of the pathogenic fungus Alternaria alternata to fungicides with different modes of action

2019 ◽  
Vol 19 (1) ◽  
Author(s):  
Li-Na Yang ◽  
Meng-Han He ◽  
Hai-Bing Ouyang ◽  
Wen Zhu ◽  
Zhe-Chao Pan ◽  
...  
Keyword(s):  
Alternaria Alternata ◽  
Pathogenic Fungus ◽  
Cross Resistance ◽  
Modes Of Action

Resistance of Kochia (Kochia scoparia) to Sulfonylurea and Imidazolinone Herbicides

1990 ◽  
Vol 4 (1) ◽  
pp. 169-172 ◽  
Author(s):  
Michael M. Primiani ◽  
Josephine C. Cotterman ◽  
Leonard L. Saari
Keyword(s):  
Methyl Ester ◽  
Mode Of Action ◽  
Cross Resistance ◽  
Kochia Scoparia ◽  
Wheat Field ◽  
Modes Of Action ◽  
Imidazolinone Herbicides ◽  
Postemergence Herbicides ◽  
Greenhouse Tests

A biotype of kochia resistant to chlorsulfuron has been isolated from a Kansas wheat field that had been treated with chlorsulfuron for five consecutive years. In greenhouse tests, the biotype also was resistant to both preemergence and postemergence herbicides with the same mode of action including imazapyr, CGA-131036, the methyl ester of metsulfuron, DPX-M6316, DPX-L5300, and the methyl ester of sulfometuron. The degree of cross resistance varied among the herbicides tested. Herbicides with different modes of action, including atrazine, bromoxynil, MCPA, and diuron, effectively controlled the resistant biotype in the greenhouse.

Mutations in Sdh Gene Subunits Confer Different Cross Resistance Patterns to SDHI Fungicides in Alternaria alternata Causing Alternaria Leaf Spot of Almond in California

Plant Disease ◽  
2022 ◽  
Author(s):  
Helga Forster ◽  
Yong Luo ◽  
Lingling Hou ◽  
James Adaskaveg
Keyword(s):  
Alternaria Alternata ◽  
Leaf Spot ◽  
Mode Of Action ◽  
Molecular Mechanisms ◽  
Cross Resistance ◽  
Dilution Method ◽  
Common Disease ◽  
Common Mutation ◽  
Alternaria Leaf Spot ◽  
Wide Range

Alternaria leaf spot caused by Alternaria alternata and A. arborescens is a common disease of almond in California. Succinate dehydrogenase inhibitors (SDHIs) are widely used for its management, however, we observed reduced performance of SDHI fungicides at some field sites. Thus, we evaluated the sensitivity of 520 isolates of the main pathogen A. alternata from major production areas collected between 2006 and 2019 to boscalid and of a subset of 204 isolates to six members of the SDHIs belonging to six sub-groups. Additionally, 97 isolates (14 sensitive and 83 with reduced sensitivity) of the 204 were used to determine the molecular mechanisms of resistance. A wide range of in vitro concentrations to effectively inhibit mycelial growth by 50% (EC50 values) was determined for each fungicide using the spiral gradient dilution method. Some isolates were highly resistant (EC50 values >10 μg/ml) to boscalid (a pyridine-carboxamide), pyraziflumid (a pyrazine-carboxamide), and fluxapyroxad (a pyrazole-4-carboxamide), but not to fluopyram (a pyridinyl-ethyl-benzamide), isofetamid (a phenyl-oxo-ethyl thiophene amide), and pydiflumetofen (a N-methoxy-(phenyl-ethyl)-pyrazole-carboxamide). There was no strong cross resistance among the fungicides tested, including for the two pyrazole-4-carboxamides fluxapyroxad and penthiopyrad (tested for 33 of the 204 isolates). The comparison of EC50 values for fluopyram and isofetamid resulted in the highest coefficient of determination (R2 = 0.582) among ten pairwise comparisons between sub-groups. Sequence analyses of the 97 isolates revealed five mutations in SdhB, SdhC, or SdhD subunits of the Sdh target gene among 73 isolates with reduced sensitivity to at least one SDHI. No mutations were detected in the 14 sensitive isolates and in 10 of the 83 isolates with reduced sensitivity. The most common mutation (59 isolates) was H134R in SdhC. Other mutations included H277Y (8 isolates) and H277L (2 isolates) in SdhB, as well as G79R (2 isolates) and S135R (2 isolates) in SdhC. Mutations H277Y in SdhB and S135R in SdhC were only present in isolates collected in 2012 or earlier. Both conferred mostly high levels of resistance to boscalid and also reduced sensitivity to pyraziflumid, fluxapyroxad, and isofetamid with intermediate EC50 levels. Mutations H277L in SdhB, as well as H134R and G79R in SdhC, that were found in isolates obtained after 2012 had very similar resistance phenotypes with different levels of resistance to boscalid, pyraziflumid, and fluxapyroxad, whereas sensitivity to fluopyram, isofetamid, and pydiflumetofen was mostly less affected. Our data for SDHI fungicides do not support the classical concept of positive cross resistance within a single mode of action. Because some mutations conferred resistance to multiple SDHI sub-groups, however, resistance management needs to consider all SDHIs as a homogenous group that should be mixed or rotated with other modes of action prior to resistance development to either mode of action.

Probiotics for Gastrointestinal Health and�General�Wellbeing

2019 ◽  
Vol 15 (1) ◽  
pp. 22-29
Author(s):  
E.O. Irokanulo ◽  
M.A. Akalegbere
Keyword(s):  
Human Health ◽  
Low Income ◽  
Environmental Conditions ◽  
Mode Of Action ◽  
World Wide ◽  
Gut Flora ◽  
Gastrointestinal Infections ◽  
Gastrointestinal Health ◽  
Rural Settings ◽  
General Wellbeing

Gastrointestinal health is a precursor to general wellbeing in humans. Maintaining good normal gut flora for the health benefits they provide is important. Unfortunately, however, the good gut flora is sometimes dislodged during feeding and treatment with certain drugs. Foods that lead to such gut flora displacement may contain other microorganisms whose actions create unfavourable environmental conditions for resident flora. The principle of removing unwanted harmful gut flora; introducing good microorganisms through ingestion of live microorganisms, known as probiotics or foods that contain specific live microbes of interest is now practiced. Consumption of foods containing probiotics has long been practiced world-wide especially in rural settings and in low-income economies even though such consumptions may be unintended. Presently, careful isolation, characterization and testing of candidate probiotic organisms, has become the norm. This re-emerging phenomenon and the great impact it has on human health is considered here looking at probiotic sources; including foods, the role they play in gastrointestinal health, their mode of action and the disease types where they are beneficial to man including their safety and how their introduction in the �medical menu� in low-income nations can help in combating the rather very �regular� gastrointestinal infections in these countries.

scholarly journals Biochemical and molecular characterization of Alternaria alternata isolates highly resistant to procymidone from broccoli and cabbage

2021 ◽  
Vol 3 (1) ◽  
Author(s):  
Bingran Wang ◽  
Tiancheng Lou ◽  
Lingling Wei ◽  
Wenchan Chen ◽  
Longbing Huang ◽  
...  
Keyword(s):  
Alternaria Alternata ◽  
Single Point ◽  
Sodium Dodecyl ◽  
Cross Resistance ◽  
Molecular Characteristics ◽  
Single Point Mutation ◽  
Wide Range ◽  
Significant Difference ◽  
Leaf Blights ◽  
High Level

AbstractAlternaria alternata, a causal agent of leaf blights and spots on a wide range of hosts, has a high risk of developing resistance to fungicides. Procymidone, a dicarboximide fungicide (DCF), has been widely used in controlling Alternaria leaf blights in China for decades. However, the resistance of A. alternata against DCFs has rarely been reported from crucifer plants. A total of 198 A. alternata isolates were collected from commercial fields of broccoli and cabbage during 2018–2019, and their sensitivities to procymidone were determined. Biochemical and molecular characteristics were subsequently compared between the high-level procymidone-resistant (ProHR) and procymidone-sensitive (ProS) isolates, and also between ProHR isolates from broccoli and cabbage. Compared with ProS isolates, the mycelial growth rate, sporulation capacity and virulence of most ProHR isolates were reduced; ProHR isolates displayed an increased sensitivity to osmotic stresses and a reduced sensitivity to sodium dodecyl sulfate (SDS); all ProHR isolates showed a reduced sensitivity to hydrogen peroxide (H2O2) except for the isolate B102. Correlation analysis revealed a positive cross-resistance between procymidone and iprodione, or fludioxonil. When treated with 10 μg/mL of procymidone, both mycelial intracellular glycerol accumulations (MIGAs) and relative expression of AaHK1 in ProS isolates were higher than those in ProHR isolates. Sequence alignment of AaHK1 from ten ProHR isolates demonstrated that five of them possessed a single-point mutation (P94A, V612L, E708K or Q924STOP), and four isolates had an insertion or a deletion in their coding regions. No significant difference in biochemical characteristics was observed among ProHR isolates from two different hosts, though mutations in AaHK1 of the cabbage-originated ProHR isolates were distinct from those of the broccoli-originated ProHR isolates.

scholarly journals Tenebenal: a meta-diamide with potential for use as a novel mode of action insecticide for public health

2020 ◽  
Vol 19 (1) ◽  
Author(s):  
Rosemary Susan Lees ◽  
Pauline Ambrose ◽  
Jessica Williams ◽  
John Morgan ◽  
Giorgio Praulins ◽  
...  
Keyword(s):  
Public Health ◽  
Vector Control ◽  
Topical Application ◽  
Mode Of Action ◽  
Application Rate ◽  
Intrinsic Activity ◽  
Cross Resistance ◽  
Laboratory Assessment ◽  
Health Products ◽  
Residual Efficacy

Abstract Background There is an urgent need for insecticides with novel modes of action against mosquito vectors. Broflanilide is a meta-diamide, discovered and named Tenebenal™ by Mitsui Chemicals Agro, Inc., which has been identified as a candidate insecticide for use in public health products. Methods To evaluate its potential for use in public health, Tenebenal™ was screened using an array of methodologies against Anopheles and Aedes strains. Initially it was assessed for intrinsic efficacy by topical application. Tarsal contact bioassays were then conducted to further investigate its efficacy, as well as its potency and speed of action. The potential of the compound for use in indoor residual spray (IRS) applications was investigated by testing the residual efficacy of a prototype IRS formulation on a range of typical house building substrates, and its potential for use in long-lasting insecticidal nets (LLIN) was tested using dipped net samples. Finally, bioassays using well-characterized insecticide-resistant mosquito strains and an in silico screen for mutations in the insecticide’s target site were performed to assess the risk of cross-resistance to Tenebenal™. Results Tenebenal™ was effective as a tarsal contact insecticide against both Aedes and Anopheles mosquitoes, with no apparent cross-resistance caused by mechanisms that have evolved to insecticides currently used in vector control. Topical application showed potent intrinsic activity against a Kisumu reference strain and an insecticide-resistant strain of Anopheles gambiae. Applied to filter paper in a WHO tube bioassay, Tenebenal™ was effective in killing 100% of susceptible and resistant strains of An. gambiae and Aedes aegypti at a concentration of 0.01%. The discriminating concentration of 11.91 µg/bottle shows it to be very potent relative to chemistries previously identified as having potential for vector control. Mortality occurs within 24 h of exposure, 80% of this mortality occurring within the first 10 h, a speed of kill somewhat slower than seen with pyrethroids due to the mode of action. The potential of Tenebenal™ for development in LLIN and IRS products was demonstrated. At least 12 months residual efficacy of a prototype IRS formulation applied at concentrations up to 200 mg of AI/sq m was demonstrated on a range of representative wall substrates, and up to 18 months on more inert substrates. A dipped net with an application rate of around 2 g/sq m Tenebenal™ killed 100% of exposed mosquitoes within a 3-min exposure in a WHO cone test. Conclusions Tenebenal™ is a potent insecticide against adult Aedes and Anopheles mosquitoes, including strains resistant to classes of insecticide currently used in vector control. The compound has shown great potential in laboratory assessment and warrants further investigation into development for the control of pyrethroid-resistant mosquitoes.

Halogenation Enhances the Photosystem II Inhibitory Activity of 4-Hydroxypyridines: Structure-Activity Relationships and Their Mode of Action

1993 ◽  
Vol 48 (3-4) ◽  
pp. 152-158 ◽  
Author(s):  
Tadao Asami ◽  
Masatoshi Baba ◽  
Hiroyuki Koike ◽  
Yorinao Inoue ◽  
Shigeo Yoshida
Keyword(s):  
Photosystem Ii ◽  
Mode Of Action ◽  
Phenyl Ring ◽  
Pyridine Ring ◽  
Functional Group ◽  
Photosynthetic Electron Transport ◽  
Cross Resistance ◽  
Side Chain ◽  
Structural Resemblance ◽  
Structure Activity

Abstract A range of 4-hydroxypyridines were synthesized and their activity as PET inhibitors were investigated with regard to their structural resemblance to plastoquinone in photosynthetic electron transport (PET). The activity of these compounds was markedly enhanced upon modifying their structures: introduction of halogens into both the 3-and 5-positions of the pyridine ring and additional substitution at the α-position of the side chain at 6-position were effective among others in enhancing the activity. Insertion of a phenyl ring into the side chain at 6-position of the pyridine ring also increased the activity. Substituents on the phenyl ring greatly affected the activity: when substituted with an appropriate functional group, the compounds became 10-to 100-fold more active. The mode of action of both halogenated and non-halogenated 4-hydroxypyridines were investigated by means of thermoluminescence measurements and cross resistance examination against atrazine-resistant thylakoids having mutation in D 1 protein. It was inferred that upon halogenation, 4-hydroxypyridines changed their mode of action from plastoquinone-pool inhibitors to phenol-type inhibitors.

Sign in / Sign up

Export Citation Format

Share Document