scholarly journals Lack of an intron in cytochrome b and overexpression of sterol 14α-demethylase indicate a potential risk for QoI and DMI resistance development in Neophysopella spp. on grapes

2021 ◽  
Author(s):  
Ricardo Feliciano Santos ◽  
Lilian Amorim ◽  
Ana K.M. Wood ◽  
Líllian Beatriz Bibiano ◽  
Bart Fraaije
Keyword(s):  
Cytochrome B ◽  
Potential Risk ◽  
Leaf Disc ◽  
Fold Increase ◽  
Resistance Mechanisms ◽  
Resistance Development ◽  
Quinone Outside Inhibitor ◽  
Dmi Fungicides ◽  
The Mean ◽  
Dmi Resistance

Asian grapevine leaf rust, caused by Neophysopella meliosmae-myrianthae and N. tropicalis, is often controlled by quinone outside inhibitor (QoI) and demethylation inhibitor (DMI) fungicides in Brazil. Here, we evaluated the sensitivity of 55 Neophysopella spp. isolates to pyraclostrobin (QoI) and tebuconazole (DMI). To elucidate the resistance mechanisms, we analyzed the sequences of the cytochrome b (CYTB) and cytochrome P450 sterol 14α-demethylase (CYP51) target proteins of QoI and DMI fungicides, respectively. The CYP51 expression levels were also determined in a selection of isolates. In leaf disc assays, the mean 50% effective concentration (EC50) value for pyraclostrobin was around 0.040 µg/ml for both species. CYTB sequences were identical among all 55 isolates, which did not contain an intron immediately after codon 143. No amino acid substitution was identified at codons 129, 137 and 143. The mean EC50 value for tebuconazole was 0.62 µg/ml for N. tropicalis and 0.46 µg/ml for N. meliosmae-myrianthae and no CYP51 sequence variation was identified among isolates of the same species. However, five N. meliosmae-myrianthae isolates grew on leaf discs treated at 10 µg/ml tebuconazole and these were further exposed to tebuconazole selection pressure. Tebuconazole-adapted laboratory isolates of N. meliosmae-myrianthae showed an eight- to 25-fold increase in resistance after four rounds of selection that was not associated with CYP51 target alterations. In comparison with sensitive isolates, CYP51 expression was induced in the presence of tebuconazole in three out of four tebuconazole-adapted isolates tested. These results suggest a potential risk for QoI and DMI resistance development in Neophysopella spp.

scholarly journals Resistance behaviour of Septoria tritici to some fungicides in the territory of the Czech Republic

2012 ◽  
Vol 58 (1) ◽  
pp. 79-84 ◽  
Author(s):  
Ludvik Tvaružek ◽  
P. Horáková ◽  
L. Ji
Keyword(s):  
Czech Republic ◽  
Septoria Tritici ◽  
Resistance Development ◽  
The Czech Republic ◽  
Colony Diameter ◽  
Dmi Fungicides ◽  
The Mean ◽  
Different Parts ◽  
Pathogen Strains

Reduction of colony diameter using two DMI-fungicides and one strobilurine fungicide was evaluated in the <i>Septoria tritici</i> population. In an <i>in vitro</i> assay, 57 strains of <i>S. tritici</i> originating from different parts of the Czech Republic were grown on agar plates containing different concentrations of fungicides. The mean EC<sub>50</sub> values of strains were analysed for flusilazole (Capitain), metconazole (Caramba) and one strobilurine fungicide: azoxystrobin (Amistar). ED 50 values for metconazole were low. There were highly significant correlation in reaction of pathogen strains to metconazole and flusilazole. Some isolates showed significant higher level of resistance to azoxystrobin. The data will be used in a continuing survey of resistance development in the <i>S. tritici</i> population originating from the territory of the Czech Republic.

scholarly journals Tank Mixing Fungicides for Effectiveness Against Eastern Filbert Blight of Hazelnut

Plant Disease ◽  
2018 ◽  
Vol 102 (5) ◽  
pp. 919-924 ◽  
Author(s):  
J. W. Pscheidt ◽  
S. Heckert ◽  
S. A. Cluskey
Keyword(s):  
Corylus Avellana ◽  
Resistance Development ◽  
Qoi Fungicides ◽  
Quinone Outside Inhibitor ◽  
Action Committee ◽  
Anisogramma Anomala ◽  
Dmi Fungicides ◽  
Group 3 ◽  
Eastern Filbert Blight ◽  
Control Tank

Hazelnut (Corylus avellana) production in Oregon primarily occurs on cultivars susceptible to Anisogramma anomala, the causal agent of eastern filbert blight (EFB). Management of EFB involves planting resistant cultivars, removal of cankered limbs, and the application of fungicides. Tank mixes of demethylation-inhibiting (DMI; Fungicide Resistance Action Committee [FRAC] group 3) or quinone outside inhibitor (QoI; FRAC group 11) fungicides with chlorothalonil (FRAC group M5) at full or reduced rates were evaluated for effectiveness against A. anomala. The use of chlorothalonil in a mix with a DMI or QoI fungicide was an effective treatment for EFB even if each component of the mix was at half the labeled rate. Different liquid or dry formulations of chlorothalonil were equally effective in a tank mix for EFB control. The combination of propiconazole (FRAC group 3) tank mixed with trifloxystrobin (FRAC group 11) was not effective, whereas trees treated with propiconazole tank mixed with pyraclostrobin (FRAC group 11) resulted in significantly fewer EFB cankers compared with nontreated trees. When using tank mixes for EFB management, DMI fungicides should remain at full rates while mixing with a half-rate of chlorothalonil. In contrast, QoI fungicides and chlorothalonil could both be used at half-rates and still maintain acceptable EFB control. Tank mixing chlorothalonil with fungicides at risk of resistance development can help maintain consistent EFB control and should help prevent or delay the emergence of fungicide-resistant A. anomala isolates.

scholarly journals Adaptation to Fungicides in Monilinia fructicola Isolates with Different Fungicide Resistance Phenotypes

2008 ◽  
Vol 98 (2) ◽  
pp. 230-238 ◽  
Author(s):  
Chao-Xi Luo ◽  
Guido Schnabel
Keyword(s):  
Fungicide Resistance ◽  
Monilinia Fructicola ◽  
Uv Mutagenesis ◽  
Resistance Development ◽  
Quinone Outside Inhibitor ◽  
Induced Mutants ◽  
Dmi Fungicides ◽  
Selection Medium ◽  
Parental Isolate ◽  
Higher Doses

The ability to develop fungicide resistance was assessed in Monilinia fructicola isolates with different fungicide sensitivity phenotypes by adapting mycelium and conidia to increasing concentrations of selective fungicides and UV mutagenesis. Results showed that adaptation to Quinone outside inhibitor (QoI) fungicide azoxystrobin and sterol demethylation inhibitor (DMI) fungicide propiconazole was more effective in conidial-transfer experiments compared to mycelial-transfer experiments. DMI-resistant (DMI-R) isolates adapted to significantly higher doses of azoxystrobin in both, mycelial- and conidial-transfer experiments compared to benzimidazole-resistant (BZI-R) and sensitive (S) isolates. Adaptation to propiconazole in conidial-transfer experiments was accelerated in BZI-R isolates when a stable, nonlethal dose of 50 μg/ml thiophanate-methyl was added to the selection medium. One of two azoxystrobin-resistant mutants from DMI-R isolates did not show any fitness penalties; the other isolate expired before further tests could be carried out. The viable mutant caused larger lesions on detached peach fruit sprayed with azoxystrobin compared to the parental isolate. The azoxystrobin sensitivity of the viable mutant returned to baseline levels after the mutant was transferred to unamended medium. However, azoxystrobin resistance recovered quicker in the mutant compared to the corresponding parental isolate after renewed subculturing on medium amended with 0.2 and 1 μg/ml azoxystrobin; only the mutant but not the parental isolate was able to adapt to 5 μg/ml azoxystrobin. In UV mutagenesis experiments, the DMI-R isolates produced significantly more mutants compared to S isolates. All of the UV-induced mutants showed stable fungicide resistance with little fitness penalty. This study indicates the potential for QoI fungicide resistance development in M. fructicola in the absence of a mutagen and provides evidence for increased mutability and predisposition to accelerated adaptation to azoxystrobin in M. fructicola isolates resistant to DMI fungicides.

Fungicide Sensitivity Survey of Plasmopara viticola Populations in Georgia Vineyards

2020 ◽  
Vol 21 (4) ◽  
pp. 256-261
Author(s):  
Sarah E. Campbell ◽  
Phillip M. Brannen ◽  
Harald Scherm ◽  
Marin T. Brewer
Keyword(s):  
Downy Mildew ◽  
Acid Amide ◽  
Leaf Disc ◽  
Plasmopara Viticola ◽  
Survey Period ◽  
Resistance Development ◽  
Grapevine Downy Mildew ◽  
Quinone Outside Inhibitor ◽  
History Of ◽  
Qoi Resistance

Grapevine downy mildew, caused by Plasmopara viticola, is among the most damaging diseases of grapes globally and in the viticultural regions of Georgia (U.S.A.). Although management of this disease typically involves fungicide applications, resistance development in P. viticola can render chemical management ineffective. The objective of this study was to survey fungicide sensitivities of P. viticola populations in vineyards across three regions in Georgia. Samples were collected from eight vineyards in 2017 and four in 2018 and tested phenotypically for sensitivity to quinone outside inhibitor (QoI), carboxylic acid amide (CAA), and phenylamide (PA) fungicides using leaf disc bioassays. In addition, DNA was extracted from P. viticola samples collected from 2015 through 2018 in these 12 vineyards and six others for a total of 18 vineyards sampled. All available DNA samples were tested for the presence of the known resistance-causing mutations G143A (QoI) and G1105S (CAA) using polymerase chain reaction (PCR). This study documented widespread occurrence of QoI resistance in P. viticola in Georgia, with 83.0% of isolates collected in 2017 and 2018 testing positive for QoI resistance based on bioassay and 82.9% of isolates collected from 2015 to 2018 testing positive for QoI resistance through PCR testing. In total, 94.4% (17/18) of surveyed vineyards had confirmed QoI resistance by the conclusion of the survey period. No reduced sensitivity to CAA or PA fungicides was identified. Due to widespread QoI resistance, these fungicides should not be relied upon for downy mildew management in Georgia vineyards with a long history of their use.

Necrotising (malignant) otitis externa in the UK: a growing problem. Review of five cases and analysis of national Hospital Episode Statistics trends

2015 ◽  
Vol 129 (6) ◽  
pp. 600-603 ◽  
Author(s):  
G Chawdhary ◽  
N Liow ◽  
J Democratis ◽  
O Whiteside
Keyword(s):  
Otitis Externa ◽  
Severe Infection ◽  
Fold Increase ◽  
Antibiotic Resistant ◽  
Catchment Population ◽  
Malignant Otitis Externa ◽  
The Mean ◽  
The Uk ◽  
High Index Of Suspicion ◽  
Park Hospital

AbstractBackground:Necrotising (malignant) otitis externa is a severe infection causing temporal bone osteomyelitis. Although rare, our experience (reported herein) shows local doubling of cases in 2013. Hospital Episodes Statistics data for England over 14 years also indicate increased incidence nationally. Specific learning points in management are also discussed.Methods:A retrospective review was conducted of patients admitted in 2013 to Wexham Park Hospital, Slough, UK (catchment population, 450 000). In addition, the UK Government Hospital Episodes Statistics data were interrogated.Results:There were five cases of necrotising (malignant) otitis externa in 2013, representing a local doubling on previous years. The mean age of patients was 82 years. All cultures grew Pseudomonas aeruginosa; no isolates were antibiotic resistant. All patients responded to systemic anti-pseudomonals on clinical, biochemical and radiological parameters. Hospital Episodes Statistics data showed a six-fold increase in the number of cases from 1999 (n = 67) to 2013 (n = 421).Conclusion:Our experience suggests increasing necrotising (malignant) otitis externa incidence, and retrospective analysis of Hospital Episodes Statistics data supports this observation. Necrotising (malignant) otitis externa poses challenges in management, as exemplified in our cases, requiring a high index of suspicion and early aggressive treatment to achieve cure.

scholarly journals Development of Resistance in Wild-Type and Hypermutable Pseudomonas aeruginosa Strains Exposed to Clinical Pharmacokinetic Profiles of Meropenem and Ceftazidime Simulated In Vitro

2007 ◽  
Vol 51 (10) ◽  
pp. 3642-3649 ◽  
Author(s):  
Beate Henrichfreise ◽  
Irith Wiegand ◽  
Ingeborg Luhmer-Becker ◽  
Bernd Wiedemann
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Parent Strain ◽  
Resistance Mechanisms ◽  
In Vitro Models ◽  
Wild Type ◽  
Resistance Development ◽  
Development Of Resistance ◽  
Pharmacokinetic Profiles ◽  
Mutant Prevention Concentration

ABSTRACT In this study we investigated the interplay of antibiotic pharmacokinetic profiles and the development of mutation-mediated resistance in wild-type and hypermutable Pseudomonas aeruginosa strains. We used in vitro models simulating profiles of the commonly used therapeutic drugs meropenem and ceftazidime, two agents with high levels of antipseudomonal activity said to have different potentials for stimulating resistance development. During ceftazidime treatment of the wild-type strain (PAO1), fully resistant mutants overproducing AmpC were selected rapidly and they completely replaced wild-type cells in the population. During treatment with meropenem, mutants of PAO1 were not selected as rapidly and showed only intermediate resistance due to the loss of OprD. These mutants also replaced the parent strain in the population. During the treatment of the mutator P. aeruginosa strain with meropenem, the slowly selected mutants did not accumulate several resistance mechanisms but only lost OprD and did not completely replace the parent strain in the population. Our results indicate that the commonly used dosing regimens for meropenem and ceftazidime cannot avoid the selection of mutants of wild-type and hypermutable P. aeruginosa strains. For the treatment outcome, including the prevention of resistance development, it would be beneficial for the antibiotic concentration to remain above the mutant prevention concentration for a longer period of time than it does in present regimens.

Sensitivity of C. fructicola and C. siamense of peach in China to multiple classes of fungicides and characterization of pyraclostrobin-resistant isolates

Plant Disease ◽  
2021 ◽  
Author(s):  
Hafiz Muhammad Usman ◽  
Qin Tan ◽  
Mohammad Mazharul Karim ◽  
Muhammad Adnan ◽  
Weixiao Yin ◽  
...  
Keyword(s):  
High Resistance ◽  
Mycelial Growth ◽  
Management Strategies ◽  
Cross Resistance ◽  
Qoi Fungicides ◽  
Quinone Outside Inhibitor ◽  
Dmi Fungicides ◽  
Colletotrichum Gloeosporioides Species Complex ◽  
Cyt B Gene

Anthracnose, mainly caused by Colletotrichum gloeosporioides species complex including C. fructicola and C. siamense, is a devastating disease of peach. The chemical control has been widely used for years and management failures have increased towards commonly used fungicides. Therefore, screening of sensitivity of Colletotrichum spp. to fungicides with different modes of action is needed to make proper management strategies for peach anthracnose. In this study, sensitivity of 80 isolates of C. fructicola and C. siamense was screened for pyraclostrobin, procymidone, prochloraz and fludioxonil based on mycelial growth inhibition at discriminatory doses. Results showed that C. fructicola and C. siamense isolates were highly resistant to procymidone and fludioxonil with 100% resistance frequencies to both fungicides, but sensitive to prochloraz, i.e., no resistant isolates were found. For pyraclostrobin, 74% of C. fructicola isolates showed high resistance and 26 % were low resistant, all of the C. siamense isolates were low resistant. No positive cross-resistance was observed between pyraclostrobin and azoxystrobin, even they are members of the same quinone outside inhibitor (QoI) fungicide group, and between pyraclostrobin and non-QoIs. Resistant isolates to QoI fungicides were evaluated for the fitness penalty. Results showed that no significant differences except for mycelial growth rates were detected between highly resistant and low-resistant isolates of C. fructicola. Molecular characterization of Cyt b gene revealed that the G143A point mutation was the determinant of the high resistance in C. fructicola. This study demonstrated the current resistance status of C. fructicola and C. siamense to different fungicides and their future perspectives. Demethylation inhibitor (DMI) fungicides are the best option among different chemicals to control peach anthracnose in China.

scholarly journals Characterization of Quinone Outside Inhibitor Fungicide Resistance in Cercospora sojina and Development of Diagnostic Tools for its Identification

Plant Disease ◽  
2015 ◽  
Vol 99 (4) ◽  
pp. 544-550 ◽  
Author(s):  
F. Zeng ◽  
E. Arnao ◽  
G. Zhang ◽  
G. Olaya ◽  
J. Wullschleger ◽  
...  
Keyword(s):  
Cytochrome B ◽  
Leaf Spot ◽  
Fungicide Resistance ◽  
Cytochrome B Gene ◽  
Diagnostic Tools ◽  
Polymerase Chain Reaction Primer ◽  
Cercospora Sojina ◽  
Qoi Fungicides ◽  
Quinone Outside Inhibitor ◽  
Frogeye Leaf Spot

Frogeye leaf spot of soybean, caused by the fungus Cercospora sojina, reduces soybean yields in most of the top-producing countries around the world. Control strategies for frogeye leaf spot can rely heavily on quinone outside inhibitor (QoI) fungicides. In 2010, QoI fungicide-resistant C. sojina isolates were identified in Tennessee for the first time. As the target of QoI fungicides, the cytochrome b gene present in fungal mitochondria has played a key role in the development of resistance to this fungicide class. The cytochrome b genes from three QoI-sensitive and three QoI-resistant C. sojina isolates were cloned and sequenced. The complete coding sequence of the cytochrome b gene was identified and found to encode 396 amino acids. The QoI-resistant C. sojina isolates contained the G143A mutation in the cytochrome b gene, a guanidine to cytosine transversion at the second position in codon 143 that causes an amino acid substitution of alanine for glycine. C. sojina-specific polymerase chain reaction primer sets and TaqMan probes were developed to efficiently discriminate QoI-resistant and -sensitive isolates. The molecular basis of QoI fungicide resistance in field isolates of C. sojina was identified as the G143A mutation, and specific molecular approaches were developed to discriminate and to track QoI-resistant and -sensitive isolates of C. sojina.

scholarly journals Iron absorption from a cereal-based meal containing cane sugar fortified with ascorbic acid

1977 ◽  
Vol 38 (2) ◽  
pp. 261-269 ◽  
Author(s):  
D. Derman ◽  
M. Sayers ◽  
S. R. Lynch ◽  
R. W. Charlton ◽  
T. H. Bothwell ◽  
...  
Keyword(s):  
Ascorbic Acid ◽  
Ferric Hydroxide ◽  
Fold Increase ◽  
Inhibitory Effect ◽  
Cane Sugar ◽  
Iron Nutrition ◽  
Indian Women ◽  
Mean Values ◽  
Maize Meal ◽  
The Mean

1. The feasibility of improving iron nutrition by fortifying cane sugar with ascorbic acid was studied.2. The absorption of Fe added to maize-weal porridge was measured in 116 volunteer multiparous Indian women using the radio-Fe erythrocyte utilization method. The meals were fed with and without tea or coffee and with and without varying amounts of ascorbic acid.3. The mean absorption of Fe from maize-meal porridge was very low (3.8 %), being even further reduced (2.1 %) when tea was drunk with the meal.4. The addition of 50 or 100 mg ascorbic acid to maize-meal porridge caused approximately a 10-fold increase in Fe absorption. The increase was much less when tea was present, being 2-fold and 5-fold with 50 and 100 mg ascorbic acid respectively. The inhibitory effect of tea on Fe absorption could, however, be overcome by giving larger doses of ascorbic acid (250 and 500 mg).5. When contaminating Fe (2.5 mg) in the form of labelled rust (Fe2O3) or ferric hydroxide was added to maize-meal porridge it was poorly absorbed (mean values were 0.01 % and 1.5 % respectively). The addition of 100 mg ascorbic acid increased the mean Fe absorption rates to 0.5 % and 6.7 % with Fe2O3 and Fe(OH)3 respectively. Fe(OH)3 was found to be absorbed about half as well as the intrinsic Fe present in maize-meal porridge.6. It is concluded that ascorbic acid is capable of improving Fe absorption from a cereal source. It can partially overcome the inhibitory effect of tea and might be expected to facilitate the absorption of at least some forms of Fe that may contaminate food.

scholarly journals Comparative Study of the Effect of Solvents on the Efficacy of Neonicotinoid Insecticides Against Malaria Vector Populations Across Africa

2022 ◽  
Author(s):  
Magellan Tchouakui ◽  
Tatiane Assatse ◽  
Leon M. J. Mugenzi ◽  
Benjamin D. Menze ◽  
Daniel Nguiffo-Nguete ◽  
...  
Keyword(s):  
Democratic Republic Of Congo ◽  
Natural Populations ◽  
Resistance Mechanisms ◽  
Lower Mortality ◽  
Malaria Vectors ◽  
Cross Resistance ◽  
Metabolic Resistance ◽  
Resistance Development ◽  
Development Of Resistance ◽  
Bottle Test

Abstract Background New insecticides with a novel mode of action such as neonicotinoids have recently been recommended for public health by WHO. Resistance monitoring of such novel insecticides requires a robust protocol to monitor the development of resistance in natural populations. In this study, we comparatively used three different solvents to assess the susceptibility of malaria vectors to neonicotinoids across Africa.MethodsMosquitoes were collected from May to July 2021 from three agricultural settings in Cameroon (Njombe-Penja, Nkolondom, and Mangoum), the Democratic Republic of Congo (Ndjili-Brasserie), Ghana (Obuasi), and Uganda (Mayuge). Using the CDC bottle test, we compared the effect of three different solvents (ethanol, acetone, MERO) on the efficacy of neonicotinoids against Anopheles gambiae s.l. In addition, TaqMan assays were used to genotype key pyrethroid-resistant markers in An. gambiae and to evaluate potential cross-resistance between pyrethroids and clothianidin.ResultsLower mortality were observed when using absolute ethanol or acetone alone as solvent (11.4- 51.9% mortality in Nkolondom, 31.7- 48.2% in Mangoum, 34.6- 56.1% in Mayµge, 39.4- 45.6% in Obuasi, 83.7- 89.3% in Congo and 71.05- 95.9% in Njombe pendja) compared to acetone + MERO for which 100% mortality were observed for all the populations. Synergist assays (PBO, DEM and DEF) revealed a significant increase of mortality suggesting that metabolic resistance mechanisms are contributing to the reduced susceptibility. A negative association was observed between the L1014F-kdr mutation and clothianidin resistance with a greater frequency of homozygote resistant mosquitoes among the dead than among survivors (OR=0.5; P=0.02). However, the I114T-GSTe2 was in contrast significantly associated with a greater ability to survive clothianidin with a higher frequency of homozygote resistant among survivors than other genotypes (OR=2.10; P=0.013). ConclusionsThis study revealed a contrasted susceptibility pattern depending on the solvents with ethanol/acetone resulting to lower mortality, thus possibly overestimating resistance, whereas the MERO consistently showed a greater efficacy of neonicotinoids but it could prevent to detect early resistance development. Therefore, we recommend monitoring the susceptibility using both acetone alone and acetone+MERO (8-10µg/ml for clothianidin) to capture the accurate resistance profile of the mosquito populations.

Sign in / Sign up

Export Citation Format

Share Document