scholarly journals Resistance mechanisms and fitness of pyraclostrobin-resistant isolates of Lasiodiplodia theobromae from mango orchards

PLoS ONE ◽  
2021 ◽  
Vol 16 (6) ◽  
pp. e0253659
Author(s):  
Rui He ◽  
Ye Yang ◽  
Zhizhong Hu ◽  
Ru Xue ◽  
Yajuan Hu
Keyword(s):  
Temperature Sensitivity ◽  
Mycelial Growth ◽  
Rapid Development ◽  
Resistance Mechanisms ◽  
Stress Sensitivity ◽  
Cell Membrane Permeability ◽  
Postharvest Disease ◽  
Metabolic Resistance ◽  
Lasiodiplodia Theobromae ◽  
Relative Conductivity

Background Stem-end rot, caused by Lasiodiplodia theobromae (Pat.) Griffon & Maubl is a serious postharvest disease in mango. In China, a high prevalence of the QoI fungicides resistance has been reported in the last decade. The study aimed to discuss factors determining rapid development of pyraclostrobin-resistance and its resistance mechanisms. Methods To determine the resistance stability and fitness of pyraclostrobin resistance in L. theobromae, three phenotypes of pyraclostrobin resistance were compared and analyzed for the EC50 values, mycelial growth, virulence and temperature sensitivity and osmotic stress sensitivity. The relative conductivity and enzyme activities of different phenotypes were compared under fungicide stress to explore possible biochemical mechanisms of pyraclostrobin resistance in L. theobromae. The Cytb gene sequences of different phenotypes were analysed. Results All isolates retained their original resistance phenotypes during the 10 subcultures on a fungicide-free PDA, factor of sensitivity change (FSC) was approximately equal to 1. The resistance-pyraclostrobin of the field isolates should be relatively stable. Two pyraclostrobin-resistant phenotypes shared similar mycelial growth, virulence and temperature sensitivity with pyraclostrobin-sensitive phenotype. After treated by pyraclostrobin, the relative conductivity of the sensitive phenotype was significantly increased. The time of Pyr-R and Pyr-HR reached the most conductivity was about 8–10 times than that of Pyr-S, the time for the maximum value appearance showed significant differences between sensitive and resistant phenotypes. The activities of Glutathione S-transferase (GST), catalase (CAT) and peroxidase (POD) of Pyr-HR were 1.78, 5.45 and 1.65 times respectively, significantly higher than that of Pyr-S after treated by 200 mg/l pyraclostrobin. Conclusion The results showed that the pyraclostrobin-resistant phenotypes displayed high fitness and high-risk. The nucleotide sequences were identical among all pyraclostrobin-resistant and -sensitive isolates. The pyraclostrobin resistance was not attributable to Cytb gene alterations, there may be some of other resistance mechanisms. Differential response of enzyme activity and cell membrane permeability were observed in resistant- and sensitive-isolates suggesting a mechanism of metabolic resistance.

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.

scholarly journals Suppression of Stem-End Rot on Avocado Fruit Using Trichoderma spp. in the Central Highlands of Kenya

2021 ◽  
Vol 2021 ◽  
pp. 1-6
Author(s):  
E. K. Wanjiku ◽  
J. W. Waceke ◽  
J. N. Mbaka
Keyword(s):  
Growth Inhibition ◽  
Fungal Pathogen ◽  
Mycelial Growth ◽  
Culture Technique ◽  
Global Market ◽  
Dual Culture ◽  
Postharvest Diseases ◽  
Trichoderma Spp ◽  
Lasiodiplodia Theobromae

Demand for organic avocado fruits, together with stringent food safety standards in the global market, has made producers to use alternative, safe, and consumer-friendly strategies of controlling the postharvest fungal disease of avocado fruits. This study assessed the in vitro efficacy of Trichoderma spp. (T. atroviride, T. virens, T. asperellum, and T. harzianum) against isolated avocado stem-end rot (SER) fungal pathogens (Lasiodiplodia theobromae, Neofusicoccum parvum, Nectria pseudotrichia, and Fusarium solani) using a dual culture technique. The Trichoderma spp. were also evaluated singly on postharvest “Hass” avocado fruits. Spore suspension at 5 × 104 conidial/ml of the Trichoderma spp. was applied on the avocado fruits at three time points, twenty-four hours before the fungal pathogen (preinoculation), at the same time as the fungal pathogen (concurrent inoculation), and 24 hours after the fungal pathogen (postinoculation). In the in vitro study, T. atroviride showed the highest mycelial growth inhibition against N. parvum (48%), N. pseudotrichia (55%), and F. solani (32.95%), while T. harzianum had the highest mycelial growth inhibition against L. theobromae. Trichoderma asperellum was the least effective in inhibiting the mycelial growth of all the pathogens. Similarly, T. virens showed the highest mycelial growth inhibition against N. pseudotrichia at 45% inhibition. On postharvest “Hass” fruits, T. atroviride showed the highest efficacy against N. parvum, N. pseudotrichia, and F. solani in all the applications. Trichoderma virens and T. harzianum were most effective against all the pathogens during postinoculation, while Lasiodiplodia theobromae was best controlled by T. virens, T. harzianum, and T. asperellum during postinoculation. Both T. atroviride and T. harzianum present a potential alternative to synthetic fungicides against postharvest diseases of avocado fruits, and further tests under field conditions to be done to validate their efficacy. The possibility of using Trichoderma spp. in the management of SER on avocado fruits at a commercial level should also be explored.

scholarly journals Investigation of the influence of a glutathione S-transferase metabolic resistance to pyrethroids/DDT on mating competitiveness in males of the African malaria vector, Anopheles funestus

2019 ◽  
Vol 4 ◽  
pp. 13 ◽  
Author(s):  
Magellan Tchouakui ◽  
Billy Tene Fossog ◽  
Brigitte Vanessa Ngannang ◽  
Doumani Djonabaye ◽  
Williams Tchapga ◽  
...  
Keyword(s):  
Natural Populations ◽  
Anopheles Funestus ◽  
Resistance Mechanisms ◽  
Malaria Vectors ◽  
Glutathione S Transferase ◽  
Metabolic Resistance ◽  
Mating Competitiveness ◽  
Metabolic Marker ◽  
Susceptible Allele ◽  
Permanet 3.0

Background: Metabolic resistance is a serious challenge to current insecticide-based interventions. The extent to which it affects natural populations of mosquitoes including their reproduction ability remains uncharacterised. Here, we investigated the potential impact of the glutathione S-transferase L119F-GSTe2 resistance on the mating competitiveness of male Anopheles funestus, in Cameroon. Methods: Swarms and indoor resting collections took place in March, 2018 in Tibati, Cameroon. WHO tube and cone assays were performed on F1 mosquitoes from indoor collected females to assess the susceptibility profile of malaria vectors. Mosquitoes mated and unmated males collected in the swarms were genotyped for the L119F metabolic marker to assess its association with mating male competitiveness. Results: Susceptibility and synergist assays, showed that this population was multiple resistant to pyrethroids, DDT and carbamates, likely driven by metabolic resistance mechanisms. Cone assays revealed a reduced efficacy of standard pyrethroid-nets (Olyset and PermaNet 2.0) with low mortality (<25%) whereas synergist PBO-Nets (Olyset Plus and PermaNet 3.0) retained greater efficacy with higher mortality (>80%). The L119F-GSTe2 mutation, conferring pyrethroid/DDT resistance, was detected in this An. funestus population at a frequency of 28.8%. In addition, a total of 15 mating swarms were identified and 21 An. funestus couples were isolated from those swarms.  A comparative genotyping of the L119F-GSTe2 mutation between mated and unmated males revealed that heterozygote males 119L/F-RS were less able to mate than homozygote susceptible (OR=7.2, P<0.0001). Surprisingly, heterozygote mosquitoes were also less able to mate than homozygote resistant (OR=4.2, P=0.010) suggesting the presence of a heterozygote disadvantage effect. Overall, mosquitoes bearing the L119-S susceptible allele were significantly more able to mate than those with 119F-R resistant allele (OR=2.1, P=0.03). Conclusion: This study provides preliminary evidences that metabolic resistance potentially exerts a fitness cost on mating competiveness in resistant mosquitoes.

scholarly journals Cytological and Gene Profile Expression Analysis Reveals Modification in Metabolic Pathways and Catalytic Activities Induce Resistance in Botrytis cinerea Against Iprodione Isolated From Tomato

2020 ◽  
Vol 21 (14) ◽  
pp. 4865
Author(s):  
Ambreen Maqsood ◽  
Chaorong Wu ◽  
Sunny Ahmar ◽  
Haiyan Wu
Keyword(s):  
Enzymatic Activity ◽  
Rna Sequencing ◽  
Aspartic Acid ◽  
Mycelial Growth ◽  
Plant Pathogens ◽  
Fruits And Vegetables ◽  
Transcriptomic Analysis ◽  
Cell Membrane Permeability ◽  
Wild Type ◽  
Tomato Field

Grey mold is one of the most serious and catastrophic diseases, causing significant yield losses in fruits and vegetables worldwide. Iprodione is a broad spectrum agrochemical used as a foliar application as well as a seed protectant against many fungal and nematode diseases of fruits and vegetables from the last thirty years. The extensive use of agrochemicals produces resistance in plant pathogens and is the most devastating issue in food and agriculture. However, the molecular mechanism (whole transcriptomic analysis) of a resistant mutant of B. cinerea against iprodione is still unknown. In the present study, mycelial growth, sporulation, virulence, osmotic potential, cell membrane permeability, enzymatic activity, and whole transcriptomic analysis of UV (ultraviolet) mutagenic mutant and its wild type were performed to compare the fitness. The EC50 (half maximal effective concentration that inhibits the growth of mycelium) value of iprodione for 112 isolates of B. cinerea ranged from 0.07 to 0.87 µg/mL with an average (0.47 µg/mL) collected from tomato field of Guangxi Province China. Results also revealed that, among iprodione sensitive strains, only B67 strain induced two mutants, M0 and M1 after UV application. The EC50 of these induced mutants were 1025.74 μg/mL and 674.48 μg/mL, respectively, as compared to its wild type 1.12 μg/mL. Furthermore, mutant M0 showed higher mycelial growth sclerotia formation, virulence, and enzymatic activity than wild type W0 and M1 on potato dextrose agar (PDA) medium. The bctubA gene in the mutant M0 replaced TTC and GAT codon at position 593 and 599 by TTA and GAA, resulting in replacement of phenyl alanine into leucine (transversion C/A) and aspartic acid into glutamic acid (transversion T/C) respectively. In contrast, in bctubB gene, GAT codon at position 646 is replaced by AAT and aspartic acid converted into asparagine (transition G/A). RNA sequencing of the mutant and its wild type was performed without (M0, W0) and with iprodione treatment (M-ipro, W-ipro). The differential gene expression (DEG) identified 720 unigenes in mutant M-ipro than W-ipro after iprodione treatment (FDR ≤ 0.05 and log2FC ≥ 1). Seven DEGs were randomly selected for quantitative real time polymerase chain reaction to validate the RNA sequencing genes expression (log fold 2 value). The gene ontology (GO) enrichment and Kyoto encyclopedia genes and genomes (KEGG) pathway functional analyses indicated that DEG’s mainly associated with lysophopholipase, carbohydrate metabolism, amino acid metabolism, catalytic activity, multifunctional genes (MFO), glutathione-S transferase (GST), drug sensitivity, and cytochrome P450 related genes are upregulated in mutant type (M0, M-ipro) as compared to its wild type (W0, W-ipro), may be related to induce resistant in mutants of B. cinerea against iprodione.

scholarly journals Evaluating insecticide resistance across African districts to aid malaria control decisions

2020 ◽  
Vol 117 (36) ◽  
pp. 22042-22050 ◽  
Author(s):  
Catherine L. Moyes ◽  
Duncan K. Athinya ◽  
Tara Seethaler ◽  
Katherine E. Battle ◽  
Marianne Sinka ◽  
...  
Keyword(s):  
Cytochrome P450 ◽  
Pyrethroid Resistance ◽  
Resistance Mechanisms ◽  
World Health ◽  
Malaria Vector Control ◽  
Ensemble Model ◽  
Metabolic Resistance ◽  
The World ◽  
Susceptibility Tests ◽  
Health Organization

Malaria vector control may be compromised by resistance to insecticides in vector populations. Actions to mitigate against resistance rely on surveillance using standard susceptibility tests, but there are large gaps in the monitoring data across Africa. Using a published geostatistical ensemble model, we have generated maps that bridge these gaps and consider the likelihood that resistance exceeds recommended thresholds. Our results show that this model provides more accurate next-year predictions than two simpler approaches. We have used the model to generate district-level maps for the probability that pyrethroid resistance inAnopheles gambiaes.l. exceeds the World Health Organization thresholds for susceptibility and confirmed resistance. In addition, we have mapped the three criteria for the deployment of piperonyl butoxide-treated nets that mitigate against the effects of metabolic resistance to pyrethroids. This includes a critical review of the evidence for presence of cytochrome P450-mediated metabolic resistance mechanisms across Africa. The maps for pyrethroid resistance are available on the IR Mapper website, where they can be viewed alongside the latest survey data.

Fungicidal Actions and Resistance Mechanisms of Prochloraz to Penicillium digitatum

Plant Disease ◽  
2020 ◽  
pp. PDIS-05-20-1128
Author(s):  
Yuchao Zhang ◽  
Bao Zhang ◽  
Chaoxi Luo ◽  
Yanping Fu ◽  
Fuxing Zhu
Keyword(s):  
Cell Membrane ◽  
Target Genes ◽  
Membrane Integrity ◽  
Point Mutations ◽  
Resistance Mechanisms ◽  
Penicillium Digitatum ◽  
Cell Membrane Permeability ◽  
Baseline Sensitivity ◽  
Cell Membrane Integrity ◽  
Citrus Groves

The demethylation inhibitor (DMI) fungicide prochloraz has been widely used in China to control citrus green mold, which is caused by Penicillium digitatum. The 50% effective concentration (EC50) values of prochloraz for 129 isolates of P. digitatum collected in 2017 from citrus groves of four provinces of China ranged from 0.0032 to 0.4582 mg/liter. Analysis of the distribution of natural logarithms of EC50 values indicated that 111 isolates with EC50 values lower than 0.05 mg/liter could be considered sensitive to prochloraz. Relative baseline sensitivity was established based on the 111 sensitive isolates, and the mean EC50 value was 0.0090 ± 0.0054 mg/liter (SD). Prochloraz at 60, 100, and 140 mg/liter provided preventive efficacies of 67.8, 93.0, and 96.4%, respectively. Prochloraz at 0.005 and 0.01 mg/liter disrupted cell membrane integrity of conidia but reduced cell membrane permeability of mycelia. Prochloraz at 0.01 mg/liter reduced ergosterol content in mycelia by 41.8%. Two prochloraz-resistant isolates with EC50 values of 3.97 and 5.68 mg/liter were attained by consecutive subculturing on prochloraz-amended PDA. Studies on the expression levels of three potential target genes, CYP51A, CYP51B, and CYP51C, demonstrated that whether in the absence or presence of prochloraz, only CYP51B in the resistant isolates was overexpressed at least 10-fold higher than that of the sensitive ones. Sequencing of the three genes showed that only CYP51B in the resistant isolates had a 199-bp insertion in the promoter region. In addition, only CYP51B displayed point mutations of G405S, G389C, and Y390S in the coding regions in the resistant isolates. These results were important for understanding the resistance mechanisms of P. digitatum to prochloraz.

Metabolic resistance mechanisms of the housefly (Musca domestica) resistant to pyraclofos

2006 ◽  
Vol 85 (2) ◽  
pp. 76-83 ◽  
Author(s):  
Si-Woo Lee ◽  
Kazunari Ohta ◽  
Shigeki Tashiro ◽  
Toshio Shono
Keyword(s):  
Musca Domestica ◽  
Resistance Mechanisms ◽  
Metabolic Resistance

scholarly journals Widespread Pyrethroid and DDT Resistance in the Major Malaria Vector Anopheles funestus in East Africa Is Driven by Metabolic Resistance Mechanisms

PLoS ONE ◽  
2014 ◽  
Vol 9 (10) ◽  
pp. e110058 ◽  
Author(s):  
Charles Mulamba ◽  
Jacob M. Riveron ◽  
Sulaiman S. Ibrahim ◽  
Helen Irving ◽  
Kayla G. Barnes ◽  
...  
Keyword(s):  
East Africa ◽  
Malaria Vector ◽  
Anopheles Funestus ◽  
Resistance Mechanisms ◽  
Metabolic Resistance ◽  
Ddt Resistance ◽  
Major Malaria Vector

scholarly journals Hormetic response and transcriptome profiling reveal the mechanism underlying metabolic and cuticular resistance to host-specific terpenoid defences in an emerging insect pest, Pagiophloeus tsushimanus (Coleoptera: Curculionidae)

2021 ◽  
Author(s):  
Shouyin Li ◽  
Hui Li ◽  
Jingting Wang ◽  
Cong Chen ◽  
Dejun Hao
Keyword(s):  
Control Strategies ◽  
Insect Pest ◽  
Larval Growth ◽  
Transcriptome Profiling ◽  
Resistance Mechanisms ◽  
Plant Interactions ◽  
Transport Pathway ◽  
Metabolic Resistance ◽  
Hormetic Response ◽  
Cuticular Resistance

Abstract The resistance mechanisms evolved by insects to overcome host-plant allelochemicals are a key consideration in pest management. Camphor oil (EO) and its main component (i.e., D-camphor) form a specific terpenoid-defensive system in camphor trees, Cinnamomum camphora. However, an emerging insect pest, Pagiophloeus tsushimanus, has recently caused serious damage to this intractable plant species and is largely elusive. Here, we used feeding bioassays and RNA-seq to investigate the mechanism underlying the resistance of the beetle to host-specific terpenoid defences. First, a hormetic response in both larval weight and developmental time, which is a highly generalized dose-response phenomenon in toxicology but occurs infrequently in the context of insect-plant interactions, was observed in terpenoid-feeding individuals. Then, comparative transcriptome analysis between terpenoid-feeding and control groups indicated that both CYP450-mediated metabolic resistance and CP-mediated cuticular resistance were jointly employed to cope with terpenoid-induced stress. In addition, a small portion of genes involved in the glucose transport pathway were upregulated at the low D-camphor dose, suggesting that an extra intake of glucose used for larval growth may contribute to a hormetic response. These findings suggested that the dual terpenoid resistance mechanisms in this specialist are an essential precondition for the hormetic response in larval growth, ultimately contributing to the widespread successful colonization of host camphor trees. Overall, our study will open new avenues for understanding insect-plant coevolutionary adaptation and developing durable pest control strategies.

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