thiophanate and benzimidazole

Multiple resistance to albendazole, thiophanate, levamisole and orally administered invermectin was detected in an isolate of Haemonchus contortus in sheep on a farm where benzimidazole resistance had already been identified. Following a faecal egg count reduction test, this was confirmed by both critical and controlled anthelmintic tests. Different groups of sheep infected naturally or given an experimental infection with the benzimidazole-resistant isolate were treated with the recommended doses of various anthelmintics. Compared to the control group, the percentage reductions in the faecal egg counts of sheep treated with albendazole, thiophanate, levamisole and ivermectin varied between 38.2% and 79.1% and the residual worm counts between 27.3% and 57.5%. The results indicate the presence of multiple anthelmintic resistance in this isolate of H. contortus. Sheep treated with closantel showed 100% reductions in faecal egg and worm counts, indicating that this drug was very effective against the population of H. contortus on the farm.

Topics: Administration, Oral; Albendazole; Animals; Anthelmintics; Benzimidazoles; Dose-Response Relationship, Drug; Drug Resistance, Multiple; Feces; Haemonchiasis; Haemonchus; Ivermectin; Kenya; Levamisole; Parasite Egg Count; Salicylanilides; Sheep; Sheep Diseases; Thiophanate

The benzimidazole fungicide thiophanate-methyl is commonly used for the control of brown rot of stone fruits. Low and high levels of resistance to this fungicide have been found in field isolates of the causal pathogen Monilinia fructicola.. The minor groove binding (MGB) TaqMan probes specific for alleles E198A and H6Y conferring the high and low levels of resistance in the β-tubulin gene of M. fructicola were designed. A duplex real-time PCR assay based on these probes was developed for simultaneous quantification of both mutations in a pathogen population. The specificity tests for the primers and probes were conducted using different fungal species of stone and pome fruit pathogens. Similar results were obtained between the duplex real-time (TaqMan) PCR assay and the conventional method to quantify the frequencies of alleles E198A and H6Y of eight samples from different peach orchards.. The MGB TaqMan probe based duplex real-time PCR provides a useful tool for simultaneous quantification of both alleles, E198A and H6Y, conferring high and low resistance, and has a potential in monitoring the benzimidazole-resistance in M. fructicola populations in stone and pome fruit orchards.

Topics: Alleles; Ascomycota; Benzimidazoles; DNA Primers; Drug Resistance, Fungal; Fungicides, Industrial; Gene Frequency; Real-Time Polymerase Chain Reaction; Taq Polymerase; Thiophanate; Tubulin

The efficacy of benzimidazole fungicides is often limited by resistance, and this is the case with the use of carbendazim for controlling Fusarium head blight caused by Gibberella zeae (Schwein.) Petch (anamorph Fusarium graminearum). Recent studies have shown that carbendazim resistance in field strains of G. zeae is associated with mutations in the β(2)-tubulin gene. The aims of the present study were to validate this mechanism and research the binding sites of carbendazim on β(2)-tubulin.. This work used site-directed mutagenesis followed by gene replacement to change the β(2)-tubulin gene of a carbendazim-sensitive field strain of G. zeae at residues 50, 167, 198 or 200. The transformants were confirmed and tested for their sensitivity to carbendazim. All the mutants were resistant to carbendazim, but the level of resistance differed depending on the mutation. Biological characteristics did not differ between the field strain and the site-directed mutants. A three-dimensional model of β(2)-tubulin was constructed, and the possible carbendazim binding site was analysed.. Mutations at codons 50, 167, 198 and 200 of G. zeae β(2)tub could cause resistance to carbendazim, and these codons may form a binding pocket.

Topics: Benzimidazoles; Binding Sites; Drug Resistance, Fungal; Fungal Proteins; Fungicides, Industrial; Gibberella; Mutagenesis, Site-Directed; Mutation; Protein Binding; Tubulin

The benzimidazole fungicide thiophanate-methyl is commonly applied to control leaf mould of tomato caused by Cladosporium fulvum in China. In this study, 32 isolates of C. fulvum were examined for their sensitivities to thiophanate-methyl, and two benzimidazole-resistant (BenR) phenotypes BenR1 and BenR2 were identified. The BenR1 isolates were resistant to thiophanate-methyl, but were more sensitive to the phenylcarbamate fungicide diethofencarb than the wild-type isolates. The BenR2 isolates resistant to thiophanate-methyl were insensitive to diethofencarb. All tested isolates were sensitive to the dicarboximide fungicide iprodione. The complete beta-tubulin gene was isolated from this fungus to study its potential role in benzimidazole resistance. Analysis of the DNA sequence of the beta-tubulin gene showed that the BenR1 isolates had a point mutation at codon 198, causing a substitution of glutamic acid to alanine. In the BenR2 isolates, a point mutation at codon 200 causing a substitution of phenylalanine to tyrosine was detected. Based on these point mutations, a multiplex allele-specific PCR method was developed successfully for the first time to detect two point mutations at the beta-tubulin gene simultaneously in single PCR amplifications.

Topics: Aminoimidazole Carboxamide; Benzimidazoles; Cladosporium; Codon; Drug Resistance, Fungal; Fungicides, Industrial; Hydantoins; Phenylcarbamates; Point Mutation; Polymerase Chain Reaction; Thiophanate; Tubulin