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PubMed1991

Genotoxicity of the fungicide dichlofluanid in seven assays.

Seven different endpoints for detection of genotoxicity have been used to demonstrate the DNA-altering properties of Dichlofluanid, a fungicide commonly used in viticulture pest control. Each endpoint (DNA synthesis inhibition test, alkaline viscosimetry, umu-test, alkaline filter elution, FADU-test, 32P-postlabeling, and electron microscopy) shows clear evidence of genotoxicity. These data indicate that application of the fungicide dichlofluanid may be mutagenic and/or carcinogenic for exposed humans.

Aniline Compounds↗
PubMed2006

Comparative enantioseparation of seven triazole fungicides on (S,S)-Whelk O1 and four different cellulose derivative columns.

The comparative enantioseparation of seven chiral triazole fungicides on a Pirkle type (S,S)-Whelk O1 chiral column and four different cellulose derivative columns, namely cellulose tribenzoate (CTB), cellulose tris(4-methylbenzoate) (CTMB), cellulose triphenylcarbamate (CTPC), and cellulose tris(3,5-dimethylphenyl carbamate) (CDMPC), in normal phase mode is described. The seven triazole fungicides investigated were tebuconazole, hexaconazole, myclobutanil, diniconazole, uniconazole, paclobutrazol, and triadimenol. The chiral separation of each solute was investigated with ethanol, n-propanol, iso-propanol, and n-butanol, respectively, as polar modifier in the hexane mobile phase. The results revealed that (S,S)-Whelk O1 was less than universal and only hexaconazole and triadimenol underwent enantioseparation. Among the self-prepared cellulose derivative columns used, the enantiomeric resolution capacities for the studied analytes generally decreased in the order CDMPC > CTPC > CTMB > CTB. The best enantioseparation of the analytes was mostly obtained on CDMPC and none of them were enantioseparated on CTB. The chiral recognition mechanisms between the analytes and the chiral selectors are discussed.

Cellulose↗
PubMed2006

Enhancement of fungicidal and insecticidal activity by reductive alkylation of chitosan.

A series of N-alkyl chitosan (NAC) derivatives were synthesized using a reductive alkylation reaction to examine their fungicidal and insecticidal activity. The chemical structures were characterized by IR and (1)H NMR spectroscopy, and the degree of substitution (DS) ranged from 0.02 to 0.37. Their fungicidal activity was evaluated against the grey mould Botrytis cinerea Pers ex Fr (Leotiales: Sclerotiniaceae) and the rice leaf blast pathogen Pyricularia grisea Sacc [Teleomorph: Magnaporthe grisea (Hebert) Barr] by a radial growth bioassay. It was of interest that most of the NAC derivatives were more active against both fungi than chitosan itself. The most active derivative was N-(2,2-diphenylethyl)chitosan with EC50 values of 0.031 and 0.23 g L(-1) against B. cinerea and P. grisea respectively. In addition, some derivatives, at higher concentrations up to 1.0 g L(-1), inhibited the mycelial growth and spore formation of P. grisea. Bioassays against larvae of the cotton leafworm, Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae) with the NAC derivatives at a rate of 5.0 g kg(-1) in artificial diet demonstrated that N-(3-phenylbutyl)chitosan was the most active compound. In addition, N-propylchitosan, N-undecanylchitosan and N-(3-phenylpropyl)chitosan derivatives strongly inhibited larval weight gain in S. littoralis, with respective reductions of 76, 66 and 65% after 4 days of feeding on treated diet.

Alkylation↗
PubMed2001

Fungicidal activity of beta-thujaplicin analogues.

The fungicidal activity of analogues of beta-thujaplicin, a natural product responsible for the durability of heartwood of several cupressaceous trees, was investigated in vitro on the growth of different white and brown rot fungi involved in wood biodegradation, Coriolus versicolor, Phanerochaete chrysosporium, Poria placenta and Gloephyllum trabeum. The study shows that 2-hydroxycyclohepta-2,4,6-trienone (tropolone), easily prepared according to a literature procedure, possesses interesting fungicidal activity when compared to beta-thujaplicin, azaconazole, tebuconazole and copper oxine, which suggests this compound should be examined further as a potential biocide for wood preservation.

Anti-Infective Agents↗
PubMed2002

Mechanisms influencing the evolution of resistance to Qo inhibitor fungicides.

Fungicides inhibiting the mitochondrial respiration of plant pathogens by binding to the cytochrome bc1 enzyme complex (complex III) at the Qo site (Qo inhibitors, QoIs) were first introduced to the market in 1996. After a short time period, isolates resistant to QoIs were detected in field populations of a range of important plant pathogens including Blumeria graminis Speer f sp tritici, Sphaerotheca fuliginea (Schlecht ex Fr) Poll, Plasmopara viticola (Berk & MA Curtis ex de Bary) Berl & de Toni, Pseudoperonospora cubensis (Berk & MA Curtis) Rost, Mycosphaerella fijiensis Morelet and Venturia inaequalis (Cooke) Wint. In most cases, resistance was conferred by a point mutation in the mitochondrial cytochrome b (cyt b) gene leading to an amino-acid change from glycine to alanine at position 143 (G143A), although additional mutations and mechanisms have been claimed in a number of organisms. Transformation of sensitive protoplasts of M fijiensis with a DNA fragment of a resistant M fijiensis isolate containing the mutation yielded fully resistant transformants, demonstrating that the G143A substitution may be the most powerful transversion in the cyt b gene conferring resistance. The G143A substitution is claimed not to affect the activity of the enzyme, suggesting that resistant individuals may not suffer from a significant fitness penalty, as was demonstrated in B graminis f sp tritici. It is not known whether this observation applies also for other pathogen species expressing the G143A substitution. Since fungal cells contain a large number of mitochondria, early mitotic events in the evolution of resistance to QoIs have to be considered, such as mutation frequency (claimed to be higher in mitochondrial than nuclear DNA), intracellular proliferation of mitochondria in the heteroplasmatic cell stage, and cell to cell donation of mutated mitochondria. Since the cyt b gene is located in the mitochondrial genome, inheritance of resistance in filamentous fungi is expected to be non-Mendelian and, therefore, in most species uniparental. In the isogamous fungus B graminis f sp tritici, crosses of sensitive and resistant parents yielded cleistothecia containing either sensitive or resistant ascospores and the segregation pattern for resistance in the F1 progeny population was 1:1. In the anisogamous fungus V inaequalis, donation of resistance was maternal and the segregation ratio 1:0. In random mating populations, the sex ratio (mating type distribution) is generally assumed to be 1:1. Therefore, the overall proportion of sensitive and resistant individuals in unselected populations is expected to be 1:1. Evolution of resistance to QoIs will depend mainly on early mitotic events; the selection process for resistant mutants in populations exposed to QoI treatments may follow mechanisms similar to those described for resistance controlled by single nuclear genes in other fungicide classes. It will remain important to understand how the mitochondrial nature of QoI resistance and factors such as mutation, recombination, selection and migration might influence the evolution of QoI resistance in different plant pathogens.

Biological Evolution↗
PubMed2003

Impact of alternative respiration and target-site mutations on responses of germinating conidia of Magnaporthe grisea to Qo-inhibiting fungicides.

Qo-inhibiting fungicides act as respiration inhibitors by binding to the Qo center of cytochrome b. Sensitivities of fungi to Qo inhibitors can be influenced by the induction of alternative respiration or by mutational changes of the cytochrome b target site. Previous studies on both mechanisms in Magnaporthe grisea (Hebert) Barr were focused on the mycelial stage of the pathogen. The present study describes the expression and impact of both resistance mechanisms during the stage of conidia germination. In the absence of a host, alternative respiration provided a >500-fold rescue from azoxystrobin during the germination of conidia derived from four wild-type isolates of M. grisea. This rescue potential during conidia gemination was substantially more pronounced than for mycelial growth. However, the pronounced effectiveness of alternative respiration during conidia germination was not apparent when barley leaves were protected with azoxystrobin prior to inoculation with conidia. In a comparison of a wild-type strain and an alternative respiration-deficient mutant, azoxystrobin efficacies in suppressing symptom development differed by a factor of two, with full disease control achieved for both genotypes at 1 microg ml(-1) azoxystrobin. In contrast, conidia derived from two QoI-resistant target site mutants were highly resistant to azoxystrobin and trifloxystrobin and fully capable of infecting leaf surfaces protected with 10 microg ml(-1) of azoxystrobin. Both target-site mutants had emerged spontaneously in the presence of high azoxystrobin doses when residual mycelial growth was supported by alternative respiration. The effective silencing of alternative respiration in protective applications of Qo-inhibiting fungicides might constitute a strategy of slowing the emergence of highly resistant target site mutants.

Acetates↗
PubMed2004

Characterization of the bound residues of the fungicide cyprodinil formed in plant cell suspension cultures of wheat.

The non-extractable residues of the fungicide cyprodinil formed in heterotrophic cell suspension cultures of wheat were studied by application of [2-pyrimidyl-14C] or [2-pyrimidyl-13C]cyprodinil. The main objective was to examine whether solid-state and liquid 13C NMR spectroscopy can be used to examine plant bound residues of pesticides. For 14C experiments, wheat suspensions grown on glucose as carbon source were treated with 10 mg litre(-1) of 14C-cyprodinil. After incubation for 12 days, 20% of applied 14C was detected as non-extractable residues. The cell debris were treated with 0.1 M HCl (reflux), 1.0 M HCl (reflux), buffer, or 2 M NaOH (50 degrees C); Björkman lignin and acidolysis lignin fractions were also prepared from the debris. Radioactivity liberated and solubilized by these procedures was examined by thin-layer chromatography and high-performance liquid chromatography. The results showed that cyprodinil and primary metabolites contributed to the fungicide's bound residues. Most of the residues (12% of applied 14C) remained associated with polar or polymeric/oligomeric endogenous cell materials in a stable manner. For the study with 13C-cyprodinil, wheat suspensions were cultivated on 13C-depleted glucose for four growth cycles, resulting in maximum 13C depletion of the natural cell components to about 0.10%. During the fourth cycle, 13C-labelled cyprodinil was applied, and cells were incubated (12 days). Cell debris was prepared and examined by solid-state 13C NMR spectroscopy. Debris was then treated as described above in the 14C experiment. Solubilized fractions were analyzed by liquid 13C NMR spectroscopy. However, none of the 13C NMR spectra recorded gave utilizable or unambiguous results, and all exhibited large inconsistencies, especially concerning the data from the conventional 14C experiment.

Binding Sites↗
PubMed2004

Alternative oxidase reduces the sensitivity of Mycosphaerella graminicola to QOI fungicides.

Forty-six (1.5%) of nearly 3000 isolates of Mycosphaerella graminicola assayed in vitro were resistant to the QOI fungicide azoxystrobin, but on sub-culturing only ten remained resistant. Cross-resistance extended to other QOIs, but varied between different isolates. In planta the resistant isolates were not well controlled, especially at lower azoxystrobin dose rates. Propyl gallate, an inhibitor of alternative oxidase, potentiated the activity of azoxystrobin in vitro so that resistance was no longer observed. The growth of resistant strains in the presence of azoxystrobin led to alternative oxidase activation. This increased flexibility in respiration allows resistant strains to survive in the presence of a QOI fungicide. Under these conditions, selection for target-site mutations can occur. Using QOIs preventatively reduces the risk of resistance since the alternative oxidase cannot by itself generate all the energy needed for germination and early infection.

Acrylates↗
PubMed2004

Synthesis and phloem mobility of acidic derivatives of the fungicide fenpiclonil.

A series of derivatives of the phenylpyrrole fungicide fenpiclonil was synthesized in which a carboxyl group was present at various sites of this non-phloem-mobile molecule. Using the Kleier model, all these acidic analogues were predicted to be moderately phloem-mobile, especially the N-substituted derivatives. One of these latter molecules, N-carboxymethyl-3-cyano-4-(2,3-dichlorophenyl)pyrrole, exhibited some fungicidal activity on the pathogenic fungus Eutypa lata, and was then tested as a phloem-mobile pesticide in the Ricinus system. The compound was indeed mobile in the sieve tubes and was not degraded to fenpiclonil in the phloem sap under our experimental conditions. Its concentration in the sap was closely correlated to the percentage of the undissociated form of the molecule in the external medium, and was similar under acidic conditions (external pH 4.6-5.0) to that of the herbicide glyphosate.

Alkynes↗
PubMed2004

Evaluation of the systemic activity of simeconazole in comparison with that of other DMI fungicides.

The systemic activity of simeconazole (RS-2-(4-fluorophenyl)-1-(1H-1,2,4-triazol-1-yl)-3-trimethylsilylpropan-2-ol) in plants was compared with those of eight other sterol demethylation inhibitor (DMI) fungicides. Simeconazole prevented the infection of Blumeria graminis (DC) Speer f sp hordei Marchal on barley leaves within a radius of several centimeters from the edge of local treatment on the leaves when the compound was separated from the leaves by glass coverslips. This reveals that simeconazole has prominent vapour-phase activity. Simeconazole showed excellent curative activity against barley powdery mildew when treated 1-3 days after inoculation. Furthermore, this indicates that simeconazole has notable translaminar activity because, when the compound was applied onto either the adaxial or abaxial leaf surface, it showed excellent efficacy against powdery mildew on the opposite side of the leaf surface of barley and cucumber. Simeconazole also showed excellent efficacy against barley powdery mildew by soil drench 24h after inoculation. This suggests that simeconazole was absorbed very quickly into the barley plant after treatment. The permeability of the compound through cuticular membranes prepared from tomato fruits was about 20% at 22 h after the treatment and was much superior to that of the other DMI fungicides tested.

Cucumis sativus↗
PubMed1995

Toxic interactions between fungicides that inhibit ergosterol biosynthesis and phosphorothioate insecticides in the male rat and bobwhite quail (Colinus virginianus).

The potential for toxic interactions between ergosterol biosynthesis-inhibiting fungicides (EBIFs), used in U.S. agriculture or clinically, and phosphorothioate insecticides was assessed in adult male rats and adult male bobwhite quail (Colinus virginianus) by measuring inhibition of plasma butyryl cholinesterase (BChE) following fungicide and insecticide treatment. Male Sprague-Dawley rats (300 g) were administered corn oil or the following EBIFs: propiconazole (400 mg/kg/day), vinclozolin (400 mg/kg/day), clotrimazole (100 mg/kg/day), or ketoconazole (100 mg/kg/day) for 3 days by oral gavage. Forty-eight hours following the final dose, a single bolus of parathion (0.4 mg/kg in corn oil) or malathion (150 mg/kg in corn oil) or corn oil alone was given po. The rats were terminated 12 hr following parathion or 4 hr following malathion dosing. Significant (p < 0.05) inhibition of BChE was observed with parathion and malathion only following clotrimazole treatment. In contrast, when a similar experiment was performed in bobwhite quail dosed with 12 mg/kg malathion following EBIF treatment, significant BChE inhibition was observed following treatment with vinclozolin or ketoconazole, but not with propiconazole or clotrimazole. Induction of cytochrome P450 in rat and quail liver by EBIFs was accompanied by enhanced oxidative desulfuration of malathion, parathion, and diazinon to toxic oxon products. Increased detoxication via oxidative dearylation/esterolytic clevage also occurred. However, while enhanced acute in vivo insecticide toxicity was observed in both species with a number of EBIF-phosphorothioate combinations, EBIF-induced oxidative activation of phosphorothioates by liver microsomes in vitro was not a good predictor of this effect.

Administration, Oral↗
PubMed1990

Expression of the blasticidin S deaminase gene (bsr) in tobacco: fungicide tolerance and a new selective marker for transgenic plants.

Blasticidin S (BS), a fungicide of microbial origin, is used for the practical control of rice blast disease. It has broad antimicrobial activity but occasionally exhibits adverse phytotoxic effects on some dicot plants. An inactivating enzyme, BS deaminase, was discovered in the BS resistant strain, Bacillus cereus K55-S1, and the structural gene, bsr, for the enzyme has been cloned. We introduced the bsr gene into tobacco plants using the Ti plasmid vector system and demonstrated that the bsr gene conferred a BS resistant phenotype to the plants. Thus the bsr gene could be useful as a selective marker for plant transformation and provides an example for a new approach to the solution of phytotoxicity problems associated with the use of some types of fungicide.

Aminohydrolases↗
PubMed1982

Selective effects of two systemic fungicides on soil fungi.

BAS 317 00F was not toxic to the total count of fungi after 2 days but was regularly significantly toxic at the three doses after 5, 20 and 40 days and toxic at the low and the high doses after 80 days. In the agar medium, it was toxic to the counts of total fungi. Aspergillus, A. terreus, Rhizopus oryzae and Mucor racemosus at the high dose. Only the mycelial growth of Trichoderma viride which was significantly inhibited by the three doses when this fungicide was added to the liquid medium. Polyram-Combi induced two effects on the total population of soil fungi. One inhibitory and this was demonstrated almost regularly after 2, 10 and 40 days and the other stimulatory after 80 days of treatment with the low and the high doses. In the agar medium, this fungicide was very toxic to total fungi and to almost all fungal genera and species at the three doses. Several fungi could survive the high dose. In liquid medium, the test fungi showed variable degree of sensitivity and the most sensitive was Gliocladium roseum which was completely eradicated by the three doses.

Culture Media↗
PubMed1987

[A method for the determination of fungicide residues in citrus and other fruit using HPLC and selective detection].

A HPLC-method is described for the determination of diphenyl, o-phenylphenol, thiabendazole, diphenylamine, and ethoxiquin in different fruits (detection limits: 0.1 mg/kg). The compounds are extracted with dichloromethane, and after concentration and filtration steps the determination is carried out by HPLC with selective detection. Chromatographic separation of fungicides is achieved by use of a RP-18 column with a methanolic formic acid buffer as eluent. The working parameters of three different HPLC-detectors (UV-, fluorimetric-, and electrochemical detector) are optimized, and it is shown that residues of the fungicides in plant materials can be determinated at least by two detectors without interferences.

Chromatography, High Pressure Liquid↗
PubMed1995

Studies on fungi associated with tomato fruits and effectiveness of some commercial fungicides against three pathogens.

Among 39 fungal species and one variety belonging to 16 genera isolated from 116 healthy tomato fruits collected from markets in Assiut, Egypt, during 1994, Aspergillus niger was found to be the most prevalent, being isolated from 84.6% of the samples. Of 11 species recovered from 156 diseased tomatoes, Alternaria alternata, Rhizopus stolonifer and A. niger were the most common and isolated from 52.7%, 35.9% and 25.0% of the samples, respectively. Experiments for comparison of the effects of medium containing tomato juice with synthetic medium on the mycelial growth of nine fungal species indicated that, the tomato juice medium was more suitable for growth of all fungal species. The effect of five commercial fungicides and sodium hypochlorite when applied as post-harvest dips after inoculation was studied in laboratory against A. alternata, A. niger and R. stolonifer. At 10 and 100 micrograms ml-1, neither of the fungicide caused a noticeable inhibition of Alternaria rot. At 1000 micrograms ml-1 benlate, rovral and sumisclex completely prevented Alternaria and Aspergillus rot, whereas cuprosan and ridomil were ineffective against rotting caused by A. niger. Rhizopus rot development was inhibited by over 50% with one treatment only (rovral at 1000 micrograms ml-1). Sodium hypochlorite has good curative properties against fruit rots especially those caused by A. alternata and A. niger.

Alternaria↗
PubMed1976

The deleterious effects of fungicides and herbicides on Xenopus laevis embryos.

Groups of 30 Xenopus laevis embryos, at "tail-bud" stage (Nieukoop-Faber stages 22-24) were exposed to 0.1-2 ppm concentrations of various pesticides for 1 to 10 days. The pesticides used were chloranil and dichlone (both are fungicidal and herbicidal); diquat (herbicide); and nabam (fungicide). The parameters examined were mortality, gross morphology, histology, and behavior. Chloranil (1.25 to 1.75 ppm) treated embryos showed abnormalities of the otolith, optic cup, and general pigmentation. Their movement was sporadically convulsive and they were unable to maintain proper balance. Dichlone (0.1 to 0.15 ppm) disrupted the development of the cephalic end of the embryo. Many of these embryos developed a slightly retarded trunk and tail only. These headless embryos lived for a time and were relatively lethargic. Diquat (0.75 to 2.0 ppm) administration reduced body size and pigmentation, and altered body shape. When embryos were treated with both 1.0 ppm of diquat and 2.0 ppm of nabam the integrity of myomeres and myocommata of the musculature was disrupted. The histological bases of these morphological and behavioral changes are discussed.

Animals↗
PubMed1991

Effect of the fungicides tridemorph and vinclozolin on soil microorganisms and nitrogen metabolism.

The effects of tridemorph and vinclozolin were studied on different types of microorganisms, urea hydrolysis and nitrification in soil and in culture. The fungicides adversely affected the population of bacteria, fungi and actinomycetes as a function of time of incubation. Urea hydrolysis both in culture and soil were also inhibited by the fungicides, and tridemorph was more detrimental. In soil, 45 micrograms/g of tridemorph inhibited 50% of ammonification of urea, ID50 for nitrite production was 750 micrograms/g. In urea-hydrolyzing cultures, 80, 75 and 77 mg/L of tridemorph were the ID50 values for urea hydrolysis by Micrococcus sp., Proteus sp. and P. vulgaris respectively.

Actinomycetales↗