A comparison of the in vitro antifungal spectra of thiophanates and benomyl

The antifungal spectra of thiophanate, thiophanate-methyl and its derivative 2-(3-methoxycarbonyl-2-thioureido) aniline (NF 48), were similar to that of benomyl. The order of effectivenessin vitro was: benomyl>NF 48> thiophanate-methyl > thiophanate, benomyl being by far the most and thiophanate by far the least active compound.The effect on mycelial growth of two fungi with an irregular inhibition pattern are presented in detail, viz. ofColletotrichum acutatum andGliocladium roseum. In the first case mycelial growth was inhibited to over 50% at low concentrations; the inhibition, however, was not further enhanced with increasing concentrations. Mycelial growth ofGliocladium roseum was maximally suppressed at low concentrations of the fungicides, whereas in this case an increase of the concentrations resulted in a decrease of inhibitory activity until a constant level had been reached. Conidiobolus eurymites, unlike the other Zygomycetes tested, proved to be sensitive to the four fungicides.Samenvatting Het fungitoxisch spectrum van de systemische fungiciden thiofanaat, thiofanaat-methyl en een derivaat hiervan, NF 48, bleek gelijk te zijn aan dat van benomyl.In vitro was de volgorde in remmende werking op de myceliumgroei: benomyl > NF 48> thiofanaat-methyl > thiofanaat. Van deze verbindingen was benomyl verreweg het meest en thiofanaat duidelijk het minst fungitoxisch. Thiofanaatmethyl en NF 48 gaven in dit opzicht slechts weinig verschil te zien.De invloed van de fungiciden op de myceliumgroei van twee schimmels met een onregelmatig remmingspatroon is weergegeven in de Fig. 1 en 2. Bij geringe concentraties van de fungiciden in het medium werd de myceliumgroei vanColletotrichum acutatum reeds tot ruim 50% geremd. Verdere toename van de fungiciden, zelfs tot zeer hoge concentraties (1000 M), had echter geen sterkere remming ten gevolge. BijGliocladium roseum bleek de myceliumgroei het sterkst geremd bij lage concentraties (bv. voor benomyl bij ca 4 M). Verhoging van de concentraties had een afname in remmende werking ten gevolge tot een niveau van 75% remming was bereikt.In tegenstelling tot de andere Zygomyceten, die tot nu toe op gevoeligheid ten aanzien van benomyl onderzocht werden, bleekConidiobolus eurymites, een saprofyt uit de bodem, gevoelig te zijn voor alle vier fungiciden.     

On the anti-cholinesterase activity of benomyl

The fungicide benomyl, previously reported to be an anti-cholinesterase and toxic to earthworms, has now been shown to have little or no effect on cholinesterase. However, it breaks down to form two products: butyl isocyanate. which is an irreversible inhibitor of the enzyme of comparable potency to organophosphates; and methyl benzimidazol-2-ylcarbamate (MBC, carbendazim), which does not inhibit at all. The reported inhibitory power of benomyl is therefore likely to be due to formation of small quantities of the former. It is also concluded that toxicity of benomyl and MBC to earthworms cannot be due to inactivation of cholinesterase.     

On a difference in the antifungal activity of tridemorph and its formulated product Calixin

The antifungal effects of tridemorph and its formulated product Calixin were compared in vitro on Ustilago maydis, Saccharomyces cerevisiae, Torulopsis candida, Botrytis allii, and Cladosporium cucumerinum. MIC values for both products were about the same. In liquid media the products were somewhat more effective than on solid media. T. candida proved sensitive only at pH 5, but the other organisms were as sensitive at pH 7 as at pH 5. Whereas tridemorph even at high concentrations did not affect oxygen consumption of these organisms, Calixin at concentrations slightly above the MIC values appeared to inhibit respiration. This effect of Calixin could be explained by the presence of Nekanil LN in the formulation. This compound inhibited both growth and respiration of the organisms at high concentrations; however, in the simultaneous presence of tridemorph a synergistic effect on oxygen consumption was observed.     

Antimicrosporidial activity of (fluoro)quinolones in vitro and in vivo

Microsporidia are a cause of emerging and opportunistic infections in humans and animals. Although two drugs are currently being used to treat microsporidiosis, concerns exist that albendazole is only selective for inhibiting some species of microsporidia that infect mammals, and fumagillin appears to have been found to be toxic. During a limited sequence survey of the Vittaforma corneae genome, a partial gene encoding for the ParC topoisomerase IV subunit was identified. The purpose of this set of studies was to determine if fluoroquinolones, which target topoisomerase IV, exert activity against Encephalitozoon intestinalis and V. corneae in vitro, and whether these compounds could prolong survival of V. corneae-infected athymic mice. Fifteen fluoroquinolones were tested. Of these, norfloxacin and ofloxacin inhibited E. intestinalis replication by more than 70% compared with non-treated control cultures, while gatifloxacin, lomefloxacin, moxifloxacin, and nalidixic acid (sodium salt) inhibited both E. intestinalis and V. corneae by at least 60% at concentrations not toxic to the host cells. These drugs were tested in vivo also, where gatifloxacin, lomefloxacin, norfloxacin, and ofloxacin prolonged survival of V. corneae-infected athymic mice (P < 0.05), whereas moxifloxacin and nalidixic acid failed to prolong survival. Therefore, these results support continued studies for evaluating the efficacy of the fluoroquinolones for treating microsporidiosis and for characterizing the target(s) of these fluoroquinolones in the microsporidia.     

In vitro and in vivo antimicrobial activity of propolis extracts against various plant pathogens

Journal of Plant Diseases and Protection - A mixture of the isolates of Fusarium graminearum, Alternaria brassicicola, Verticillium dahliae, and Pythium ultimum was examined to determine...     

In vitro antifungal activity of brassinin, camalexin and two isothiocyanates against the crucifer pathogens Alternaria brassicicola and Alternaria brassicae

In vitro assays investigated the responses of Alternaria brassicicola and A. brassicae isolates towards two crucifer phytoalexins and two isothiocyanates (ITC) by evaluating their potential toxic effects on different fungal growth parameters. Although variable responses towards each compound was observed within the species A. brassicicola , the results obtained confirmed the antifungal effects of camalexin, brassinin, allyl- (AlITC) and benzyl- (BzITC) isothiocyanates, at different developmental stages of both Alternaria species. Irrespective of the tested isolate, the phytoalexin camalexin exhibited the greater inhibitory effect with mean EC₅₀ values ranging from 34  µ m (germ-tube elongation) to 183  µ m (mycelial growth). Germ-tube elongation was more sensitive compared to conidial germination and mycelial growth, with mean EC₅₀ values of the former of 81  µ m , 520  µ m and 870  µ m for brassinin, BzITC and AlITC, respectively.     

Synthesis and antifungal activity of imidazole-1-carboxylates

A series of imidazole-1-carboxylates was prepared by reacting various alcohols with trichloromethyl chloroformate and imidazole or N,N'-carbonyl-diimidazole. They were tested for fungitoxic activity in vitro against two phytopathogenic fungi, Botrytis cinerea (grey mould) and Gibberella fujikuroi, and for preventive efficacy against grey mould on cucumber leaves. 1-(4-Substituted phenoxymethyl)-2,2-dimethylpropylimidazole-1-carboxylates showed excellent in-vitro activity against B. cinerea, and moderate activity against G. fujikuroi, and some of them also effectively controlled grey mould in vivo. A 1H-1,2,4-triazole derivative corresponding to an imidazole derivative did not have any activity, while a thiocarboxylate corresponding to an imidazole carboxylate showed excellent activity against both B. cinerea and G. fujikuroi.     

On the antifungal mode of action of tridemorph

Tridemorph (2,6-dimethyl-N-tridecylmorpholine) was active against representative of nearly all taxonomic groups of fungi; gram-positive bacteria were also sensitive although gram-negative were not. Tridemorph, 3–10 μg/ml, inhibited the multiplication of sporidia of Ustilago maydis more strongly than the increase of dry weight. The treated sporidia appeared swollen, multicellular, and sometimes branched. Unsaturated lipophilic compounds like α-tocopherol and trilinolein alleviated the toxicity of tridemorph to Botrytis allii and U. maydis. Protein and RNA syntheses were inhibited slightly. DNA synthesis was rather strongly affected already after 2 hr. Lipid synthesis was first inhibited but later stimulated. At an early stage (2 hr) treated cells differed already from control cells by a higher content of free fatty acids. Tridemorph also inhibited sterol biosynthesis. The antimicrobial spectrum, the characteristic morphology of treated cells of U. maydis, the observations on cross-resistance, the alleviating effect of unsaturated lipophilic compounds, and the alterations in neutral lipid pattern suggest strong similarity of the mode of action of tridemorph with that of the known inhibitors of sterol biosynthesis.     

Effect of some substituted benzonitriles on photosynthetic activity of spinach and wheat in vivo and in vitro

The inhibitory effects of nine nitro and/or bromo-substituted benzonitrile compounds on the photosynthetic electron flow in isolated chloroplasts and on the in vivo CO₂ fixation of spinach (Spinacia oteracea L.) and wheat (Triticum aesticum L. cv. Bezoslaya) were investigated. Bromoxynil and 3-nitro-5-hromo-4-hydroxy-bcnzonitrile were the strongest and equally effective inhibitors of Ihe in vivo CO₂ fixation of spinach, hut in wheat the nitro-bromo-compound is ineffective and 3-nitro-benzonitrile is even more inhibitory than bromoxynil. None of the substances affected DCPIPH → methylviologen reduction. In the inhibition of the DCPIP reduction only the 3,5-disuhstituted 4-hydroxy-derivatives were effective. The fact that these compounds affect only the PS II reaction with both H₂O and DPC as electron donors suggests a site of inhibition on the reducing side of PS II, between Ihe PS II reaction centre and ihe DCPIP Site. It is suggested that in the inhibition of the DCPIP reduction only steric factors are important and the different electron configuration of the sterieally similar molecules may be involved only in the absorption and translocation processes of the compounds.     

Synthesis and antifungal activity of five classes of diamines

Examples of five classes of diamines were synthesized and tested for antifungal activity. Two classes, the bis(cyclohexylmethyl)diamines and the bis(benzyl)diamines, were most effective in reducing mycelial growth of the oat leaf stripe pathogen Pyrenophora avenae Ito & Kuribay when used at a concentration of 250microM. The bis(benzyl)diamine BBD5 and the hydroxypyridylethylamine HPE2 both reduced powdery mildew infection of barley seedlings by greater than 70% when applied as a post-inoculation spray at 250 microM. Several of the compounds examined, and especially BBD5 and HPE2, reduced the formation of spermidine but greatly increased spermine levels. These changes in P avenae treated with BBD5 and HPE2 were also accompanied by greatly elevated activity of polyamine oxidase. It is suggested that the antifungal activity of these compounds may be related to the accumulation of spermine and specifically to its toxicity.     

Assay of hypocholesterolaemic agents for antifungal activity

The presence of steroids, mainly of ergosterol, in the protoplasmic membrane of fungi provides a potential target for selective antifungal action. Several nonsteroidal hypocholesterolaemic agents used in human chemotherapy were tested for fungitoxicity. Most of the compounds, especially those of the phenyl- and phenoxyalkanecarboxylic acid type (I-V) as well as the bis-aminomethyl-cyclohexane derivative (VII) revealed a moderate antifungal activity, encouraging further studies on this line.     

Metabolism of benomyl in carrot,strawberry and apple

The metabolism of benomyl was studied in carrots treated with high rates of benomyl, and in strawberries and apples treated at normal rates. The same metabolites were observed in both cases though, at normal rates, their concentrations were low but significant. Detected by means of gas-liquid chromatography they were: carbendazim, 2-aminobenzimidazole (2-AB), benzimidazole, 2-aminobenzonitrile, o-phenylene-diamine and the conjugates of carbendazim and 2-AB. o-Phenylenediamine has not hitherto been reported as a metabolite of benomyl. Two unidentified compounds were also observed by gas-liquid chromatography; their mass spectra were obtained by means of combined gas-liquid chromatography and mass spectrometry.     

In vitro analysis of host plant specificity in Rhizoctonia solani

Rhizoctonia solani is a plant pathogenic fungus with a wide host range. Host plant specificity within R. solani was analysed on seedlings grown aseptically on agar, which allowed continuous observation of both the fungus and the whole plant without disturbing the interaction. Symptom development on cauliflower, Arabidopsis , eggplant, tomato and potato by 32 R. solani isolates, belonging to six different anastomosis groups (AGs), was studied. Host plant specificity of isolates, as analysed by similarity clustering, was similar to AG-related host plant specificity as observed in the field, with AG3 isolates (except two avirulent strains) separating from the other isolates. Two R. solani isolates with a reciprocal pathogenicity on cauliflower and tomato were selected for further studies. These showed that in the pathogenic combination, R. solani isolates grew over the plant, adhered and formed infection structures, while in the nonpathogenic combination isolates grew over the plant, but neither adhesion nor the formation of infection structures occurred. From these data, it was concluded that host plant specificity is mediated in the early steps of the infection process.     

Imidazolinone inhibition of acetohydroxyacid synthase in vitro and in vivo

Imidazolinone herbicides inhibit the first enzyme of branched-chain amino acid biosynthesis, acetohydroxyacid synthase. The inhibition of the enzyme in vitro by these herbicides increases with incubation time, but is not irreversible, as deduced by reaction progress curves. In contrast to this result is the apparent irreversible inhibition of the enzyme by these imidazolinones that occurs when the herbicide is applied to intact corn plants. Plants treated with imidazolinone herbicide and then extracted showed dramatically reduced enzyme activity. This effect on extractable enzyme level occurred with several different imidazolinone herbicides in either foliar or soil application. The decrease in extractable enzyme activity could be observed within four hours after treatment. Herbicides other than imidazolinones did not reduce the extractable enzyme level. These findings suggest that the enzyme- imidazolinone interaction in vivo may be different from the interaction observed in vitro.     

Influence of artificial rainfall and washing on the benomyl and thiophanate-methyl residue content in lettuce

Experiments have been carried out to investigate the influence of artificial rainfall, applied during the growing season of lettuce in a glasshouse, and washing of the sample prior to analysis on the residue content of the crop treated with the systemic fungicides benomyl and thiophanate-methyl. The results show that if artificial rainfall is applied, treatment with a threefold dose of thiophanate-methyl, compared to benomyl, results in about the same residue content at harvest time. Applying artificial rainfall during the growing season leads to a residue level on the average 54.7% lower for benomyl and 60.2% for thiophanate-methyl compared to no sprinkling. If the sample is thoroughly rinsed with water prior to analysis the figures obtained are 34.6% with and 39.3% without artificial rainfall for benomyl and 56.9 and 71.3% respectively for thiophanate-methyl. The combined effect of both treatments is a residue content of 70.4 % less for benomyl and 88.8 % for thiophanate-methyl.     

Evaluation of benomyl and thiophanate-methyl for the control of Verticillium wilt of strawberry in the Netherlands

In pot experiments the fungicides benomyl and thiophanate-methyl controlledVerticillium wilt of strawberry when applied as a soil drench after planting. Both compounds were ineffective as foliar sprays and as root dips prior to planting. Soil drenches applied to commercially grown runner plants in the waiting field (August) and to the same plants in the greenhouse (December or January) increased the yield. On infested ground, a soil drench with thiophanate-methyl promoted the occurrence of crown rot caused byPhytophthora cactorum.     

Plant-pathogen interactions of sunflower and Macrophomina phaseolina in vitro and in vivo

The relative pathogenicity of isolates of Macrophomina phaseolina was comparable both on sunflower tissue cultures and on mature plants and seedlings. The relative susceptibility of the different sunflower lines in vitro showed a similar pattern for cotyledon callus cultures, but not for immature embryo cultures. Although these protocols appear to be unsuitable for the selection of novel disease resistance, they do offer the potential for a rapid, non-destructive screen for resistant material.     

Synthesis and in-vitro antifungal activity of 6-trifluoromethylpyrazolo[3,4-d]pyrimidines

Thirty 6-trifluoromethylpyrazolo[3,4-d]pyrimidines were synthesised and tested for antifungal activity in vitro against ten phytopathogenic fungi of different taxonomic classes. Six of the compounds had noteworthy activity against Sclerotinia minor, Corticium solani and Phoma betae. The relationships between structure and activity are discussed on the basis of the present and previous studies.     

产几丁质酶菌的分离鉴定及其抑菌作用的初步研

从北京地区的土样、砂样和水样中分离并纯化了产生几丁质酶的菌株，其中CT14含几丁质酶活性最高，经对其细胞形态、菌落特征的观察和生化特性检测，证明该菌株是环状芽孢杆菌(Bacillus circulans)。其几丁质酶粗提液能抑制多种植物病原真菌的生长，表明它对植物病原真菌的拮抗作用具有广谱性。     

The effect of benomyl and thiophanate-methyl on earthworm populations in apple orchards

The use of the fungicides benomyl and thiophanate-methyl on experimental orchard plots for 3 years and of benomyl on a commercial orchard for 1 year resulted in a drastic reduction of earthworm populations. The species of earthworms affected were Lumbricus terrestris, L. castaneus, L. festivus, L. rubellus, Allolobophora caliginosa, A. chlorotica, A., longa, A. rosea, A. tuberculata and Octolasium cyaneum. L. terrestris and A. chlorotica were more affected than the other species, both being virtually eliminated after 2 years' spraying. The depleted populations of species other than L. terrestris and A. chlorotica recovered to normal levels after a 2-year rest period following a single year's treatment with benomyl (1.40 kg/ha). The role of the surface-feeding L. terrestris is discussed in relation to the spray fall-out on the sward and to grass management.