Presence Of Propiconazole Research Articles

Baseline sensitivity and fungicidal action of propiconazole against Penicillium digitatum

Green mold, caused by Penicillium digitatum, is the most important citrus postharvest disease worldwide and often causes substantial economic losses to the citrus industry. The demethylation inhibitor (DMI) fungicides are highly effective against a broad range of fungal pathogens, but the DMI fungicide propiconazole has not been registered yet in China for the control of citrus green mold. In this study, baseline sensitivity of P. digitatum to propiconazole was determined. The frequency distribution of logarithms of EC50 values for 118 isolates collected from five regions in China was bimodal, and among the 118 isolates, 18 isolates were less sensitive or had low resistance to propiconazole. The mean EC50 value of the sensitive 100 isolates was 0.104 mg/L. Preventive control efficacies on Satsuma mandarin for propiconazole at 200 and 400 mg/L were 63.1 and 84.3%, respectively. The fruit treated with propiconazole at 40 and 100 mg/L produced significantly fewer conidia, and the virulence of the conidia decreased by 12.3 and 14.8%, respectively. Studies with propidium iodide showed that the membrane integrity was damaged for 25.6% of conidia produced on PDA amended with propiconazole at 0.1 mg/L. Fluorescence microscopy observations of P. digitatum conidia stained with 2,7-dichlorofluorescin showed that propiconazole significantly induced the generation of intracellular reactive oxygen species (ROS). Compared with the sensitive isolates, no point mutations were detected in either the coding or promoter region of the target gene CYP51A of the isolates with low resistance to propiconazole. However, the relative expression levels of CYP51A for three resistant isolates were higher than sensitive isolates, and the mean relative expression was 2.08 for resistant isolates versus 0.62 for sensitive isolates in the absence of propiconazole and 3.12 versus 1.44 in the presence of propiconazole. These results indicate increased expression of CYP51A is the molecular mechanism for low resistance of P. digitatum to propiconazole.

In vitro and in vivo evidence for the inhibition of brassinosteroid synthesis by propiconazole through interference with side chain hydroxylation

ABSTRACTWe carried out the biochemical evaluation of the target site of propiconazole in BR biosynthesis. Applying BR biosynthesis intermediates to Arabidopsis seedlings grown in the presence of propiconazole under dark condition, we found that the target site of propiconazole in BR biosynthesis can be identified among the C22 and C23 side chain hydroxylation steps from campestanol to teasterone. Using differential spectra techniques to determine the binding affinity of propiconazole to CYP90D1, which is responsible for C23 hydroxylation of BR, we found that propiconazole induced typical type II binding spectra in response to purified recombinant CYP90D1 and the Kd value was found approximately 0.76 μM.

The synergistic potential of the azole fungicides prochloraz and propiconazole toward a short α-cypermethrin pulse increases over time in Daphnia magna

Pyrethroid insecticides are highly toxic to non-target aquatic invertebrates. Their high toxicity is synergized when co-occurring with azole fungicides in the aquatic environment. Little is known about the importance of synergy, when pyrethroids only occur during a short pulse of a few hours, as it is likely to happen in the environment, nor about the persistence of synergy over time. This study analyzed the synergistic potential of the fungicides propiconazole and prochloraz toward Daphnia magna, when exposed to a pulse (7.2h) of α-cypermethrin at different concentrations (average pulse concentrations 0.07–11nM). Immobilization was monitored during exposure and a subsequent recovery period (87.5h) with and without continuous co-exposure to the azoles (1.4 and 1.7μM, respectively). EC50 values for immobilization decreased exponentially over time with a higher rate in the presence of the azoles. EC50 values for α-cypermethrin determined at the end of the experiment were 3.3±0.5nM in the absence of azoles and 0.26±0.04, and 0.08±0.01nM in the presence of propiconazole and prochloraz, respectively. The synergistic potential of the azoles was strongly dependent on time: no synergism could be detected during the pulse, but with azole co-exposure EC50 values decreased during the recovery period by a factor of up to 13 (propiconazole) and 61 (prochloraz) compared to values without azole exposure. Such high synergistic ratios have not been reported for pesticide mixtures in literature before. Our findings highlight that a pulse of the pyrethroid α-cypermethrin is synergized far beyond the actual pulse and beyond standardized test durations. Long post-exposure times are therefore mandatory in order to capture full synergism.

A pleiotropic drug resistance transporter is involved in reduced sensitivity to multiple fungicide classes in Sclerotinia homoeocarpa (F.T. Bennett).

Dollar spot, caused by Sclerotinia homoeocarpa, is a prevalent turfgrass disease, and the fungus exhibits widespread fungicide resistance in North America. In a previous study, an ABC-G transporter, ShatrD, was associated with practical field resistance to demethylation inhibitor (DMI) fungicides. Mining of ABC-G transporters, also known as pleiotropic drug resistance (PDR) transporters, from RNA-Seq data gave an assortment of transcripts, several with high sequence similarity to functionally characterized transporters from Botrytis cinerea, and others with closest blastx hits from Aspergillus and Monilinia. In addition to ShatrD, another PDR transporter showed significant over-expression in replicated RNA-Seq data, and in a collection of field-resistant isolates, as measured by quantitative polymerase chain reaction. These isolates also showed reduced sensitivity to unrelated fungicide classes. Using a yeast complementation system, we sought to test the hypothesis that this PDR transporter effluxes DMI as well as chemically unrelated fungicides. The transporter (ShPDR1) was cloned into the Gal1 expression vector and transformed into a yeast PDR transporter deletion mutant, AD12345678. Complementation assays indicated that ShPDR1 complemented the mutant in the presence of propiconazole (DMI), iprodione (dicarboximide) and boscalid (SDHI, succinate dehydrogenase inhibitor). Our results indicate that the over-expression of ShPDR1 is correlated with practical field resistance to DMI fungicides and reduced sensitivity to dicarboximide and SDHI fungicides. These findings highlight the potential for the eventual development of a multidrug resistance phenotype in this pathogen. In addition, this study presents a pipeline for the discovery and validation of fungicide resistance genes using de novo next-generation sequencing and molecular biology techniques in an unsequenced plant pathogenic fungus.

Induced overexpression of cytochrome P450 sterol 14α-demethylase gene (CYP51) correlates with sensitivity to demethylation inhibitors (DMIs) inSclerotinia homoeocarpa

The fungus Sclerotinia homoeocarpa causes dollar spot, the most important turfgrass disease worldwide. Demethylation inhibitor (DMI) fungicides have been relied upon heavily to manage this disease. Presently, populations of S. homoeocarpa with reduced sensitivity or resistance to DMIs are widespread in the United States. Cytochrome P450 sterol 14α-demethylase (ShCYP51) and its flanking regions were identified and sequenced in 29 isolates of S. homoeocarpa with a range of DMI sensitivities. No modifications were found in the gene coding and upstream regions that were consistently related to DMI sensitivity. In the absence of propiconazole, ShCYP51 was expressed at a similar low level among DMI baseline and resistant isolates. In the presence of propiconazole, DMI-resistant isolates were induced to express ShCYP51 at significantly higher levels than baseline isolates by propiconazole at 5 mg L(-1) for 5 h or at 0.5 mg L(-1) for 72 h. The ShCYP51 expression level after 72 h exposure to 0.5 mg L(-1) of propiconazole was linearly related to EC50 values and ΔRG (the change in relative growth rate over time), with R(2) values equal to 83.7 and 90.0% respectively. Induced overexpression of ShCYP51 in resistant isolates following DMI exposure is an important factor determining DMI sensitivity in S. homoeocarpa.

Study on the Binding of Propiconazole to Protein by Molecular Modeling and a Multispectroscopic Method

Propiconazole (PCZ) is an N-substituted triazole used as a fungicide on fruits, grains, seeds, hardwoods, and conifers. Although the triazole fungicides have shorter half-lives and lower bioaccumulation than the organochlorine pesticides, possible detrimental effects on the aquatic ecosystem and human health also exist. To evaluate the toxicity of PCZ at the protein level, its effects on human serum albumin (HSA) were characterized by molecular modeling and multispectroscopic method. On the basis of the fluorescence spectra, PCZ exhibited remarkable fluorescence quenching, which was attributed to the formation of a complex. The thermodynamic parameters ΔH and ΔS were calculated to be -14.980 KJ/mol and 26.966 J/(mol K), respectively, according to the van't Hoff equation, which suggests hydrophobic and electrostatic interactions are the predominant intermolecular forces in stabilizing the PCZ-protein complex. Furthermore, HSA conformation was slightly altered in the presence of PCZ. These results indicated that PCZ indeed affected the conformation of HSA.

Factors Affecting the Development of Wood Rot on Lemon Trees Infected with Antrodia sinuosa, Coniophora eremophila, and a Nodulisporium sp.

Brown heartwood rot, which often is found in branches within lemon groves in southwestern Arizona, is caused by two basidiomycete fungi, Antrodia sinuosa and Coniophora eremophila. Another fungus, a species of Nodulisporium, has been recovered from small, dying lemon tree branches with an internal white wood rot. Studies were conducted from 1999 through 2002 to compare the extent of wood decay caused by these fungi (i) on lemon tree branches at different times of the year, (ii) on different types of citrus, (iii) on some desert woody perennial plants, and (iv) on lemon tree branches treated with selected fungicides. The mean length of wood decay columns recorded in lemon tree branches inoculated with A. sinuosa, C. eremophila, and the Nodulisporium sp. during the time periods of November to January, February to April, May to July, and August to October was 2.9, 4.7, 13.3, and 15.2 cm, respectively. There was a significant linear correlation between the length of wood decay columns and air temperature for all three pathogens. The mean length of wood decay columns for all time periods in branches inoculated with A. sinuosa, C. eremophila, and the Nodulisporium sp. was 11.8, 5.8, and 9.6 cm, respectively. In two trials, wood decay columns were significantly greater on Lisbon lemon tree branches inoculated with A. sinuosa compared with those on Marsh grapefruit and Valencia orange trees inoculated with the same pathogen. Wood decay in the presence of the Nodulisporium sp. was greater on branches of lemon compared with grapefruit trees in two trials and on lemon compared with orange trees in one of two trials. With the exception of C. eremophila on creosote bush, each of the three wood rot pathogens caused some wood decay in branches of velvet mesquite, salt cedar, Mexican palo verde, and creosote bush, four common desert perennials found in southwestern Arizona. Compared with nontreated but inoculated lemon trees, the length of wood decay columns in branches inoculated with A. sinuosa, C. eremophila, and the Nodulisporium sp. in the presence of propiconazole was reduced by 79, 94, and 92%, respectively, and, in the presence of azoxystrobin, was suppressed by 71, 80, and 89%, respectively. Current management guidelines focus on minimizing branch fractures and other nonpruning wounds in conjunction with early detection and removal of infected branches before the onset of the increased wood decay development period extending from May to October.

Synthesis of nuclear lipids in L 2C leukemic lymphocytes

We previously reported that propiconazole strongly inhibits cholesterol synthesis, but not cell division in a stimulated cell, the human lymphocyte cultured with phytohemagglutinin, showing that newly synthesized cholesterol is not necessary for cell division. In this study we labeled the L2C leukemic guinea pig lymphocyte, a naturally stimulated cell, with [2-14C]acetate, and compared the composition of newly synthesized lipids isolated from nuclei and whole cells (or microsomes). We observed that the proportion of cholesterol in labeled non-saponifiable lipids extracted from nuclei was lower than in non-saponifiable lipids isolated from whole cells, whereas the proportion of squalene and polar lipids was higher. By analyzing total lipid extracts, the polar lipids were identified as alkylglycerols, and the above mentioned distribution of constituents was confirmed. The identification of alkylglycerols was also supported by the comparison of radioactive lipid composition after labeling cells with three different lipid precursors: [2-14C]mevalonate, [2-14C]acetate and [2-14C]stearate. When cells were labeled in the presence of dodecylimidazole, the percentage of squalene and alkylglycerols decreased in nuclear lipids, but was not altered when cells were cultured in the presence of propiconazole, a cholesterol synthesis inhibitor which does not affect cell division of human stimulated lymphocytes. We have shown that dodecylimidazole inhibited alkylglycerol biosynthesis and squalene uptake by the nucleus, suggesting that these compounds could play a role in the regulation of cell division.

Effect of propiconazole on growth and sterol biosynthesis by Sclerotium rolfsii

Germination of sclerotia ofSclerotium rolfsii on agar nutrient medium was delayed or slightly inhibited by concentrations of propiconazole between 0.4 and 4.0 μg ml−1, but was strongly inhibited by 8 μg ml−1 and completely inhibited by 16 μg ml−1. On the other hand, growth of hyphae from the germinated sclerotia was strongly inhibited by propiconazole at 1 μg ml−1 or greater. Hyphal growth from agar discs on agar medium was about 8 times less sensitive than hyphal growth from the sclerotia or from hyphal inoculum in liquid media. Propiconazole at 0.25 and 1.0 μg ml−1 strongly inhibited ergosterol biosynthesis, but this was not associated with large accumulations of C-14 methyl sterols. The ratio of eburicol to ergosterol in hyphae grown in the presence of 0.25 μg ml−1 propiconazole for 16, 30 or 45 h was 0.11, 0.13 and 0.04, respectively, for the three intervals while for hyphae grown in the presence of 1 μg ml−1, the ratios were 0.29, 0.36 and 0.30, respectively, for the same intervals. In view of a ratio of 23.5 for14C-acetate incorporation into the two sterols during the initial 6 h growth period in the presence of propiconazole, it is believed that the lack of large accumulation of C-14 methyl sterols is due to the feedback inhibition by eburicol or to cell lysis when the content of ergosterol becomes too low in the actively growing cells.