The hydroxyanilide fenhexamid, a new sterol biosynthesis inhibitor fungicide efficient against the plant pathogenic fungus Botryotinia fuckeliana (Botrytis cinerea)

Carrier-free self-assembled nanoparticles based on prochloraz and fenhexamid for reducing toxicity to aquatic organism

Nanoformulations of pesticides are an effective way to increase utilization efficiency and alleviate the adverse impacts on the environments caused by conventional pesticide formulations. However, the complex preparation process, high cost, and potential environmental risk of nanocarriers severely restricted practical applications of carrier-based pesticide nanoformulations in agriculture. Herein, carrier-free self-assembled nanoparticles (FHA-PRO NPs) based on fenhexamid (FHA) and prochloraz (PRO) were developed by a facile co-assembly strategy to improve utilization efficiency and reduce toxicity to aquatic organism of pesticides. The results showed that noncovalent interactions between negatively charged FHA and positively charged PRO led to core-shell structured nanoparticles arranged in an orderly manner dispersing in aqueous solution with a diameter of 256 nm. The prepared FHA-PRO NPs showed a typical pH-responsive release profile and exhibited excellent physicochemical properties including low surface tension and high max retention. The photostability of FHA-PRO NPs was improved 2.4 times compared with free PRO. The FHA-PRO NPs displayed superior fungicidal activity against Sclerotinia sclerotiorum and Botrytis cinerea and longer duration against Sclerotinia sclerotiorum on potted rapeseed plants. Additionally, the FHA-PRO NPs reduced the acute toxicity of PRO to zebrafish significantly. Therefore, this work provided a promising strategy to develop nanoformulations of pesticides with stimuli-responsive controlled release characteristics for precise pesticide delivery.

Genotypic and phenotypic characterization of resistance to fenhexamid, carboxin, and, prochloraz, in Botrytis cinerea isolates collected from cut roses in Colombia

Gray mold, caused by Botrytis sp., is a significant disease in Colombian rose crops and its control depends primarily on the intensive use of chemically synthesized fungicides. Despite the importance of this pathogen, there is limited information in Colombian floriculture about molecular taxonomy of species, fungicide resistance of populations and their genetic mechanism of resistance. In this study, we analyze 12 isolates of this fungus collected from rose-producing crops in the Department of Cundinamarca and conducted phylogenetic analysis using HSP60, G3PDH, and RPB2 gene sequences. Additionally, we realize phenotypic and genotypic characterization of resistance to the fungicides fenhexamid, carboxin, and prochloraz, evaluating the in vitro EC50 and presence of mutations of target genes of each isolate. All isolates were characterized as Botrytis cinerea in the phylogenetic analysis and presents different levels of resistance to each fungicide. These levels are related to mutations in target genes, with predominancy of L195F and L400F in the ERG27 gene to fenhexamid resistance, H272R/Y in the SDHB gene for carboxin resistance, and Y136F in the CYP51 gene for prochloraz resistance. Finally, these mutations were not related to morphological changes. Collectively, this knowledge, presented for the first time to the Colombian floriculture, contribute to a better understanding of the genetic diversity and population of B. cinerea from rose-producing crops in the department of Cundinamarca, and serve as a valuable tool for making informed decisions regarding disease management, future research, and improving crop management and sustainability in the Colombian floriculture industry.

Sterol Biosynthesis Contributes to Brefeldin-A-Induced Endoplasmic Reticulum Stress Resistance in Chlamydomonas reinhardtii

The endoplasmic reticulum (ER) stress response is an evolutionarily conserved mechanism in most eukaryotes. In this response, sterols in the phospholipid bilayer play a crucial role in controlling membrane fluidity and homeostasis. Despite the significance of both the ER stress response and sterols in maintaining ER homeostasis, their relationship remains poorly explored. Our investigation focused on Chlamydomonas strain CC-4533 and revealed that free sterol biosynthesis increased in response to ER stress, except in mutants of the ER stress sensor Inositol-requiring enzyme 1 (IRE1). Transcript analysis of Chlamydomonas experiencing ER stress unveiled the regulatory role of the IRE1/basic leucine zipper 1 pathway in inducing the expression of ERG5, which encodes C-22 sterol desaturase. Through the isolation of three erg5 mutant alleles, we observed a defect in the synthesis of Chlamydomonas' sterol end products, ergosterol and 7-dehydroporiferasterol. Furthermore, these erg5 mutants also exhibited increased sensitivity to ER stress induced by brefeldin A (BFA, an inhibitor of ER-Golgi trafficking), whereas tunicamycin (an inhibitor of N-glycosylation) and dithiothreitol (an inhibitor of disulfide-bond formation) had no such effect. Intriguingly, the sterol biosynthesis inhibitors fenpropimorph and fenhexamid, which impede steps upstream of the ERG5 enzyme in sterol biosynthesis, rescued BFA hypersensitivity in CC-4533 cells. Collectively, our findings support the conclusion that the accumulation of intermediates in the sterol biosynthetic pathway influences ER stress in a complex manner. This study highlights the significance and complexity of regulating sterol biosynthesis during the ER stress response in microalgae.

Chilean Botrytis cinerea Isolates with Reduced Sensitivity to Fludioxonil Exhibit Low to Null Fitness Penalties

The main phytosanitary problem for table grape production in Chile is gray mold caused by the fungus Botrytis cinerea. To manage this issue, the primary method utilized is chemical control. Fludioxonil, a phenylpyrrole, is highly effective in controlling B. cinerea and other plant pathogens. Consistently, there have been no field reports of reduced efficacy of fludioxonil; however, subpopulations with reduced sensitivity to fludioxonil are on the rise globally, as per increasing reports. Our study involved a large-scale evaluation of B. cinerea's sensitivity to fludioxonil in the Central Valley of Chile's primary table grape production area during the growing seasons from 2015 to 2018. Out of 2,207 isolates, only 1.04% of the isolates (n = 23) exceeded the sensitivity threshold value of 1 μg/ml. Remarkably, 95.7% are concentrated in a geographic region (Valparaíso Region). Isolates with reduced sensitivity to fludioxonil showed growth comparable with sensitive isolates and even more robust growth under nutritional deficit, temperature, or osmotic stress, suggesting greater environmental adaptation. When table grape detached berries were stored at 0°C, isolates less sensitive to fludioxonil caused larger lesions than sensitive isolates (2.82 mm compared with 1.48 mm). However, the lesions generated by both types of isolates were equivalent at room temperature. This study found no cross-resistance between fludioxonil and fenhexamid, an essential fungicide integrated with fludioxonil in Chilean B. cinerea control programs. All the Chilean isolates with reduced sensitivity to fludioxonil were controlled by the fludioxonil/cyprodinil mixture, a commonly employed form of fludioxonil. The cyprodinil sensitivity in the isolates with reduced sensitivity to fludioxonil explains their low field frequency despite their null fitness penalties. However, the emergence of fludioxonil-resistant isolates inside the Chilean B. cinerea population demands a comprehensive analysis of their genetic bases, accompanied by monitoring tools that allow the permanence of field fludioxonil efficacy.

The antifungal potential of the chelating agent EDTA against postharvest plant pathogen Botrytis cinerea

Botrytis cinerea is a phytopathogenic fungus that causes gray mold, a major postharvest disease of fruits and vegetables. Chemical fungicides remain the main solution to control Botrytis disease, but concerns have raised about their safety to environment and human health, and there is an increasing need for development of more effective and less toxic treatments. In this study the divalent cation chelating agent ethylenediaminetetraacetic acid (EDTA) exhibited marked antifungal activity against B. cinerea, including inhibition of spore germination, mycelial growth, infection cushion formation, stimulation of cell death, and impairment of fungal virulence. These adverse effects of EDTA could be reversed by the addition of calcium ion, implying that metal ion chelation is involved in the fungicidal mechanism. Bean leaf and tomato fruit protection assay indicated that EDTA treatment led to a significant reduction of infection by B. cinerea. Furthermore, the antifungal activity of EDTA was significantly enhanced when used in combination with fenhexamid. These findings suggest that EDTA could be a promising tool to control B. cinerea, and application of EDTA may reduce the use of conventional chemical fungicides.

Identification and structural elucidation of bioactive compounds from Scirpoides holoschoenus

Phytochemical investigations of dichloromethane and methanol extracts of roots and rhizomes of Scirpoides holoschoenus afforded 21 stilbenes, six flavonoids, six ferulic acid derivatives and four diterpenes. Among these constituents, six stilbenes, one flavonoid, one diterpene and two ferulic acid derivatives, represent previously unreported natural products. Structure elucidation was performed by HRESI-MS, NMR, GC-MS, and ECD data evaluation. The monoprenylated flavonoid (sophoraflavanone B) and all isolated stilbene oligomers (trans-scirpusin B, scirpusin A, cassigarol E, cyperusphenol B, cyperusphenol D, passiflorinol A, cyperusphenol A and mesocyperusphenol A) showed strong inhibitory activities on spore germination of two Botrytis cinerea strains isolated from field-infected grape berries and apple fruits compared to the reference controls resveratrol, piceid, and fenhexamid at a test concentration of 2.0 mM. For sophoraflavanone B and cyperusphenol A, the EC₅₀ values were determined by concentration response curves and resulted in values of 0.35 mM and 0.53 mM, respectively. The data suggest that stilbene oligomers but also prenylated flavonoids should be examined further to gain more information on their antimicrobial activity and might be a suitable addition to chemical fungicides on the market to combat gray mold.

Inhibiting C-4 Methyl Sterol Oxidase with Novel Diazaborines to Target Fungal Plant Pathogens

With resistance to current agricultural fungicides rising, a great need has emerged for new antifungals with unexploited targets. In response, we report a novel series of diazaborines with potent activity against representative fungal plant pathogens. To identify their mode of action, we selected for resistant isolates using the model fungus Saccharomyces cerevisiae. Whole-genome sequencing of independent diazaborine-resistant lineages identified a recurring mutation in ERG25, which encodes a C-4 methyl sterol oxidase required for ergosterol biosynthesis in fungi. Haploinsufficiency and allele-swap experiments provided additional genetic evidence for Erg25 as the most biologically relevant target of our diazaborines. Confirming Erg25 as putative target, sterol profiling of compound-treated yeast revealed marked accumulation of the Erg25 substrate, 4,4-dimethylzymosterol and depletion of both its immediate product, zymosterol, as well as ergosterol. Encouraged by these mechanistic insights, the potential utility of targeting Erg25 with a diazaborine was demonstrated in soybean-rust and grape-rot models of fungal plant disease.

Inhibition of SC4MOL and HSD17B7 shifts cellular sterol composition and promotes oligodendrocyte formation

While the cholesterol biosynthesis pathway has been extensively studied, recent work has forged new links between inhibition of specific sterol pathway enzymes, accumulation of their unique sterol substrates, and biological areas as diverse as cancer, immunology, and neurodegenerative disease. We recently reported that dozens of small molecules enhance formation of oligodendrocytes, a glial cell type lost in multiple sclerosis, by inhibiting CYP51, Sterol 14-reductase, or EBP and inducing cellular accumulation of their 8,9-unsaturated sterol substrates. Several adjacent pathway enzymes also have 8,9-unsaturated sterol substrates but have not yet been evaluated as potential targets for oligodendrocyte formation or in many other biological contexts, in part due to a lack of available small-molecule probes. Here, we show that genetic suppression of SC4MOL or HSD17B7 increases the formation of oligodendrocytes. Additionally, we have identified and optimized multiple potent new series of SC4MOL and HSD17B7 inhibitors and shown that these small molecules enhance oligodendrocyte formation. SC4MOL inhibitor CW4142 induced accumulation of SC4MOL's sterol substrates in mouse brain and represents an in vivo probe of SC4MOL activity. Mechanistically, the cellular accumulation of these 8,9-unsaturated sterols represents a central driver of enhanced oligodendrocyte formation, as exogenous addition of purified SC4MOL and HSD17B7 substrates but not their 8,9-saturated analogs promotes OPC differentiation. Our work validates SC4MOL and HSD17B7 as novel targets for promoting oligodendrocyte formation, underlines a broad role for 8,9-unsaturated sterols as enhancers of oligodendrocyte formation, and establishes the first high-quality small molecules targeting SC4MOL and HSD17B7 as novel tools for probing diverse areas of biology.

In vitro metabolism of tebuconazole, flurtamone, fenhexamid, metalaxyl-M and spirodiclofen in Cannabis sativa L. (hemp) callus cultures

BACKGROUND

Cannabis sativa L. (hemp) is a medicinal plant producing various cannabinoids. Its consumption is legalized for medical use due to the alleged positive health effects of these cannabinoids. To satisfy the demand, C. sativa plants are propagated in contained growth chambers. During indoor propagation, pesticides usually are used to ensure efficient production. However, pesticide registration and safe application in C. sativa has not been investigated in detail.

RESULTS

With this study the metabolic degradation of pesticides in recently established C. sativa callus cultures was examined. Tebuconazole, metalaxyl-M fenhexamid, flurtamone and spirodiclofen were applied at 10 μm for 21 days. Results were compared with metabolism data obtained from Brassica napus L., Glycine max (L.) Merr., Zea mays L. and Tritium aestivum L. callus cultures as well as in metabolism guideline studies. The successfully established C. sativa callus cultures were able to degrade pesticides by oxidation, demethylation, and cleavage of ester bonds in phase I, as well as glycosylation and conjugation with malonic acid in phase II and III. Initial metabolites were detected after Day (D)7 and were traced at D21.

CONCLUSION

The resulting pathways demonstrate the same main degradation strategies as crop plants. Because metabolites could be the main residue, the exposure of consumers to these residues will be of high importance. We present here an in vitro assay for a first estimation of pesticide metabolism in C. sativa. © 2021 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Molecular identification and characterization of Botrytis cinerea associated to the endemic flora of semi-desert climate in Chile

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For the first time was detected the presence of B. cinerea on fourteen new host plant.

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We provide evidence for phenotype and genotype diversity in these B. cinerea isolates, where 83.3% of the isolates presented both transposable elements, boty and flipper.

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We found in this study, that some isolates of this fungus lose the ability to produce conidia or sclerotia formation and revealed a great diversity among the isolates concerning both features.

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The 16.6% of the isolates of B. cinerea showed substantially reduced virulence.

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According to fungicide resistance studies the results indicate that resistance to Fenhexamid or Boscalid was observed in the 22.6% of isolates.

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These findings are of great epidemiological importance to several regions, because of the distribution and the possible ecological impact of this disease on native and endemic plants in Chile.

Botrytis cinerea is a phytopathogenic fungus that infects over 200 plant species and can cause significant crop losses in local and worldwide agricultural industries. However, its presence in the endemic flora in the Coquimbo Region and its impact on local flora have not been studied yet. In order to determine whether Botrytis spp is present in the native plant in the Coquimbo Region, fifty-two field-samples were analysed. A total of 30 putative Botrytis spp were isolated and phenotypic and genetically characterized. The internal transcribed spacer (ITS) analysis of these isolates revealed that it corresponded to genus Botrytis. For further confirmation, nuclear protein-coding genes (G3PDH, HSP60, and RPB2) were sequenced and showed 100% identity against B. cinerea. Complementary to this, Botrytis can also be clustered in two different groups, group I (B. pseudocinerea) and group II (B. cinerea), based on DNA polymorphism, the Botrytis isolates were identified as member of group II. On the order hand, we investigated the presence and frequency distribution of the transposable elements boty and flipper in the isolates obtained. The results indicate that 83.3% of the isolates presented both transposable elements, boty and flipper, indicating that the most prevalent genotype was transpose. In addition, 16.6% of the isolates showed substantially reduced virulence in apple fruit in comparison to B05.10 strain. According to fungicide resistance studies, the results indicate that resistance to Fenhexamid or Boscalid was observed in the 22.6% of isolates. The results show for the first time that B. cinerea has not been described before in fourteen new host plants and contributes to our fundamental understanding of the presence of B. cinerea in the native plant in the Coquimbo Region and the possible ecological impact of this disease on native and endemic plants.

Modulation of lanosterol synthase drives 24,25-epoxysterol synthesis and oligodendrocyte formation

Small molecules that promote the formation of new myelinating oligodendrocytes from oligodendrocyte progenitor cells (OPCs) are potential therapeutics for demyelinating diseases. We recently established inhibition of specific cholesterol biosynthesis enzymes and resulting accumulation of 8,9-unsaturated sterols as a unifying mechanism through which many such molecules act. To identify more potent sterol enhancers of oligodendrocyte formation, we synthesized a collection of 8,9-unsaturated sterol derivatives and found that 24,25-epoxylanosterol potently promoted oligodendrocyte formation. In OPCs, 24,25-epoxylanosterol was metabolized to 24,25-epoxycholesterol via the epoxycholesterol shunt pathway. Increasing flux through the epoxycholesterol shunt using genetic manipulation or small-molecule inhibition of lanosterol synthase (LSS) increased endogenous 24,25-epoxycholesterol levels and OPC differentiation. Notably, exogenously supplied 24,25-epoxycholesterol promoted oligodendrocyte formation despite lacking an 8,9-unsaturation. This work highlights epoxycholesterol shunt usage, controlled by inhibitors of LSS, as a target to promote oligodendrocyte formation. Additionally, sterols beyond the 8,9-unsaturated sterols, including 24,25-epoxycholesterol, drive oligodendrocyte formation.

Fungicide Resistance Profiles of Botrytis cinerea Isolates From Michigan Vineyards and Development of a TaqMan Assay for Detection of Fenhexamid Resistance

Botrytis cinerea on grapes causes bunch rot at both pre- and postharvest stages, in which losses can reach up to 100%. Chemical control primarily relies on the prophylactic use of site-specific fungicides. Repeated applications of these products raise the risk of fungicide resistance development in B. cinerea populations, which can result in disease control failures. To determine the extent of resistance, B. cinerea isolates were collected from grape clusters in the northwest and southwest grape growing regions of Michigan in 2014 and 2018 (n = 115 and 125, respectively). These isolates were phenotyped using discriminatory doses of eight fungicides to determine the levels of resistance. Fungicide resistance increased from 2014 to 2018, mostly affecting the active ingredients fenhexamid, fluopyram, and iprodione. B. cinerea isolates resistant to multiple fungicides were detected in 2014 and 2018, with a higher frequency of resistance in 2018. TaqMan real-time PCR has been developed to detect B. cinerea fungicide resistance to fenhexamid and to differentiate the erg27 F412S/I/V alleles. The TaqMan assay was tested for sensitivity, specificity, and reproducibility on purified DNA and infected grape tissue samples. Our data provide essential information to growers about the efficacy for B. cinerea control using the available botryticides. Furthermore, the developed fenhexamid markers will be transferred to diagnostic clinics to assist growers in the management of bunch rot before resistance-related control failures occur.

Evaluation of Callus Cultures to Elucidate the Metabolism of Tebuconazole, Flurtamone, Fenhexamid, and Metalaxyl-M in Brassica napus L., Glycine max (L.) Merr., Zea mays L., and Triticum aestivum L

Plant cell cultures can be used to identify the metabolic degradation of pesticides in crops. Therefore, Brassica napus L., Glycine max (L.) Merr., Zea mays L. and Triticum aestivum L. were used to elucidate the metabolic degradation of the following pesticides: tebuconazole, flurtamone, fenhexamid, and metalaxyl-M. Callus cultures were treated with 10 μM of the named pesticides by passive diffusion out of the nutrition agar while young plants were hydroponically exposed to it. After 14 days, the comparison of in planta and in vitro experiments showed that the metabolic degradation is well described by in vitro callus cultures. The intracellular uptake of all pesticides and a broad spectrum of exemplarily hydroxylated and conjugated metabolites were detectable. Overall, the comparability of the nature of residues out of both experiments with the regulatory guideline metabolism studies could be demonstrated. Therefore, we recommend it as a potential screening tool to elucidate the metabolism of pesticides in crops.

Rapid monitoring of fungicide fenhexamid residues in selected berries and wine grapes by square-wave voltammetry at carbon-based electrodes

A completely new electroanalytical method for the determination of fenhexamid (FNX) residues in fruit samples has been developed. This method is based on anodic oxidation of fungicide in Britton-Robinson buffer (pH 4) containing 10% (v/v) methanol using square-wave voltammetry when five different carbon-based electrodes were tested. An electrochemical behaviour of FNX was studied on a glassy carbon electrode using cyclic voltammetry, while glassy carbon paste electrode was selected for analytical purposes. Linear range for FNX from 3.96 to 49.50 µmol L^-1 characterized by coefficient of determination of 0.9964, sensitivity of 0.176 µA L µmol^-1_, and detection limit of 1.32 µmol L^-1 were calculated. Results acquired from analyses of blueberries and wine grapes were compared to those obtained by a reference chromatographic method, and a satisfactory agreement has been reached. Finally, it seems that the present voltammetric approach could find its application in food quality control as screening assay.

Botrytis prunorum Associated to Vitis vinifera Blossom Blight in Chile

Table grapes are highly susceptible to Botrytis cinerea infections during the bloom period. After reaching the flower development stage, B. cinerea remains quiescent until berry ripening or gives rise to blossom blight under specific climate conditions. A research study was conducted on the Chilean Central Valley during the 2018-2019 growing season. Flowers of Vitis vinifera cv. Thompson Seedless were collected and B. cinerea was isolated together to a second and morphologically different species, characterized by white mycelium and low to no sporulation (11.4% of total isolates). Three randomly selected isolates within this population were genetically examined and identified as Botrytis prunorum based on a phylogenetic multilocus approach using partial regions of genes RPB2, HSP60, and G3PDH or NEP1 and NEP2. Pathogenicity tests showed that B. prunorum infects and causes wilting in healthy table grape flowers. B. prunorum isolates were able to infect Thompson Seedless berries, inducing lesions between 13.11 and 41.53% with respect to the lesion diameter generated by B. cinerea B05.10. The fungicide sensitivity was evaluated. The three genetically characterized isolates were sensitive to boscalid and to cyprodinil/fludioxonil mixture with a mean EC₅₀ value of 5.5 µg/ml and 0.065 µg/ml, respectively. However, loss of sensitivity to fenhexamid was determined, with a mean EC₅₀ value of 5.13 µg/ml. Our understanding about blossom blight in V. vinifera has been limited to B. cinerea. Here we associated B. prunorum as a second causal agent of this disease in Chile. This data represents a first approach to the epidemiological characteristics of B. prunorum associated with blossom blight in table grapes.

Metabolism and Biological Activities of 4-Methyl-Sterols

4,4-Dimethylsterols and 4-methylsterols are sterol biosynthetic intermediates (C4-SBIs) acting as precursors of cholesterol, ergosterol, and phytosterols. Their accumulation caused by genetic lesions or biochemical inhibition causes severe cellular and developmental phenotypes in all organisms. Functional evidence supports their role as meiosis activators or as signaling molecules in mammals or plants. Oxygenated C4-SBIs like 4-carboxysterols act in major biological processes like auxin signaling in plants and immune system development in mammals. It is the purpose of this article to point out important milestones and significant advances in the understanding of the biogenesis and biological activities of C4-SBIs.

Transcriptome and Resistance-Related Genes Analysis of Botrytis cinerea B05.10 Strain to Different Selective Pressures of Cyprodinil and Fenhexamid

The pathogen Botrytis cinerea is a very dangerous pathogen that infects many economically important crops such as grape, strawberry, tomato, and eggplant. Cyprodinil, a pyrimidine amine fungicide, and fenhexamid, an amide fungicide, are new reagents for controlling gray mold with special efficacy. It is necessary to understand the change trends in the toxicological and physiological characteristics of B. cinerea with successive selective pressures of cyprodinil and fenhexamid to elongate the serving life of these fungicides for effective disease control. The toxicities of cyprodinil and fenhexamid at successive concentrations of EC25, EC50 and EC75 on B. cinerea strain BO5.10 were assayed along with mycelial growth-inhibition capacity. The results showed that the EC50 value of the cyprodinil-treated F27 strain increased approximately 18-fold, whereas of which in the fenhexamid-treated F27 strain increased only 3-fold compared with that of the F0 strain. The conductivities and glycerinum contents of the strains resistant to cyprodinil and fenhexamid were obviously enhanced; in contrast, the oxalic acid contents were decreased compared with those in the F0 strain. The transcriptomes of the F27 control (T01), cyprodinil-treated (T02) and fenhexamid- treated (T03) strains were analyzed, and the expression levels of functional genes in the T02 and T03 strains were significantly increased compared with those in the T01 strain; these results were further validated using qRT-PCR. The results indicated that the relative expression of two genes encoding mixed-functional oxidases (MFOs) BC1G_16062 and BC1G_16084, two genes encoding transmembrane proteins BC1G_12366 and BC1G_13768, two genes encoding Zinc finger proteins BC1G_13764 and BC1G_10483,one gene encoding citrate synthase enzyme BC1G_09151, one gene encoding gluconolactonase BC1G_15612 in the T02 and T03 strains and one gene encoding lysophospholipids enzyme BC1G_04893 in the T3 strain increased substantially compared with that in the T1 strain (P < 0.01). Functional prediction analysis of upregulated gene expression and structural verification was also performed, and the results showed that BC1G_10483 was a ZnF_C2HC transcriptional regulator interacting with the Sp1 element of these genes to respond to the pressures from cyprodinil and fenhexamid. Our results could contribute to a better understanding of the resistance mechanism of B. cinerea against cyprodinil and fenhexamid.

Elucidation of intermolecular interaction of bovine serum albumin with Fenhexamid: A biophysical prospect

Fenhexamid, as a hydroxyanilide, is widely applied to control Botrytis cinerea for protecting crops and fruits. But it could adversely affect human and animals health due to accumulation of residues in food production. Here, the affinity characteristics of fenhexamid on bovine serum albumin (BSA) was studied via a series of spectroscopic methods such as steady-state fluorescence spectroscopy, ultraviolet spectroscopy (UV), synchronous fluorescence spectroscopy (SFS), 3D fluorescence spectroscopy, and fourier transform infrared spectroscopy (FT-IR). The experimental results illustrated that the fluorescence quenching mechanism of BSA induced by fenhexamid was a static quenching. The binding constant (K_b) of fenhexamid with BSA was 2.399 × 10⁴ M^-1 at 298 K and the combination ratio was about 1:1. The competitive experiment demonstrated that fenhexamid was binding on the BSA at site II (subdomain IIIA), which was confirmed by the molecular docking studies. The negative values of thermodynamic parameter (ΔH⁰, ΔS⁰ and ΔG⁰) revealed that the reaction of fenhexamid with BSA could proceed spontaneously, the van der Waals force and hydrogen bonding interaction conducted the main effect, and the binding process was enthalpy-driven. What's more, the 8-Anilino-1-naphthalenesulfonate (ANS) and sucrose binding studies were also performed and further verified the binding force between BSA and fenhexamid.

Fludioxonil induced the cancer growth and metastasis via altering epithelial-mesenchymal transition via an estrogen receptor-dependent pathway in cellular and xenografted breast cancer models

Fludioxonil is an antifungal agent used in agricultural applications that is present at measurable amounts in fruits and vegetables. In this study, the effects of fludioxonil on cancer cell viability, epithelial-mesenchymal transition (EMT), and metastasis were examined in MCF-7 clonal variant breast cancer cell (MCF-7 CV cells) with estrogen receptors (ERs). MCF-7 CV cells were cultured with 0.1% DMSO (control), 17β-estradiol (E2; 1 ×10^-9 M, positive control), or fludioxonil (10^-5 -10^-8 M). MTT assay revealed that fludioxonil increased MCF-7 CV cell proliferation 1.2 to 1.5 times compared to the control, while E2 markedly increased the cell proliferation by about 3.5 times. When the samples were co-treated with ICI 182,780 (10^-8 M), an ER antagonist, fludioxonil-induced cell proliferation was reversed to the level of the control. Protein levels of cyclin E1, cyclin D1, Snail, and N-cadherin increased in response to fludioxonil as the reaction to E2, but these increases were not observed when fludioxonil was administered with ICI 182,780. Moreover, the protein level of p21 and E-cadherin decreased in response to treatment with fludioxonil, but remained at the control level when co-treated with ICI 182,780. In xenografted mouse models transplanted with MCF-7 CV cells, fludioxonil significantly increased the tumor mass formation by about 2.5 times as E2 did when compared to vehicle (0.1% DMSO) during the experimental period (80 days). Immunohistochemistry revealed that the protein level of proliferating cell nuclear antigen (PCNA), Snail, and cathepsin D increased in response to fludioxonil as the reaction to E2. These results imply that fludioxonil may have a potential to induce growth or metastatic behaviors of breast cancer by regulation of the expression of cell cycle-, EMT-, and metastasis-related genes via the ER-dependent pathway. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1439-1454, 2017.

A new transformant selection system for the gray mold fungus Botrytis cinerea based on the expression of fenhexamid-insensitive ERG27 variants

The gray mold fungus Botrytis cinerea features a wide host range and causes severe economic losses, making it an important object for molecular research. Thus far, genetic modification of the fungus mainly is relied on two selection systems (nourseothricin and hygromycin), while other selection systems hold significant disadvantages. To broaden the spectrum of available molecular tools, a new selection system based on the cheap and widely used fungicide fenhexamid (hydroxyanilide group) was established. Fenhexamid specifically targets the 3-ketoreductase ERG27 from the ergosterol biosynthesis pathway. We generated a set of expression vectors suitable for deletion or expression of genes of interest (GOIs) in B. cinerea based on fenhexamid-insensitive ERG27 variants. Expression of BcERG27^F412I and Fusarium fujikuroi ERG27 in the sensitive B. cinerea strain B05.10 causes resistance towards fenhexamid (fenR) and allows for the selection of transformants and their genetic purification. A modified split-marker approach facilitates the site-specific integration and expression of GOIs at the bcerg27 locus. No undesired secondary phenotypes regarding virulence, stress responses, the formation of reproductive structures or conidial germination were observed in strains expressing fenhexamid-insensitive ERG27 variants. Thus, the fenR system represents a third reliable selection system for genetic modifications of fenhexamid-sensitive B. cinerea strains.

Sensitivity of Phakopsora pachyrhizi Isolates to Fungicides and Reduction of Fungal Infection Based on Fungicide and Timing of Application

Soybean rust (SBR), caused by Phakopsora pachyrhizi, is a damaging foliar fungal disease in many soybean-growing areas of the world. Strategies to manage SBR include the use of foliar fungicides. Fungicide types, the rate of product application, and the number and timing of applications are critical components for successful rust management. The objectives of this study were to determine i) the sensitivity of P. pachyrhizi isolates collected in the U.S. to a range of fungicides and ii) the reduction of fungal infection based on fungicide type and timing of applications on soybean. There were differences (P < 0.05) in effective concentration (EC₅₀) values among the fungicides tested. Azoxystrobin had low EC₅₀ values for both urediniospore germination and fungal sporulation on inoculated leaflets. There were differences (P < 0.05) in fungal sporulation for application times, fungicide treatments, and their interaction when the fungus was inoculated on plants. All application times and nearly all fungicide treatments reduced (α = 0.05) fungal infection compared with the nonfungicide control. Information on fungicide sensitivity of P. pachyrhizi isolates and the preventive and curative effects of different fungicides are important in the management of SBR.

The natural fenhexamid-resistant grey mould populations from strawberry in Zhejiang Province are dominated by Botrytis cinerea group S

BACKGROUND

Recently, a novel clade Botrytis cinerea group S was found to be common in B. cinerea populations from Germany and New Zealand. Fenhexamid, an effective antibotrytis fungicide, has not been registered in China, but our preliminary study detected fenhexamid-resistant (HydR) isolates from strawberry in Zhejiang Province.

RESULTS

Genetic identification of 639 B. cinerea isolates from strawberry found that 331 (62.9%) belonged to B. cinerea group S. The frequency of HydR isolates ranged from 0 to 37.5% among the nine locations. Of the 74 HydR isolates, 71 were B. cinerea group S and moderately resistant to fenhexamid (HydR). Seven new mutations S9G, P57A, P269L, V365A, E368D, E375K and A378T in the target gene erg27 were reported for the first time. Sixty-two (83.8%) HydR isolates simultaneously carried P57A and A378T mutations, and further transformation assays showed that integration of one copy of erg27(P57A) (,) (A378T) into a wild-type strain led to partial resistance. Detached fruit studies showed that fenhexamid at the recommended field rate could control the disease incited by moderately resistant isolates but not by highly resistant isolates.

CONCLUSION

B. cinerea group S isolates are widespread in all strawberry-growing locations in Zhejiang Province. The natural HydR populations from strawberry are dominated by B. cinerea group S. © 2015 Society of Chemical Industry.

Effect of fenhexamid and cyprodinil on the expression of cell cycle- and metastasis-related genes via an estrogen receptor-dependent pathway in cellular and xenografted ovarian cancer models

Fenhexamid and cyprodinil are antifungal agents (pesticides) used for agriculture, and are present at measurable amounts in fruits and vegetables. In the current study, the effects of fenhexamid and cyprodinil on cancer cell proliferation and metastasis were examined. Additionally, the protein expression levels of cyclin D1 and cyclin E as well as cathepsin D were analyzed in BG-1 ovarian cancer cells that express estrogen receptors (ERs). The cells were cultured with 0.1% dimethyl sulfoxide (DMSO; control), 17β-estradiol (E2; 10(-9)M), and fenhexamid or cyprodinil (10(-5)-10(-7)M). Results of a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay showed that fenhexamid and cyprodinil increased BG-1 cell proliferation about 1.5 to 2 times similar to E2 (5 times) compared to the control. When the cells were co-treated with ICI 182,780 (10(-8)M), an ER antagonist, the proliferation of pesticide-treated BG-1 cells was decreased to the level of the control. A wound healing assay revealed that the pesticides reduced the disrupted area in the BG-1 cell monolayer similar to E2. Protein levels of cyclin D1 and E as well as cathepsin D were increased by fenhexamid and cyprodinil. This effect was reversed by co-treatment with ICI 182,780. In a xenograft mouse model with transplanted BG-1 cells, cyprodinil significantly increased tumor mass formation about 2 times as did E2 (6 times) compared to the vehicle (0.1% DMSO) over an 80-day period. In contrast, fenhexamid did not promote ovarian tumor formation in this mouse model. Cyprodinil also induced cell proliferation along with the expression of proliferating cell nuclear antigen (PCNA) and cathepsin D in tumor tissues similar to E2. Taken together, these results imply that fenhexamid and cyprodinil may have disruptive effects on ER-expressing cancer by altering the cell cycle- and metastasis-related gene expression via an ER-dependent pathway.

Toxicity evaluation of new agricultural fungicides in primary cultured cortical neurons

Fungicides are crucial for food protection as well as for the production of crops of suitable quality and quantity to provide a viable economic return. Like other pesticides, fungicides are widely sprayed on agricultural land, especially in wine-growing areas, from where they can move-off after application. Furthermore, residues of these agrochemicals can remain on crops after harvest and even after some food processing operations, being a major exposure pathway. Although a relatively low toxicity has been claimed for this kind of compounds, information about their neurotoxicity is still scarce. In the present study, nine fungicides recently approved for agricultural uses in the EU - ametoctradin, boscalid, cyazofamid, dimethomorph, fenhexamid, kresoxim-methyl, mepanipyrim, metrafenone and pyraclostrobin - have been evaluated for their toxicity in primary cultured mouse cortical neurons. Exposure to 0.1-100µM for 7 days in vitro resulted in a dose-dependent toxicity in the MTT cell viability assay. Strobilurin fungicides kresoxim-methyl (KR) and pyraclostrobin (PY) were the most neurotoxic compounds (lethal concentration 50 were in the low micromolar and nanomolar levels, respectively) causing a rapid raise in intracellular calcium [Ca(2+)]i and strong depolarization of mitochondrial membrane potential. KR- and PY-induced cell death was reversed by the calcium channels blockers MK-801 and verapamil, suggesting that calcium entry through NMDA receptors and voltage-operated calcium channels are involved in KR- and PY-induced neurotoxicity. These results highlight the need for further evaluation of their neurotoxic effects in vivo.

French vineyards provide information that opens ways for effective resistance management of Botrytis cinerea (grey mould)

Resistance to fungicides is an evolutionary process resulting from the selection of advantageous genotypes in naturally diverse populations. Seven fungicide modes of action are authorised to control grey mould caused by Botrytis cinerea on grapevine in France, and five of them have encountered specific resistance, with variable frequencies in populations and possible consequences for field fungicide efficacy. Moreover, multidrug resistance is caused by fungicide efflux and allows a weak resistance towards six unrelated modes of action. Here, a review is given of the fungicide resistance status of B. cinerea in France, particularly in the vineyards of Champagne, which are the most affected. Recently developed resistance and recent findings concerning the associated resistance mechanisms are focused upon in particular. Finally, antiresistance strategies are presented, and examples of managed resistance are discussed in a more general manner with the aim of extending this knowledge to other crops and countries undergoing similar resistance problems.

Role of sterol 3-ketoreductase sensitivity in susceptibility to the fungicide fenhexamid in Botrytis cinerea and other phytopathogenic fungi

BACKGROUND

The narrow-spectrum fungicide fenhexamid was introduced into French vineyards in 2000 to control grey mould caused by a complex of two cryptic species: Botrytis cinerea, the predominant species sensitive to fenhexamid, and Botrytis pseudocinerea, naturally resistant. Fenhexamid was suggested to inhibit the 3-ketoreductase involved at C-4 demethylation steps during ergosterol biosynthesis, as revealed by its effects on the B. cinerea sterol profile. Resistance monitoring studies have hitherto identified two B. cinerea fenhexamid-resistant phenotypes, both resulting from mutations in the erg27 gene encoding 3-ketoreductase.

RESULTS

The role of 3-ketoreductase sensitivity in fungal susceptibility to fenhexamid was investigated by studying sterol profiles and microsomal 3-ketoreductase in various fungal strains. Fenhexamid does inhibit B. cinerea 3-ketoreductase activity. Erg27 mutations causing amino acid substitutions in or near the transmembrane domain strongly decrease the affinity of fenhexamid for 3-ketoreductase. Fenhexamid has very low affinities for 3-ketoreductase in inherently resistant species, whether closely related to B. cinerea, like B. pseudocinerea, or more distantly related, like Nectria haematococca.

CONCLUSION

erg27 mutation and erg27 polymorphism may therefore contribute to the unfavourable binding of fenhexamid to its target, 3-ketoreductase, explaining the acquisition of fenhexamid resistance in B. cinerea and the narrow spectrum of this fungicide.

Phenotypic Characterization of Multifungicide Resistance in Botrytis cinerea Isolates from Strawberry Fields in Florida

Chemical control has always been essential for the management of gray mold, caused by Botrytis cinerea, to ensure sustainable strawberry production. However, lack of knowledge about actual resistance development may have disastrous consequences and lead to severe epidemics such as the one that affected several strawberry fields in 2012 in Florida. In this study, we tested 392 isolates collected from Florida strawberry fields between 2010 and 2012 for their sensitivity to boscalid (Bosc), a succinate dehydrogenase inhibitor (SdhI); pyraclostrobin, a quinone outside inhibitor (QoI); boscalid + pyraclostrobin (Pristine); fenhexamid, a hydroxyanilide (Hyd); pyrimethanil and cyprodinil, anilinopyrimidines; fludioxonil, a phenylpyrrole; and fludioxonil + cyprodinil (Switch). The respective resistance frequencies for boscalid, pyraclostrobin, Pristine, fenhexamid, cyprodinil, and pyrimethanil were 85.4, 86.5, 86.0, 44.4, 52.7, and 59.5%. Overall, 17.8 and 19.8% of isolates showed reduced sensitivity to fludioxonil and Switch, respectively. All fungicides sprayed preventively on detached strawberry fruit failed to control isolates with high levels of resistance to each fungicide except for fludioxonil and Switch. Four phenotypes with multifungicide resistance (MFR) were detected in B. cinerea populations from Florida. Isolates resistant to one fungicide (FR1), two (MFR2), three (MFR3), and four (MFR4) fungicides from different chemical groups represented 5.9, 28.6, 41.8, and 23.7% of the total resistant population, respectively. The MFR3 isolates were predominant and contained two subpopulations, the Bosc-QoI-AP^R isolates (56.5%) and the Bosc-QoI-Hyd^R isolates (40.6%). In addition to reporting on very highly resistant populations to boscalid and QoI fungicides, we show evidence for a widespread multifungicide resistance to B. cinerea that warrants immediate implementation of novel management strategies to impede the development of more resistant populations.

A functional bikaverin biosynthesis gene cluster in rare strains of Botrytis cinerea is positively controlled by VELVET

The gene cluster responsible for the biosynthesis of the red polyketidic pigment bikaverin has only been characterized in Fusarium ssp. so far. Recently, a highly homologous but incomplete and nonfunctional bikaverin cluster has been found in the genome of the unrelated phytopathogenic fungus Botrytis cinerea. In this study, we provided evidence that rare B. cinerea strains such as 1750 have a complete and functional cluster comprising the six genes orthologous to Fusarium fujikuroi ffbik1-ffbik6 and do produce bikaverin. Phylogenetic analysis confirmed that the whole cluster was acquired from Fusarium through a horizontal gene transfer (HGT). In the bikaverin-nonproducing strain B05.10, the genes encoding bikaverin biosynthesis enzymes are nonfunctional due to deleterious mutations (bcbik2-3) or missing (bcbik1) but interestingly, the genes encoding the regulatory proteins BcBIK4 and BcBIK5 do not harbor deleterious mutations which suggests that they may still be functional. Heterologous complementation of the F. fujikuroi Δffbik4 mutant confirmed that bcbik4 of strain B05.10 is indeed fully functional. Deletion of bcvel1 in the pink strain 1750 resulted in loss of bikaverin and overproduction of melanin indicating that the VELVET protein BcVEL1 regulates the biosynthesis of the two pigments in an opposite manner. Although strain 1750 itself expresses a truncated BcVEL1 protein (100 instead of 575 aa) that is nonfunctional with regard to sclerotia formation, virulence and oxalic acid formation, it is sufficient to regulate pigment biosynthesis (bikaverin and melanin) and fenhexamid HydR2 type of resistance. Finally, a genetic cross between strain 1750 and a bikaverin-nonproducing strain sensitive to fenhexamid revealed that the functional bikaverin cluster is genetically linked to the HydR2 locus.

Strong resistance to the fungicide fenhexamid entails a fitness cost in Botrytis cinerea, as shown by comparisons of isogenic strains

BACKGROUND

Fenhexamid, a sterol biosynthesis inhibitor effective against Botrytis, inhibits the 3-ketoreductase (Erg27) involved in C-4 demethylation. Several fenhexamid-resistant phenotypes have been detected in Botrytis cinerea populations from French vineyards. The field isolates with the highest resistance levels display amino acid changes in Erg27 (F412S, F412I or F412V).

RESULTS

Fenhexamid-resistant mutants were generated by site-directed mutagenesis of the erg27 gene in a sensitive recipient strain to overcome the impact of different genetic backgrounds. The wild-type erg27 allele was replaced by the three mutated alleles (erg27(F412S/I/V)) by homologous recombination. These isogenic strains were shown to be fenhexamid-resistant and were used to quantify the impact of F412 mutations on fungal fitness. Several parameters, including radial growth, the production of sclerotia and conidia, freezing resistance and aggressiveness, were quantified in laboratory conditions. Analysis of variance demonstrated significant differences between the mutant and parental strains for some characters. In particular, the mutants grew more slowly than the wild-type strain and displayed variations in the production of sclerotia and conidia with temperature and susceptibility to freezing.

CONCLUSIONS

The results highlight a moderate but significant impact of F412 mutations on the survival capacity of B. cinerea strains displaying high levels of resistance to fenhexamid in laboratory conditions, potentially limiting their dispersal and persistence, particularly in terms of overwintering, in field conditions.

Propiconazole inhibits the sterol 14α-demethylase in Glomus irregulare like in phytopathogenic fungi

The increasing concentrations impact (0.02, 0.2 and 2 mg L(-1)) of a Sterol Biosynthesis Inhibitor (SBI) fungicide, propiconazole, was evaluated on development and sterol metabolism of two non-target organisms: mycorrhizal or non-mycorrhizal transformed chicory roots and the arbuscular mycorrhizal fungus (AMF) Glomus irregulare using monoxenic cultures. In this work, we provide the first evidence of a direct impact of propiconazole on the AMF by disturbing its sterol metabolism. A significant decrease in end-products sterols contents (24-methylcholesterol and in 24-ethylcholesterol) was observed concomitantly to a 24-methylenedihydrolanosterol accumulation indicating the inhibition of a key enzyme in sterol biosynthesis pathway, the sterol 14α-demethylase like in phytopathogenic fungi. A decrease in end-product sterol contents in propiconazole-treated roots was also observed suggesting a slowing down of the sterol metabolism in plant. Taken together, our findings suggest that the inhibition of the both AM symbiotic partners development by propiconazole results from their sterol metabolism alterations.

Fungicide impacts on photosynthesis in crop plants

Fungicides are widely used to control pests in crop plants. However, it has been reported that these pesticides may have negative effects on crop physiology, especially on photosynthesis. An alteration in photosynthesis might lead to a reduction in photoassimilate production, resulting in a decrease in both growth and yield of crop plants. For example, a contact fungicide such as copper inhibits photosynthesis by destroying chloroplasts, affecting photosystem II activity and chlorophyll biosynthesis. Systemic fungicides such as benzimidazoles, anilides, and pyrimidine are also phytotoxic, whereas azoles stimulate photosynthesis. This article focuses on the available information about toxic effects of fungicides on photosynthesis in crop plants, highlighting the mechanisms of perturbation, interaction, and the target sites of different classes of fungicides.

The allele-specific probe and primer amplification assay, a new real-time PCR method for fine quantification of single-nucleotide polymorphisms in pooled DNA

The evolution of fungicide resistance within populations of plant pathogens must be monitored to develop management strategies. Such monitoring often is based on microbiological tests, such as microtiter plate assays. Molecular monitoring methods can be considered if the mutations responsible for resistance have been identified. Allele-specific real-time PCR approaches, such as amplification refractory mutation system (ARMS) PCR and mismatch amplification mutation assay (MAMA) PCR, are, despite their moderate efficacy, among the most precise methods for refining SNP quantification. We describe here a new real-time PCR method, the allele-specific probe and primer amplification assay (ASPPAA PCR). This method makes use of mixtures of allele-specific minor groove binder (MGB) TaqMan probes and allele-specific primers for the fine quantification of SNPs from a pool of DNA extracted from a mixture of conidia. It was developed for a single-nucleotide polymorphism (SNP) that is responsible for resistance to the sterol biosynthesis inhibitor fungicide fenhexamid, resulting in the replacement of the phenylalanine residue (encoded by the TTC codon) in position 412 of the enzymatic target (3-ketoreductase) by a serine (TCC), valine (GTC), or isoleucine (ATC) residue. The levels of nonspecific amplification with the ASPPAA PCR were reduced at least four times below the level of currently available allele-specific real-time PCR approaches due to strong allele specificity in amplification cycles, including two allele selectors. This new method can be used to quantify a complex quadriallelic SNP in a DNA pool with a false discovery rate of less than 1%.

Dissecting the sterol C-4 demethylation process in higher plants. From structures and genes to catalytic mechanism

Sterols become functional only after removal of the two methyl groups at C-4. This review focuses on the sterol C-4 demethylation process in higher plants. An intriguing aspect in the removal of the two C-4 methyl groups of sterol precursors in plants is that it does not occur consecutively as it does in yeast and animals, but is interrupted by several enzymatic steps. Each C-4 demethylation step involves the sequential participation of three individual enzymatic reactions including a sterol methyl oxidase (SMO), a 3β-hydroxysteroid-dehydrogenase/C4-decarboxylase (3βHSD/D) and a 3-ketosteroid reductase (SR). The distant location of the two C-4 demethylations in the sterol pathway requires distinct SMOs with respective substrate specificity. Combination of genetic and molecular enzymological approaches allowed a thorough identification and functional characterization of two distinct families of SMOs genes and two 3βHSD/D genes. For the latter, these studies provided the first molecularly and functionally characterized HSDs from a short chain dehydrogenase/reductase family in plants, and the first data on 3-D molecular interactions of an enzyme of the postoxidosqualene cyclase sterol biosynthetic pathway with its substrate in animals, yeast and higher plants. Characterization of these three new components involved in C-4 demethylation participates to the completion of the molecular inventory of sterol synthesis in higher plants.

Photochemical analysis of 14C-fenhexamid in aqueous solution and structural elucidation of a new metabolite

The photodegradation kinetics and the break down pathway of fenhexamid were studied in aqueous systems using [phenyl-UL-14C]- and [carbonyl-14C]-labelled compounds. The photolysis of fenhexamid followed first-order kinetics. The degradation rate of fenhexamid was significantly influenced by the solution pH with rate constants (k) of 2.11×10(-2), 4.47×10(-2), 6.11×10(-1) and 1.69 h(-1) at pH 5.0, 6.6, 7.3 and 9.0, respectively. Fenhexamid exhibited no significant change in degradation rate in the presence of acetone and hydrogen peroxide, while humic and fulvic acids retarded the degradation rate, because they shielded the active molecules from light. However, in phosphate medium, the photolysis rate was significantly enhanced as a function of concentration. About 3-8% and 10-25% photo mineralization were observed, using [carbonyl-14C]- and [phenyl-UL-14C]-labelled fenhexamid in aqueous solutions at different pH, respectively. In addition to four known metabolites, one major and five minor photoproducts out of which one is reported for the first time, were identified using high resolution LC-MS/MS and NMR. The toxicity of the new metabolite was tested against the fish Oncorhynchus mykiss with no lethal effect at 100 mg L(-1).

Monoclonal antibody generation and direct competitive enzyme-linked immunosorbent assay evaluation for the analysis of the fungicide fenhexamid in must and wine

Fenhexamid is a common fungicide used to fight botrytis infections in a great variety of plant crops, particularly in vineyards. In this study, high-affinity and specific monoclonal antibodies against fenhexamid were produced for the first time, and an enzyme-linked immunosorbent assay (ELISA) in the antibody-coated direct competitive format was developed. The derivative 4-[2,3-dichloro-4-(1-methylcyclohexanecarboxamido)phenoxy]butanoic acid, with a carboxylic spacer arm attached to the phenolic hydroxyl group of fenhexamid, was synthesized for antibody production and ELISA development. To optimize this assay, the dependence of assay parameters on ionic strength and pH was assessed, and the influence of several organic solvents was determined. The IC(50) value of the optimized assay for fenhexamid and the calculated limit of detection in phosphate buffer were 0.52 +/- 0.06 and 0.13 +/- 0.03 microg/L, respectively. Preliminary studies using fortified must and wine samples indicated that the presence of fenhexamid below the maximum residue limits in grapes could be easily determined with the developed immunoassay by a simple dilution of the sample in water.

Effectiveness of control strategies against Botrytis cinerea in vineyard and evaluation of the residual fungicide concentrations

This investigation was undertaken to test different control strategies against Botrytis cinerea vineyards. Two commercial vineyards, "Barbera" and "Moscato," located in Piedmont (Northern Italy) were divided into seven plots and treated with different combinations of fungicides including fenhexamid, pyrimethanil, fludioxonil + cyprodinil, iprodione, and boscalid, a new carboxamide compound. An integrated strategy including a chemical (pyrimethanil) and a biocontrol agent (Trichoderma spp. t2/4ph1) was also included. At harvest, the percentage of bunches and berries attacked by B. cinerea and the concentration of the chemical fungicides were determined. All the pesticide residues at harvest were below the maximum residue level (MRL), except when two applications of pyrimethanil per season were applied. Boscalid was the most effective active ingredient against B. cinerea among the tested chemicals. When boscalid application was followed by a treatment with pyrimethanil, its efficacy was similar to that shown by two treatments of pyrimethanil. However, this second strategy was not feasible due to the risks of resistance development in the pathogen and to the residue accumulation as indicated by the analysis.

Botryticides affect grapevine leaf photosynthesis without inducing defense mechanisms

The effects of the two botryticides, fludioxonil (fdx) and fenhexamid (fhd), were investigated on grapevine leaves (Vitis vinifera L. cv. Pinot noir) following photosynthesis and defense mechanisms. Treatments were carried out in vineyard at the end of flowering. Phytotoxicity of both fungicides was evaluated by measuring variations of leaf photosynthetic parameters and correlated expression of photosynthesis-related genes. Results demonstrated that similar decrease in photosynthesis was caused by fdx and fhd applications. Moreover, the mechanism leading to photosynthesis alteration seems to be the same for both fungicides. Stomatal limitation to photosynthetic gas exchange did not change following treatments indicating that inhibition of photosynthesis was mostly attributed to non-stomatal factors. Nevertheless, fungicides-induced depression of photosynthesis was related neither to a decrease in Rubisco carboxylation efficiency and in the capacity for regeneration of ribulose 1,5-bisphosphate nor to loss in PSII activity. However, fdx and fhd treatments generated repression of genes encoding proteins involved in the photosynthetic process. Indeed, decreased photosynthesis was coupled with repression of PsbP subunit of photosystem II (psbP1), chlorophyll a/b binding protein of photosystem I (cab) and Rubisco small subunit (rbcS) genes. A repression of these genes may participate in the photosynthesis alteration. To our knowledge, this is the first study of photosynthesis-related gene expression following fungicide stress. In the meantime, defense responses were followed by measuring chitinase activity and expression of varied defense-related genes encoding proteins involved in phenylpropanoid synthesis (PAL) or octadecanoid synthesis (LOX), as well as pathogenesis-related protein (Chi4C). No induction of defense was observed in botryticides-treated leaves. To conclude, the photosynthesis is affected without any triggering of plant defense responses.

Toxicity of six novel fungicides and sulphur to Galendromus occidentalis (Acari: Phytoseiidae)

A laboratory evaluation of fenbuconazole, myclobutanil propiconazole, boscalid, fenhexamid and pyraclostrobin revealed these fungicides to be harmless to adult Galendromus occidentalis. None of these fungicides affected adversely fecundity and egg viability. Elemental sulphur also had no effect on adults and fecundity. However, 72.4% of the young larvae perished after hatching. The six novel fungicides are safer alternatives to sulphur in perennial crops in British Columbia.

Genetic analysis of fenhexamid-resistant field isolates of the phytopathogenic fungus Botrytis cinerea

The hydroxyanilide fenhexamid, one of the latest antibotrytis fungicides, active especially against leotiomycete plant-pathogenic fungi, inhibits 3-ketoreductase of the C-4-demethylation enzyme complex during ergosterol biosynthesis. We isolated Botrytis cinerea strains resistant to various levels of fenhexamid from French and German vineyards. The sequence of the gene encoding 3-ketoreductase, erg27, varied according to levels of resistance. Highly resistant isolates, termed HydR3(+), all presented a modification of the phenylalanine at the C terminus of the putative transmembrane domain at position 412, either to serine (85% of the isolates), to isoleucine (11.5% of the isolates), or to valine (3.5% of the isolates). The introduction of the erg27(HydR3(+)) allele into a fenhexamid-sensitive strain by means of a replicative plasmid conferred fenhexamid resistance on the resulting transformants, showing that the mutations at position 412 are responsible for fenhexamid resistance. Weakly to moderately resistant isolates, termed HydR3(-), showed different point mutations between the strains in the sequenced regions of the erg27 gene, corresponding to amino acid changes between positions 195 and 400 of the protein. The erg27(HydR3(-)) alleles on the replicative vector introduced into a sensitive strain did not confer resistance to fenhexamid. Genetic crosses between HydR3(-) and sensitive strains showed strict correlation between the sequenced mutation in the erg27 gene and the resistance phenotypes, suggesting that these mutations are linked to fenhexamid resistance. The HydR3 mutations possibly modify the affinity of the 3-ketoreductase enzyme for its specific inhibitor, fenhexamid.

A Botrytis cinerea emopamil binding domain protein, required for full virulence, belongs to a eukaryotic superfamily which has expanded in euascomycetes

A previous transcriptomic analysis of 3,032 fungal genes identified the Botrytis cinerea PIE3 (BcPIE3) gene to be up-regulated early in planta (A. Gioti, A. Simon, P. Le Pêcheur, C. Giraud, J. M. Pradier, M. Viaud, and C. Levis, J. Mol. Biol. 358:372-386, 2006). In the present study, BcPIE3 was disrupted in order to determine its implication in pathogenicity. BcPIE3 was shown to be a virulence factor, since the DeltaBcPIE3 mutant was blocked during the colonization of tomato and bean leaves, giving lesions reduced in size by at least 74%. Within the emopamil binding domain (EBD), BcPIE3 shows significant structural similarities to mammalian emopamil binding proteins (EBPs). Mammalian EBPs function as sterol isomerases, but an analysis of the sterol content and the results of growth inhibition experiments with the DeltaBcPIE3 strain indicated that BcPIE3 is dispensable for ergosterol biosynthesis. The systematic identification of EBD-containing proteins included in public databases showed that these proteins constitute a protein superfamily present only in eukaryotes. Phylogenetic analysis showed that the ancestral EBD-encoding gene was duplicated in the common ancestor of animals and fungi after the split from plants. Finally, we present evidence that the EBP phylogenetic clade of this superfamily has further expanded exclusively in euascomycetes, especially in B. cinerea, which contains three copies of the EBP gene.

Resistance of Botrytis cinerea Isolates from Vegetable Crops to Anilinopyrimidine, Phenylpyrrole, Hydroxyanilide, Benzimidazole, and Dicarboximide Fungicides

During February 2005, 55 single-spore isolates of Botrytis cinerea were collected at the end of the season from vegetable crops grown in 18 greenhouses on the island of Crete, Greece. They were tested for sensitivity to the anilinopyrimidine fungicides pyrimethanil and cyprodinil, the hydroxyanilide fungicide fenhexamid, the phenylpyrrole fungicide fludioxonil, the dicarboximide fungicide iprodione, and the benzimidazole fungicide carbendazim. Results of the study showed the existence of benzimidazole- and dicarboximide-resistant strains at frequencies of 61.8 and 18%, respectively. Moreover, for first time, the development of resistance to anilinopyrimidine fungicides by B. cinerea was detected in greenhouse vegetable crops on the island of Crete. High resistance frequencies of 49.1 and 57.4% were observed for pyrimethanil and cyprodinil, respectively. In addition, one isolate was found to be resistant to the hydroxyanilide fungicide fenhexamid, while no strains resistant to the phenylpyrrole fungicide were detected. Among the 55 isolates tested, 13 were resistant only to carbendazim, 6 were resistant only to anilinopyrimidines, 3 were resistant to both benzimidazoles and dicarboximides, 17 were resistant to both benzimidazoles and anilinopyrimidines, 6 were resistant to both dicarboximides and anilinopyrimidines, 1 was simultaneously resistant to benzimidazoles, dicarboximides, and anilinopyrimidines, 1 was resistant to both anilinopyrimidines and hydroxyanilides, and 8 were sensitive to all fungicides tested. A strong cross-resistance relationship was found between the two anilinopyrimidine fungicides tested when log transformed EC₅₀ values of the isolates were subjected to a linear regression analysis (r = 0.71). Despite the detection of several phenotypes with simultaneous resistance to chemically unrelated active ingredients, in none of the remaining possible fungicide pairs was there observed any kind of cross-resistance relationship.

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.

Biogenesis, molecular regulation and function of plant isoprenoids

Isoprenoids represent the oldest class of known low molecular-mass natural products synthesized by plants. Their biogenesis in plastids, mitochondria and the endoplasmic reticulum-cytosol proceed invariably from the C5 building blocks, isopentenyl diphosphate and/or dimethylallyl diphosphate according to complex and reiterated mechanisms. Compounds derived from the pathway exhibit a diverse spectrum of biological functions. This review centers on advances obtained in the field based on combined use of biochemical, molecular biology and genetic approaches. The function and evolutionary implications of this metabolism are discussed in relation with seminal informations gathered from distantly but related organisms.