Postinfection Application of Fenhexamid at Lower Doses in Conjunction with Captan Slowed Fungicide Resistance Selection in Botrytis cinerea on Detached Grape Berries.

Fungicide resistance is a limiting factor in sustainable crop production. General resistance management strategies such as rotation and mixtures of fungicides with different modes of action have been proven to be effective in many studies, but guidance on fungicide dose or application timing for resistance management remains unclear or debatable. In this study, Botrytis cinerea and the high-risk fungicide fenhexamid were used to determine the effects of fungicide dose, mixing partner, and application timing on resistance selection across varied frequencies of resistance via detached fruit assays. The results were largely consistent with the recent modeling studies that favored the use of the lowest effective fungicide dose for improved resistance management. In addition, even 10% resistant B. cinerea in the population led to about a 40% reduction of fenhexamid efficacy. Overall, our findings show that application of doses less than the fungicide label dose, mixture with the low-risk fungicide captan, and application postinfection seem to be the most effective management strategies in our controlled experimental settings. This somewhat contradicts the previous assumption that preventative sprays help resistance management.

Induction of Systemic Resistance in Chickpea (Cicer arietinum L.) Against Fusarium oxysporum f. sp. ciceris by Antagonistic Rhizobacteria in Assistance with Native Mesorhizobium.

In the present study five potent rhizobacterial antagonists of Fusarium oxysporum f. sp. ciceris alone and in combination with Mesorhizobium (M) were evaluated for their potential to elicit the defence response reactions to reduce the total loss of plants and enhance the growth of two chickpea cultivars i.e. resistant GPF-2 and susceptible JG-41. Observations revealed that maximum phenolic, peroxidase (PO) and polyphenol oxidase (PPO) activity was induced after 30th day of germination. Maximum phenol concentration of 745.8 and 724.1 µg/gfw root tissues was recorded by Ps45 when co-inoculated with Mesorhizobium in both the varieties i.e. GPF-2 and JG-41 respectively. Isolates Ps45, Ps47 and Ps44 were found most promising to induce PO and PPO activity, in combination with Mesorhizobium and recorded superior over the fungicide with respect to negative control. Similar results were recorded for the phenylalanine ammonia lyase (PAL), maximally induced on 20th day after germination, where dual inoculation of Ps44+M and Ps45+M induced 57.0 and 54.2 nmol of cinnamic acid min-1 gfw-1 in GPF-2. However in case of JG-41, Ps45 and Ba1a exhibited highest PAL activity of 54.2 and 41.4 nmol of cinnamic acid min-1 gfw-1. Malonic aldehyde concentration in stem tissues at 30th day revealed that lipid peroxidation was effectively reduced in rhizobacterial treated plants compared to fungicide and negative control, signifying the role of antagonistic plant growth promoting rhizobacteria in reducing the stress and enhancing the plant's defence response to reduce the disease incidence and thus improving the plant growth and yield. Moreover the dual inoculations were observed superior over the fungicide treatment as well as single inoculations in terms of growth (root/shoot length and weight), signifying the synergistic effect of screened antagonists and native Mesorhizobium in suppressing the pathogen and thereby enhancing the plant growth.

Seed mucilage interacts with soil microbial community and physiochemical processes to affect seedling emergence on desert sand dunes.

Seedling emergence is a critical stage in the establishment of desert plants. Soil microbes participate in plant growth and development, but information is lacking with regard to the role of microbes on seedling emergence. We applied the biocides (captan and streptomycin) to assess how seed mucilage interacts with soil microbial community and physiochemical processes to affect seedling emergence of Artemisia sphaerocephala on the desert sand dune. Fungal and bacterial community composition and diversity and fungal-bacterial interactions were changed by both captan and streptomycin. Mucilage increased soil enzyme activities and fungal-bacterial interactions. Highest seedling emergence occurred under streptomycin and mucilage treatment. Members of the phyla Firmicutes and Glomeromycota were the keystone species that improved A. sphaerocephala seedling emergence, by increasing resistance of young seedlings to drought and pathogen. Seed mucilage directly improved seedling emergence and indirectly interacted with the soil microbial community through strengthening fungal-bacterial interactions and providing favourable environment for soil enzymes to affect seedling emergence. Our study provides a comprehensive understanding of the regulatory mechanisms by which soil microbial community and seed mucilage interactively promote successful establishment of populations of desert plants on the barren and stressful sand dune.

Antifungal activity of the essential oils of some medicinal plants against human and plant fungal pathogens.

The present study was conducted to assess the antifungal activity of essential oils of medicinal plants Mentha piperita (peppermint), Foeniculum vulgare, Satureja hortensis (Savory), Ferula asafoetida and Cuminum cyminum against Alternaria sp., Bipolaris sorokiniana and Acremonium sclerotigenum. The antifungal activity was evaluated by Broth Microdilution Method. Minimum Inhibitory Concentration (MICs) and Minimum Fungicidal Concentration (MFCs) of the essential oils were compared with Amphotricin B and Captan as standard drug. MIC values for all essential oils were between 1 to 8 mg/mL. MIC value of Fennel essential oil was comparable to MFC value obtained from fungicide Captan. Peppermint essential oil exhibited maximum inhibitory and fungicide activity in concentrations of 2 mg/ml and 4 mg/ml against Alternaria sp. The essential oil was more effective than Fennel against Bipolaris, but MFC values of both essential oils were 4 mg/ml. C. cyminum displayed less susceptibility against all of the fungi. Regarding our finding, peppermint and Fennel oil seem to be a promising solution to control plant diseases.

Effects of Folpet, Captan, and Captafol on Human Aromatase in JEG-3 Cells.

BACKGROUND: Estradiol, produced by aromatase (CYP19A1), is very important for reproduction. Folpet, captan, and captafol belong to the phthalimide class of fungicides. They are used to protect the leaves of plants or fruits. They could be endocrine disruptors and may disrupt CYP19A1 activity. METHODS: In the present study, we investigated the effects of folpet, captan, and captafol on estradiol production and human CYP19A1 activity in JEG-3 cells. RESULTS: Folpet, captan, and captafol decreased estradiol production in JEG-3 cells in a concentration-dependent manner. Folpet, captan, and captafol inhibited human CYP19A1 with inhibitory concentration (IC50) values of 3.55, 10.68, and 1.14 µmol/L respectively. These chemicals competitively inhibited human CYP19A1. Molecular docking simulation analysis showed that they tended to bind to the steroid-binding pocket of the CYP19A1. However, the required concentrations may not be relevant to the negligible systemic exposures in humans to these chemicals. CONCLUSION: Folpet, captan, and captafol are potential inhibitors of human CYP19A1.

Screening and characterization of Xanthomonas oryzae pv. oryzae strains with resistance to pheazine-1-carboxylic acid.

Xanthomonas oryzae pv. oryzae (Xoo) causes bacterial leaf blight (BLB) and can be effectively controlled by phenazine-1-carboxylic acid (PCA), an antibiotic secreted by Pseudomonas spp. PCA resistance in Xoo was investigated in this research. Only four PCA-resistant strains were obtained by extensive screening, and the resistance was genetically stable in only one of them (P4). P4 was also resistant to phenazine and 1-hydroxyphezine but not to captan, bismerthiazol, or streptomycin. The following were reduced in P4 relative to the parental wild type: growth, virulence, EPS production, extracellular cellulase production and activity, biofilm formation, and swimming ability. ROS accumulation was reduced, resistance to exogenous H2O2 was increased, and expression of catalase genes and catalase activities were increased in P4, suggesting that PCA resistance in P4 results from a reduction in ROS production and/or an increased ability to metabolize ROS following PCA treatment. Given the low risk of Xoo developing PCA resistance and the reduced virulence and fitness of the resistant strain, PCA can be used in alternation with other common bactericides to control BLB in rice fields.

Incorporating Adjuvants with Captan to Manage Common Apple Diseases.

Captan has become an increasingly important fungicide in the management of common apple diseases such as apple scab (Venturia inaequalis) and bitter rot (Colletotrichum spp.) due to the low risk of fungicide resistance evolving in either pathogen population to this product. Restrictions on the amount of captan that can be applied per season limits the amount and the number of applications a grower may use, resulting in control failures during high disease pressure years. This 3-year field study evaluated how adjuvants combined with captan affected the incidence and severity of apple scab and bitter rot on two different apple cultivars. Results showed that Li700 plus captan and Bond Max plus captan reduced disease incidence of apple scab and bitter rot in years with moderate to high disease pressure by increasing the coverage and retention of captan. The addition of these adjuvants also resulted in possible yield losses due to russetting caused by phytotoxicity. The overall benefits of incorporating adjuvants with captan based on this study could reduce disease incidence while potentially saving a grower up to $5,329 ha-1 due to fungicide reduction.

Potential Impact of Populations Drift on Botrytis Occurrence and Resistance to Multi- and Single-Site Fungicides in Florida Southern Highbush Blueberry Fields.

Incidence of blossom blight and Botrytis fruit rot (BFR), caused by Botrytis cinerea, on two southern highbush blueberry cultivars was evaluated in several blueberry fields grown in the vicinity (BB-Str(+)) or not (BB-Str(-)) of strawberry fields in central Florida. Blossom blight and BFR incidence were higher in BB-Str(+) fields in 2014 and significantly higher in 2015 compared to BB-Str(-) fields. In total, 613 B. cinerea isolates (i.e., 181 and 432 isolates from BB-Str(-) and BB-Str(+) fields, respectively) were collected. The isolates were evaluated for sensitivity to eight single-site and one multisite fungicides using a spore germination and a germ tube elongation assay. Overall, 5, 15, 24, 28, 54, and 93% of isolates collected from BB-Str(-) were resistant to penthiopyrad, cyprodinil, boscalid, fenhexamid, pyraclostrobin, and thiophanate-methyl, respectively. Respective resistance frequencies in BB-Str(+) isolates were 10, 30, 65, 66, 89, and 99%. Resistance frequencies for all fungicides were always higher in BB-Str(+) fields compared to BB-Str(-) fields. Isolates exhibiting resistance to six or five fungicides simultaneously were predominant (50 to 70%) in blueberry fields regardless if they were grown in the vicinity of strawberry fields or not. Among 308 and 305 B. cinerea isolates tested in 2014 and 2015, 41.8 and 47.1%, respectively, showed reduced sensitivity to the multisite fungicide captan. The lower label rate of captan applied preventively did not control isolates with reduced sensitivity on detached blueberry fruit. These findings suggest a potential population flow between strawberry and blueberry fields that may impact blossom blight and gray mold development in blueberry fields. The relatively lower fungicide input applied to blueberry fields compared with strawberry fields seems to be sufficient to select for resistance and multiple-resistant phenotypes in B. cinerea populations in blueberry.

Necrotic and apoptotic cell death induced by Captan on Saccharomyces cerevisiae.

Captan is one of the most widely used broad-spectrum fungicide applied to control several early and late diseases of grapes, apples, and other fruits and vegetables, and as other phthalimide fungicides is defined as a multisite compound with thiol-reactivity. Captan can affect non-target organisms as yeasts, modifying microbial populations and fermentation processes. In this study, we asked whether Captan thiol-reactivity and other mechanisms are involved in acute Captan-induced cell death on aerobic growing Saccharomyces cerevisiae. Thus for, we analyze cellular protein and non-protein thiols, cell membrane integrity, reactive oxygen species accumulation, phosphatidylserine externalization, and apoptotic mutants behavior. The results showed that when submitted to acute Captan treatment most cells lost their membrane integrity and died by necrosis due to Captan reaction with thiols. However, part of the cells, even maintaining their membrane integrity, lost their culture ability. These cells showed an apoptotic behavior that may be the result of non-protein thiol depletion and consequent increase of reactive oxygen species (ROS). ROS accumulation triggers a metacaspase-dependent apoptotic cascade, as shown by the higher viability of the yca1-deleted mutant. Together, necrosis and apoptosis are responsible for the high mortality detected after acute Captan treatment of aerobically growing cells of S. cerevisiae.

Differential immunomodulatory effects of six pesticides of different chemical classes on human monocyte-derived macrophage functions.

Exposure to pesticides through eyes, skin, ingestion and inhalation may affects human health by interfering with immune cells, such as macrophages. We evaluated, in vitro, the effect of six pesticides widely used in apple arboriculture on the functions of human monocyte-derived macrophages (hMDMs). hMDMs were cultured for 4 or 24 h with or without pesticides (0.01, 0.1, 1, 10 µmol.L-1). We showed that chlorpyrifos, thiacloprid, thiophanate, boscalid, and captan had little toxic effect at the tested concentrations, while dithianon had low-cytotoxicity at 10 µmol.L-1. While boscalid showed no effect on hMDMs function, thiophanate (0.01 µmol.L-1) stimulated with TPA and thiacloprid (1, 10 µmol.L-1) stimulated with zymosan activated ROS production. Chlorpyrifos, dithianon, and captan inhibited ROS production and TNF-α, IL-1ß pro-inflammatory cytokines. We established that dithianon (0.01-1 µmol.L-1) and captan (0.1, 1 µmol.L-1) induced mRNA expression of NQO1 and HMOX1 antioxidant enzymes. Dithianon also induced the mRNA expression of catalase, superoxide dismutase-2 at 10 µmol.L-1. Together, these results show that exposure to chlorpyrifos, dithianon, and captan induce immunomodulatory effects that may influence the disease fighting properties of monocytes/macrophages while pesticides such as thiacloprid, thiophanate and boscalid have little influence.

Triple-Smart Eco-Friendly Chili Anthracnose Control Agro-Nanocarrier.

Pesticide leaching and soil contamination are major issues in the present agriculture formulations. Hence, here 2D graphene oxide in combination with cationic, anionic, or nonionic polymers were tested for runoff resistance and targeted release behavior. Cationic polymer supplemented the binding of rGO on leaf surface by 30% more than control and reduced off-target leaching in soil by 45% more than control. Further, to enhance the fruit rot control caused by Colletotrichum capsici in chili crop, the rGO was decorated with Cu2-xSe nanocrystals, which provided combined disease control with captan. The chitosan coating in the nanocomposite added targeted pH-responsive fungal inhibition behavior and could reduce the C. capsici growth by ∼1/2 times compared to captan control.

Contrasting short-term antibiotic effects on respiration and bacterial growth compromises the validity of the selective respiratory inhibition technique to distinguish fungi and bacteria.

The selective inhibition (SI) technique has been widely used to resolve fungal and bacterial biomass. By studying bacterial growth (leucine/thymidine incorporation) and respiration simultaneously, this study demonstrates that the inhibitors the SI technique is based on do not efficiently or specifically resolve fungal and bacterial contributions to respiration. At concentrations that completely inhibited bacterial growth, the bactericide streptomycin had no influence on the SI technique's respiration measurement, and complete inhibition of bacterial growth using oxytetracycline resulted in marginal respiration reductions. The fungicides captan and benomyl severely inhibited non-target bacterial growth. Cycloheximide did not reduce bacterial growth at moderate concentrations, but the cycloheximide respiration reduction was no higher in a soil with more fungal biomass, casting doubt on its ability to discriminate fungal respiration contribution. Conclusions regarding bacteria and fungi based on the SI technique using these inhibitors are thus compromised. The inhibition of glucose-activated respiration by the bactericide bronopol appeared to correlate with bacterial growth inhibition, however. Bronopol, combined with growth-based techniques, could aid development of a new framework to resolve decomposer ecology in soil.

Effects of captan on Apis mellifera brood development under field conditions in California almond orchards.

Three almond field trials were conducted during 2003 and 2004 at two locations in central (Fresno County) and northern (Yolo County) California to evaluate the potential effects of commercial applications of Captan on honey bees, Apis mellifera L. Captan was applied at 5.0 kg (AI)/ha during bloom. Hives were evaluated for hive health and brood development parameters for approximately 2 mo after application. This study showed that the application of Captan was not harmful to foraging honey bees or their brood. No treatment-related effects were noted on hive weights, dead bee deformity, number of dead bees, survival of individual larvae, weight of individual emerging adults, and other hive health parameters.

Antinociceptive effects of tetrahydrophthalimides and related compounds.

This paper describes the antinociceptive effects of tetrahydrophthalimides and related compounds in mice. Twenty compounds were obtained by the reaction of cis-1,2,3,6-tetrahydrophthalic anhydride with appropriate amines, dehydration, and addition to the imidic double bond. They were analyzed in the writhing test at 10 mg/kg given intraperitoneally. The most active compound 2-benzyl-5-morpholin-4-yl-hexahydroisoindole-1,3-dione (19) was studied on formalin, capsaicin, glutamate and hot plate models. The antinociceptive activity demonstrated by some studied compounds is promising, and some of them were more active than acetylsalicylic acid and paracetamol used as reference drugs in writhing tests in mice. Compound 19 was about 5-fold more potent than the reference drugs, being also effective by oral route and against the inflammatory response in the formalin test. The results suggest that compound 19 could be used as a model to obtain new and more potent antinociceptive agents. It exhibits an interesting antinociceptive profile, and does not interact with opioid systems.

Why Can Unnatural Electron Acceptors Protect Photosynthesizing Organisms but Kill the Others?

The polychlorinated compounds captafol (CPL) and 2,6-dichloroisonicotinic acid (INA) are able to protect plants acting as a fungicide or an inductor of plant resistance, respectively. At the same time, CPL and INA are dangerous for the respiratory organisms, i.e. mammalians, bacteria, and fungi. The high electron-withdrawing ability of these compounds enables them to serve as unnatural electron acceptors in the cellular ambient near to electron transport pathways located in the thylakoid membrane of chloroplasts or in the mitochondrial respiratory chain. Low-energy electron attachment to CPL and INA in vacuo leads to formation of many fragment species mainly at thermal electron energy as it is shown using dissociative electron attachment spectroscopy. On the basis of the experimental findings, assigned with the support of density functional theory calculations it is suggested that the different bioactivity of CPL and INA in respiratory and photosynthetic organisms is due to the interplay between the dissociative electron attachment process and the energies of electrons leaked from the electron transport pathways.

Alteration of the exonuclease activities of DNA polymerase I by captan.

DNA polymerase I is a multifaceted enzyme with one polymerizing and two exonuclease activities. Captan was previously shown to be an inhibitor of this enzyme's polymerizing activity and this report measures the effects of captan on the two exonuclease activities. When the holoenzyme was tested, captan enhanced the degradation of poly(dA-dT), T7 DNA and, to a significantly lesser extent, heat-denatured DNA. However, when the effects of captan were tested as a function of substrate concentration, the stimulatory influence was measured only at high substrate concentrations. At low concentrations of DNA, captan was inhibitory. Inhibition and enhancement each showed an ED50 of the same value (approx. 100 microM). By assaying the two exonuclease activities separately it was shown that the differential effect on the holoenzyme by captan was the result of a combined inhibition of the 3'----5' exonuclease and enhancement of the 5'----3' exonuclease. Klenow fragment with poly(dA-dT) as substrate was used to assay for 3'----5' exonuclease activity. Captan inhibited this exonuclease and the inhibition could be prevented by the addition of greater concentrations of substrate. Holoenzyme and poly(rA)-poly(dT) were used to assay for 5'----3' exonucleolysis, which was enhanced at higher concentrations of substrate in the presence of captan.

Inhibition of DNA polymerase by captan.

Captan inhibits DNA polymerases of both eukaryotic and prokaryotic sources. When polymerases were employed in assays with various nucleotides as template-primer, no specificity in the base sequence of polynucleotide was required for inhibition. Sucrose gradient centrifugation and preincubation studies showed the inhibition was caused by an irreversible alteration of the polymerase. Captan and DNA compete for the same site on the polymerase, thus DNA can serve a protective role in the elimination of captan's action. The pyrophosphate exchange activity associated with the polymerase is not inhibited by captan and the fidelity with which DNa polymerase I copies the DNA template also is not altered by captan treatment.

Interaction of glutathione transferase P1-1 with captan and captafol.

Glutathione transferase (GST, EC 2.5.1.18) P1-1 was strongly inhibited by captan and captafol in a time- and concentration-dependent manner. The IC50 values for captan and captafol were 5.8 microM and 1.5 microM, respectively. Time-course inactivation of GSTP1-1 by two pesticides was prevented by 3 microM of hexyl-glutathione, but not by methylglutathione. The fact that the inactivated enzyme recovered all the 5,5'-dithiobis(2-nitrobenzoic acid) titrable thiol groups, with concomitant recovery of all its original activity after treatment with 100 microM dithiothreitol, suggested that captan and captafol were able to induce the formation of disulfide bonds. That the inactivation of GSTP1-1 by captan and captafol involves the formation of disulfide bonds between the four cysteinil groups of the enzymes was confirmed by the SDS-PAGE experiments on nondenaturant conditions. In fact, on SDS-PAGE, GSTP1-1 as well as the cys47ala, cys101ala, and cys47ala/cys101ala GSTP1-1 mutants treated with captan and captafol showed several extra bands, with apparent molecular masses higher and lower than the molecular mass of native GSTP1-1 (23.5 kDa), indicating that both intra- and inter-subunit disulfide bonds were formed. These extra bands returned to the native 23.5 kDa band with concomitant restoration of activity when treated with dithiothreitol.

Inhibition of RNA polymerase by captan at both DNA and substrate binding sites.

RNA synthesis carried out in vitro by Escherichia coli RNA polymerase was inhibited irreversibly by captan when T7 DNA was used as template. An earlier report and this one show that captan blocks the DNA binding site on the enzyme. Herein, it is also revealed that captan acts at the nucleoside triphosphate (NTP) binding site, and kinetic relationships of the action of captan at the two sites are detailed. The inhibition by captan via the DNA binding site of the enzyme was confirmed by kinetic studies and it was further shown that [14C]captan bound to the beta' subunit of RNA polymerase. This subunit contains the DNA binding site. Competitive-like inhibition by captan versus UTP led to the conclusion that captan also blocked the NTP binding site. In support of this conclusion, [14C]captan was observed to bind to the beta subunit which contains the NTP binding site. Whereas, preincubation of RNA polymerase with both DNA and NTPs prevented captan inhibition, preincubation with either DNA or NTPs alone was insufficient to protect the enzyme from the action of captan. Furthermore, the interaction of [14C]captan with the beta and beta' subunits was not prevented by a similar preincubation. Captan also bound, to a lesser extent, to the alpha and sigma subunits. Therefore, captan binding appears to involve interaction with RNA polymerase at sites in addition to those for DNA and NTP; however, this action does not inhibit the polymerase activity.

1,8-Naphthalic anhydride antidote enhances the toxic effects of captan and thiram fungicides on Azospirillum brasilense cells.

The effects of ten fungicides, six herbicides and four insecticides on the nitrogen-fixing bacterium Azospirillum brasilense were examined. The fungicides captan and thiram were the most toxic among the compounds tested. Cell growth and nitrogenase activity of the bacterium were markedly inhibited by low concentrations of the two fungicides. Antidote 1,8-naphthalic anhydride increased by a factor of 2 the cellular level of glutathione. The addition of the antidote in the presence of captan or thiram caused a similar increase in the glutathione content, but at the same time enhanced the toxicity of the two fungicides.