Dinitroaniline Herbicides Research Articles

Effect of Trifluralin, Zero-Valent Iron and Magnetite Nanoparticles on Growth of Micromycetes

Abstract Nowadays many reports confirmed the effect of different nanoparticles (NPs) on the growth and secondary metabolite production in various microorganisms. Some of them, NPs like Ag, Au and oxides of Al, Ti, Si and Zn have harmful effect on the cells of microorganisms. Iron NPs are expected to be nontoxic, due to using Fe atom in several pathways of cell metabolism and, therefore, low iron toxicity. The use of iron NPs in technologies for remedying polluted environment was caused by their efficiency in reduction reactions, mobility, and high reactivity, due to the high surface area. The present study aims to determine the effect of magnetite (Fe3O4), zero-valent iron Fe(0) NPs, and fluorinated dinitroaniline herbicide trifluralin on growth of mycelial fungi. Fungal strains were isolated from soil long-term polluted with obsolete pesticides, DDT and trifluralin. The inhibition activity of iron NPs and trifluralin was evaluated using express-method. Each fungal strain had an individual reaction to the solutions of iron nanoparticles. At the same time, Fe(0) NPs, as well as magnetite NPs, had a stimulating effect on the formation and maturation of spores of micromycetes. Addition of trifluralin to the culture medium had a growth inhibition effect on micromycetes, but this effect was reduced, when trifluralin was mixed and incubated with iron NPs for 1 hour before.

Synthesis of a hybrid organic-inorganic polyethersulfone membrane incorporated with phosphotungstic acid: Controversial performance in removal of dinitroaniline herbicides from water

Abstract Present study focused on removal of one type of highly employed and poisonous herbicides (trifluralin and ethalfluralin as dinitroaniline herbicides) from water using membrane technology. To this aim, composite membranes were prepared using polyethersulfone as base polymer and different concentrations of phosphotungstic acid as superhydrophilic additive. Scanning electron microscopy, atomic force microscopy, water contact angle, bulk porosity and mean pore size measurements as well as pure water tests were employed for characterization of membranes. To mimic real circumstances existing in surface water, experiments were conducted at acid, neutral and basic pHs, and also, effects of ionic environment on removal of herbicides was probed by controlling the sodium and calcium concentration in feed solution. Water permeability was remarkably improved due to induced changes in composite membranes. Surprisingly, fabricated membranes behaved contrarily in removal of dinitroanilines belonged to the same class of herbicides with similar size and molecular weight. According to the results, efficiency of membranes was affected by several factors relating to both membrane and herbicide as well as solution pH. Moreover, evaluation of antifouling characteristics of membranes demonstrated higher resistance of composite membranes against fouling.

Novel α-Tubulin Mutations Conferring Resistance to Dinitroaniline Herbicides in Lolium rigidum.

The dinitroaniline herbicides (particularly trifluralin) have been globally used in many crops for selective grass weed control. Consequently, trifluralin resistance has been documented in several important crop weed species and has recently reached a level of concern in Australian Lolium rigidum populations. Here, we report novel mutations in the L. rigidum α-tubulin gene which confer resistance to trifluralin and other dinitroaniline herbicides. Nucleotide mutations at the highly conserved codon Arg-243 resulted in amino acid substitutions of Met or Lys. Rice calli transformed with the mutant 243-Met or 243-Lys α-tubulin genes were 4- to 8-fold more resistant to trifluralin and other dinitroaniline herbicides (e.g., ethalfluralin and pendimethalin) compared to calli transformed with the wild type α-tubulin gene from L. rigidum. Comprehensive modeling of molecular docking predicts that Arg-243 is close to the trifluralin binding site on the α-tubulin surface and that replacement of Arg-243 by Met/Lys-243 results in a spatial shift of the trifluralin binding domain, reduction of trifluralin-tubulin contacts, and unfavorable interactions. The major effect of these substitutions is a significant rise of free interaction energy between α-tubulin and trifluralin, as well as between trifluralin and its whole molecular environment. These results demonstrate that the Arg-243 residue in α-tubulin is a determinant for trifluralin sensitivity, and the novel Arg-243-Met/Lys mutations may confer trifluralin resistance in L. rigidum.

Dinitroaniline herbicide resistance in a multiple-resistant Lolium rigidum population.

The pre-emergence dinitroaniline herbicides (such as trifluralin and pendimethalin) are vital to Australian no-till farming systems. A Lolium rigidum population collected from the Western Australian grain belt with a 12-year trifluralin use history was characterised for resistance to dinitroaniline, acetyl CoA carboxylase (ACCase)- and acetolactate synthase (ALS)-inhibiting herbicides. Target-site resistance mechanisms were investigated. This L. rigidum population exhibited 32-fold resistance to trifluralin, as compared with the susceptible population. It also displayed 12- to 30-fold cross-resistance to other dinitroaniline herbicides (pendimethalin, ethalfluralin and oryzalin). In addition, this population showed multiple resistance to commonly used post-emergence ACCase- and ALS-inhibiting herbicides. Two target-site α-tubulin gene mutations (Val-202-Phe and Thr-239-Ile) previously documented in other dinitroaniline-resistant weed species were identified, and some known target-site mutations in ACCase (Ile-1781-Leu, Asp-2078-Gly and Cys-2088-Arg) and ALS (Pro-197-Gln/Ser) were found in the same population. An agar-based Petri dish screening method was established for the rapid diagnosis of resistance to dinitroaniline herbicides. Evolution of target-site resistance to both pre- and post-emergence herbicides was confirmed in a single L. rigidum population. The α-tubulin mutations Val-202-Phe and Thr-239-Ile, documented here for the first time in L. rigidum, are likely to be responsible for dinitroaniline resistance in this population. Early detection of dinitroaniline herbicide resistance and integrated weed management strategies are needed to maintain the effectiveness of dinitroaniline herbicides. © 2017 Society of Chemical Industry.

In vitro genotoxicity assessment of dinitroaniline herbicides pendimethalin and trifluralin

Pendimethalin and trifluralin are widely used dinitroaniline herbicides. Both compounds can be found as residue levels in agricultural products. This study was conducted in order to provide necessary information for the risk assessment of pendimethalin and trifluralin. In this study, reactive oxygen species (ROS) levels were measured to examine the potential of both compounds to induce oxidative damage in Chinese hamster lung fibroblast (V79) cells. Also, the genotoxic effects of pendimethalin and trifluralin at the concentration range of 1-500 μM was determined. Single cell gel electrophoresis (comet) and micronucleus assays were used on human peripheral lymphocytes and V79 cells for the genotoxicity assessment. The cell viability of two dinitroaniline herbicides were determined by the use of neutral red uptake assay on V79 cells. IC50 values were determined as 66 μM and 128 μM for pendimethalin and trifluralin, respectively. They significantly increased ROS levels on V79 cells for 1-24 h. Both herbicides significantly induced the DNA damage and showed genotoxicity on lymphocytes and V79 cells. Micronucleus frequency increased significantly after pendimethalin and trifluralin treatment of the lymphocytes and V79 cells. Therefore, we concluded that both of the herbicides induced the genotoxicity through the activation of oxidative stress pathway and chromosomal damage.

Pendimethalin induces oxidative stress, DNA damage, and mitochondrial dysfunction to trigger apoptosis in human lymphocytes and rat bone-marrow cells.

Pendimethalin (PM) is a dinitroaniline herbicide extensively applied against the annual grasses and broad-leaved weeds. There is no report available on PM-induced low-dose genotoxicity in human primary cells and in vivo test models. Such data gap has prompted us to evaluate the genotoxic potential of PM in human lymphocytes and rats. PM selectively binds in the minor groove of DNA by forming covalent bonds with G and C nitrogenous bases, as well as with the ribose sugar. PM induces micronucleus formation (MN) in human lymphocytes, indicating its clastogenic potential. Comet assay data showed 35.6-fold greater DNA damage in PM (200μM)-treated human lymphocytes. Rat bone-marrow cells, at the highest dose of 50mg/kg bw/day of PM also exhibited 10.5-fold greater DNA damage. PM at 200μM and 50mg/kg bw/day induces 193.4 and 229% higher reactive oxygen species generation in human lymphocytes and rat bone-marrow cells. PM-treated human lymphocytes and rat bone-marrow cells both showed dysfunction of mitochondrial membrane potential (ΔΨ m). PM exposure results in the appearance of 72.2 and 35.2% sub-G1 apoptotic peaks in human lymphocytes and rat bone-marrow cells when treated with 200μM and 50mg/kg bw/day of PM. Rats exposed to PM also showed imbalance in antioxidant enzymes and histological pathology. Overall, our data demonstrated the genotoxic and apoptotic potentials of PM in human and animal test models.

Target-Site Point Mutation Conferring Resistance to Trifluralin in Rigid Ryegrass (Lolium rigidum)

Populations of rigid ryegrass suspected of resistance to trifluralin due to control failures exhibited varying levels of susceptibility to trifluralin, with 15 out of 17 populations deemed resistant (>20% plant survival). Detailed dose–response studies were conducted on one highly resistant field-evolved population (SLR74), one known multiply resistant population (SLR31), and one susceptible population (VLR1). On the basis of the dose required to kill 50% of treated plants (LD50), SLR74 had 15-fold greater resistance than VLR1, whereas, the multiply resistant SLR31 had 10-fold greater resistance than VLR1. Similarly, on the basis of dose required to reduce shoot biomass by 50% (GR50), SLR74 had 17-fold greater resistance than VLR1, and SLR31 had 8-fold greater resistance than VLR1. Sequencing of the α-tubulin gene from resistant plants of different populations confirmed the presence of a previously known goosegrass mutation causing an amino acid substitution at position 239 from threonine to isoleucine in resistant population SLR74. This mutation was also found in 4 out of 5 individuals in another highly resistant population TR2 and in 3 out of 5 individuals of TR4. An amino acid substitution from valine to phenylalanine at position 202 was also observed in TR4 (3 out of 5 plants) and TR2 (1 out of 5 plants). There was no target-site mutation identified in SLR31. This study documents the first known case of field-evolved target-site resistance to dinitroaniline herbicides in a population of rigid ryegrass.

Controlling Dinitroaniline-Resistant Goosegrass (Eleusine indica) in Turfgrass

Prodiamine is a dinitroaniline herbicide labeled for PRE control of goosegrass in warm- and cool-season turfgrass. In 2013, several golf course roughs in Maryville, TN reported poor goosegrass control (< 20%) following prodiamine treatment at 1,120 g ai ha-1. We harvested suspected prodiamine-resistant (PR) and prodiamine-susceptible (S) goosegrass phenotypes from the field and exposed them to a range of increasing prodiamine concentrations in hydroponic culture. Exposure to prodiamine at 0.001 mM reduced root growth of the S phenotype to 11% of the non-treated check. By comparison, exposure to 0.001 mM prodiamine had minimal effect on the PR phenotype, as root growth was 94% of the non-treated check. Molecular analyses revealed that PR plants contained a threonine (Thr) to isoleucine (Ile) substitution at position 239 on the α-tubulin 1 (TUA1) protein. The substitution, found in all PR plants, is the mechanism of prodiamine resistance in this phenotype. In field studies, topramezone controlled PR goosegrass 72% to 89% by 50 d after treatment (DAT) compared to only 22% to 23% for foramsulfuron. Topramezone treatment injured bermudagrass 34% to 60% from 7 to 14 DAT; however, injury was≤6% 28 DAT and 0% by the end of the study. Our results indicate that POST applications of topramezone can control dinitroaniline-resistant goosegrass. In addition, we established an easy-to-use genotyping assay to quickly screen goosegrass phenotypes for a target-site mutation (Thr-239-Ile) on TUA1 associated with resistance to dinitroaniline herbicides such as prodiamine. Future research should work to expand this assay for use with other weed species and herbicidal modes of action.

Assessment of Genotoxic Effects of Pendimethalin in Chinese Hamster Over Cells by the Single Cell Gel Electrophoresis (Comet) Assay.

Pendimethalin (N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzeneamine) is a dinitroaniline herbicide compound which selectively controls weeds. It is a cell division and growth inhibitor. It descends plants in a short time after seedling. It is a soil and water pollutant due to the widespread use of formulations in Turkey and around the world. Pendimethalin is manufactured in and imported by Turkey. Pendimethalin is a slightly toxic compound that is classified in toxicity class 3 by the United States Environmental Protection Agency (USEPA). Even though it is classified as group C (human possible carcinogen) compound by the USEPA, there are limited number of studies about its genotoxic effects. The aim of this study was to evaluate in vitro genotoxic effects of different concentrations of pendimethalin in Chinese hamster over (CHO) cells by the single cell gel electrophoresis (comet) assay. The cells are incubated with 1, 10, 100, 1000 and 10000 µM concentrations of pendimethalin for 30 min at 37°C and DNA damage was compared with CHO cells untreated with pendimethalin. 50 µM hydrogen peroxide was used as positive control. No significant cytotoxic effects were observed within the concentration ranges studied. The DNA damage in CHO cells was significantly increased in the pendimethalin concentrations of 1, 100, 1000 and 10000 µM, however, a significant decrease was observed in 10 µM pendimethalin concentration. Our results show that 1-10000 µM concentrations of pendimethalin induce DNA damage in CHO cells, which was assessed by comet assay.

Pendimethalin Nitroreductase Is Responsible for the Initial Pendimethalin Degradation Step in Bacillus subtilis Y3.

Pendimethalin [N-(1-ethylpropyl)-2,6-dinitro-3,4-xylidine] is a widely used selective preemergence dinitroaniline herbicide, and its residue has been frequently detected in the environment. The U.S. Environmental Protection Agency (EPA) has classified pendimethalin as a persistent bioaccumulative toxin. To date, no enzymes or genes involved in pendimethalin biodegradation have been reported. In the present study, the gene pnr, which encodes the nitroreductase PNR, responsible for the nitroreduction of pendimethalin, was cloned from the pendimethalin-degrading strain Bacillus subtilis Y3. PNR could also catalyze the nitroreduction of three other major varieties of dinitroaniline herbicides, including butralin, oryzalin, and trifluralin. The reduction of pendimethalin by PNR might eliminate its toxicity against Saccharomyces cerevisiae BY4741, indicating the application potential of PNR in the detoxification of pendimethalin.

Methylation and acetylation profiles of dinitroaniline herbicides and resveratrol on V79 cell line

Methylation and acetylation profiles of dinitroaniline herbicides and resveratrol on V79 cell line

Abiotic reduction of trifluralin and pendimethalin by sulfides in black-carbon-amended coastal sediments

Dinitroaniline herbicides such as trifluralin and pendimethalin are persistent bioaccumulative toxins to aquatic organisms. Thus, in-situ remediation of contaminated sediments is desired. This study investigated whether black carbons (BCs), including apple wood charcoal (BC1), rice straw biochar (BC2), and activated carbon (BC3), could facilitate abiotic reduction of trifluralin and pendimethalin by sulfides of environmentally-relevant concentrations in anoxic coastal sediments. The reduction rates of trifluralin and pendimethalin increased substantially with increasing BC dosages in the sediments. This enhancing effect was dependent on BC type with the greatest for BC3 followed by BC1 and BC2, which well correlated with their specific surface area. The pseudo-first order reduction rate constants (kobs) for BC3-amended sediment (2%) were 13- and 14 times the rate constants in the BC-free sediment. The reduction rates increased with increasing temperature from 8 to 25°C in the BC-amended sediment, following the Arrhenius relationship. Finally, through molecular modeling by density functional theory and reaction species identification from mass spectra, molecular pathways of trifluralin and pendimethalin reduction were elucidated. In contrary to the separate sequential reduction of each nitro group to amine group, both nitro groups, first reduced to nitroso, then eventually to amine groups.

옥수수 일차뿌리에서 oryzalin이 굴중성 반응과 에틸렌 생성에 미치는 효과

Oryzalin은 미세소관을 분열시키는 dinitroaniline계의 제초제이다. 미세소관과 미세섬유는 평형석 침강과 세포벽을 구성하는 세포골격들이다. 평형석은 뿌리 끝에 있는 columella 세포에서 중력 인지 조절을 한다. 본 연구는 oryzalin이 옥수수 일차 뿌리에서 ethylene 생성을 통하여 굴중성 반응에 미치는 영향을 연구하였다. 뿌리 끝 부분에 10^-4 M oryzalin의 처리는 뿌리 성장과 굴중성 반응을 저해하였으나, 신장대에 처리하게 되면 저해현상은 관찰되지 않았다. 10^-4 M oryzalin을 뿌리 끝에 15시간 처리하면 뿌리 끝의 생장이 억제되고 둥근 형태로 부풀었다. 에틸렌의 전구물질인 ACC를 뿌리 끝에 처리하여도 굴중성 반응이 억제되었다. Oryzalin의 작용과 에틸렌 생성에 대한 관련성을 연구하기 위하여 oryzalin 처리 후 에틸렌 생성을 측정하였다. Oryzalin 처리에 의해 ACC oxidase와 ACC synthase의 활성이 증가되어 에틸렌 생성이 촉진되었다. Oryzalin은 ACO와 ACS의 유전자의 발현도 증가 시켰다. Indole-3-acetic acid (IAA)는 굴중성 반응 동안 관찰되는 비 대칭적 신장에 중요한 역할을 한다. 이러한 연구 결과는 oryzalin이 뿌리 끝에서 IAA transport를 억제하여 뿌리 신장대의 윗면과 아랫면의 IAA 양의 차이를 감소시키고, 또한 에틸렌 생성을 촉진하며 미세소관의 배열을 방해하여 뿌리 글중성과 생장을 억제할 가능성을 제시하고 있다. Oryzalin is a dinitroaniline herbicide, which disrupts the arrangement of microtubules. Microtubules and microfilaments are cytoskeletal components that are thought to play a role in the sedimentation of statoliths and the formation of cell walls. Statoliths regulate the perception of gravity by columella cells in the root tip. To determine the effect of oryzalin on the gravitropic response, ethylene production in primary roots of maize was investigated. Treatment with 10^-4 M oryzalin to the root tip inhibited the growth and gravitropic response of the roots. However, the treatment had no effect on the elongation zone of the roots. An application of 10^-4 M oryzalin for 15 hr to the root tip caused root tip swelling. The application of 1-aminocycopropane-1-carboxylic acid (ACC), a precursor of ethylene, to the root tip also inhibited the gravitropic response. To understand the role of oryzalin in the regulation of the growth and gravitropic response of roots, ethylene production in the primary roots of maize was measured following treatment with oryzalin. Oryzalin stimulated ethylene production via the activation of ACC oxidase (ACO) and ACC synthase (ACS), and it increased the expression of ACO and ACS genes. Indole-3-acetic acid (IAA) played a key role in the asymmetric elongation rates observed during gravitropism. The results suggest that oryzalin alters the gravitropic response of maize roots through modification of the arrangement of microtubules. This might reduce the distribution of IAA in the upper and lower sides of the elongation zone and increase ethylene production, thereby inhibiting growth and gravitropic responses.

Purification and properties of pendimethalin nitroreductase from Bacillus circulans

A pendimethalin nitroreductase was purified from Bacillus circulans to 52-fold increase with a recovery of 21.1% and had a specific activity of 4.16 U/mg. The molecular weight was 27 kDa. The optimum pH and temperature were 7.5 and 35°C, respectively. Fe2+, Ca2+, Mg2+ and Mn2+ did not cause any effect on the enzyme activity, whereas Ag+, Hg2+ significantly inhibited it. The pendimethalin nitroreductase from B. circulans required NADPH as cofactor. It was not affected by GSH, DTT, L-Cys and β-mercaptoethanol but inhibited by p-hydroxymercuribenzoate, N-ethylmaleimide, and iodoacetamide. EDTA, 1,10-phenanthroline and α,α′-dipyridyl had a moderate effect on the enzyme activity. The nitroreductase reduced all the tested nitroaromatic compounds but was more active towards pendimethalin and trifluralin. The KM and Vmax for the enzyme reaction using pendimethalin as a substrate were 4.35 μM and 620 μmoles mg−1 min−1, respectively. The broad substrate specificity towards dinitroaniline herbicides suggested the enzyme to be used as a potent reducing agent of these toxic compounds. This is the first report for the purification and characterization of pendimethalin nitroreductase from any bacterial or fungal species.

Analysis of 7 Dinitroaniline Residues in Complex Food Matrices by GC–NCI/MS

A modified quick, easy, cheap, effective, rugged, and safe sample preparation method combined with gas chromatography–negative chemical ionization–mass spectrometry (GC–NCI/MS) has been developed for the determination of 7 dinitroaniline herbicide residues in complex matrices (garlic, olive oil, scallion, leek and chili). Dinitroaniline residues were extracted with hexane-saturated acetonitrile. After the cleanup with the dispersive solid-phase extraction, the extract was analyzed by GC–NCI/MS in selected ion monitoring mode. Two isotope internal standards (trifluralin-d 14 and pendimethalin-d 5) were employed for quantification. Compared with electron ionization (EI) mode, the superiorities of NCI in sensitivity and selectivity were investigated. Limits of the detection of 7 dinitroanilines were in the range of 0.014–0.096 μg kg−1, and there were no interfering peaks (unlike in EI) in the complex matrices. Recoveries of 7 dinitroanilines in five matrices at three spiked levels (10, 20 and 40 μg kg−1) ranged from 61 to 126 % and the relative standard deviations were all below 12 %.

Efficacy of Preemergence Herbicides for Controlling a Dinitroaniline-Resistant Goosegrass (Eleusine indica) in Georgia

Goosegrass is a problematic weed in turfgrass, and overuse of dinitroaniline (dna) herbicides has resulted in evolution of resistant populations. The objectives of this research were to (1) evaluate responses of a susceptible (S) goosegrass compared to a suspected resistant (R) biotype from Griffin, GA to prodiamine, and (2) evaluate efficacy of various PRE herbicides for control. Prodiamine rates required for 50% control and 50% shoot reductions after 6 wk for R-goosegrass measured > 13.44 and 3.2 kg ai ha−1, respectively, whereas rates for the S-population measured 0.45 and < 0.42 kg ha−1, respectively. In field experiments, sequential applications of dithiopyr and prodiamine provided < 20% control of R-goosegrass over 2 yr. Single applications of dimethenamid-P at 1.68 kg ai ha−1provided < 50% goosegrass control in 2011 but provided excellent control (≥ 90%) at 7 mo after initial treatments (MAIT) in 2012. Single and sequential applications of indaziflam provided excellent control of goosegrass in both years, and oxadiazon controlled goosegrass > 85% at 7 MAIT in 2011 and ≥ 90% in 2012. Single and sequential PRE sulfentrazone applications controlled goosegrass < 60% in 2011 but averaged 94% control in 2012. Overall, indaziflam and oxadiazon provided good (80 to 89%) to excellent control of dna-resistant goosegrass in both years, but dimethenamid and sulfentrazone were inconsistent.

Adsorption of pesticide benfluralin at the electrochemical interface

The adsorption behaviour of a dinitroaniline herbicide benfluralin was studied by means of electrochemical as well as scanning probe techniques. The double layer capacitance reflects very sensitively changes of the interfacial structure at the surfaces. This allows discrimination between a simple adsorption process and a slow transition of adsorbed film structure controlled by the mechanism of nucleation. The information about nucleation kinetics and growth mechanism of the film on the electrode was obtained from the time dependence of the double layer capacitance employing the mercury drop electrode. The phase transition may lead to the reorientation of the molecules within the adsorbed layer. These findings were supported by scanning tunneling microscopy.

Application of random amplified polymorphic DNA (RAPD) to detect genotoxic effect of trifluralin on maize (Zea mays)

Trifluralin is a widely used dinitroaniline herbicide throughout the world. However, limited efforts have been made to study its genotoxic effects on different plants. The present study aimed to evaluate the herbicide’s genotoxic potential on maize (Zea mays) by using the random amplified polymorphic DNA (RAPD) technique. For this purpose, maize seedlings were treated with aqueous solutions of trifluralin at concentrations ranging from 0.5 to 3 ppm for 7 days. In the RAPD analyses, 15 primers were used and 91 bands were obtained, with an average of 6.06 bands per primer in the control seedlings. After trifluralin treatment, significant changes were observed in RAPD profiles. These changes included loss of normal bands and appearance of new bands, in comparison to the control group, and they were dose dependent. In addition, root growth and total soluble protein level in trifluralin-treated seedlings were analyzed and compared for genomic template stability (GTS), which was performed for the qualitative measurement of changes in randomly amplified polymorphic DNA (RAPD) profiles. The results showed that GTS, root growth, and total soluble protein content of the seedlings gradually decreased with an increase in trifluralin concentration. These findings suggest that the RAPD technique is a useful biomarker assay to evaluate the genotoxic effects of herbicides on plants.

Effect of chronic exposure to pendimethalin on the susceptibility of rainbow trout, Oncorhynchus mykiss L., to viral hemorrhagic septicemia virus (VHSV)

In this study, the in vivo effects of chronic pollution by the active substance (AS) pendimethalin, a dinitroaniline herbicide, on the susceptibility of rainbow trout, Oncorhynchus mykiss L., to an experimental challenge with viral hemorrhagic septicemia virus (VHSV) were assessed. After four weeks of exposure to fresh water (C group) or 500ngL−1 of AS (P500 group), the fish were challenged by immersion in water containing 104TCID50mL−1 of VHSV. While exposure to pendimethalin was maintained throughout the experiment, mortalities were recorded during the 40 days post-infection (dpi) and organs were collected from dead fish for virological examination. At the end of the experiment, anti-VHSV antibodies and the classical pathway of complement activity were assessed in trout plasma.Exposure to pendimethalin significantly affected the distribution of cumulative mortality accelerating death in fish infected by VHSV. Pendimethalin appeared to decrease the Mean Time to Death (MTD) after virus treatment from 14.9 days (C-VHSV) to 10.2 days (P500-VHSV). Nevertheless, by the end of the experiment, differences in cumulative mortality were no longer observed between the two groups, which had reached the same stage (50 percent). Furthermore, a higher concentration of the virus was recovered from the pools of organs from the P500-VHSV group than the C-VHSV group. Moreover, at 40dpi, although no significant difference was observed in the immune response between the two groups, more fish in the P500-VHSV group had set up an immune response by secreting antibodies than in the control viral group (C-VSHV).

Soil application of dinitroaniline and arylphenoxy propionic herbicides influences the activities of phosphate-solubilizing microorganisms in soil

An experiment was conducted under laboratory conditions to investigate the effect of two systemic herbicides, viz. pendimethalin (a dinitroaniline) and quizalofop (an arylphenoxy propionic acid) at their recommended field application rates (1.0 kg and 50 g active ingredient per hectare, respectively), either separately or in a combination, on growth and activities of phosphate-solubilizing microorganisms in relation to their effects on biochemical transformations and availability of organic carbon, total and available phosphorus in a Typic Haplustept soil of West Bengal, India. Application of herbicides, in general, significantly stimulated the growth and activities of phosphate-solubilizing microorganisms which increased microbial biomass resulting in higher accumulation of oxidizable organic carbon, total and available phosphorus in soil as compared to untreated control. The combined application of both the herbicides highly stimulated the proliferations of phosphate-solubilizing microorganisms, while pendimethalin alone significantly accentuated phosphate-solubilizing capacities 36.4% as compared to untreated control and retained highest amount of total phosphorus due to greater microbial activities in soil. The separate application of quizalofop also manifested an induced effect on the proliferations of phosphate-solubilizing microorganisms and accounted significant amounts of organic carbon and available phosphorus in the soil system. The results of the present study thus indicated that the cited herbicides at their field application rates can be safely used to eradicate weeds in the crop fields.