Toxic effects of acephate on Paramecium caudatum with special emphasis on morphology, behaviour, and generation time

The continuous increase in the number of new chemicals as well as the discharges of solid and liquid wastes triggered the need for simple and inexpensive bioassays for routine testing. In recent years, there has been increasing development of methods (particularly rapid tests) for testing environmental samples. This paper describes the quick toxic evaluation of an organophosphorus insecticide, acephate (O,S-dimethyl acetylphosphoramidothioate) on Paramecium caudatum for acute and sub-acute toxicity studies with reference to morphology, behaviour, and its generation time. The lethal concentrations for 10 min and 2 h were determined by probit method, as 500 mg L⁻¹ and 300 mg L⁻¹, respectively. Higher concentrations of 10 min exposure caused cell lysis with disintegration of cell membrane and precipitation of protoplasm. Combination of conventional light microscopy and computerized video tracking systems were used to study the locomotor behaviour of paramecia. The test organism was under stress and exhibited an initial increase and subsequent decrease in the swimming speed when exposed to 1/4, 1/2, 3/4, and LC₅₀ concentrations for 10 min (125, 250, 375, and 500 mg L⁻¹, respectively). Similar changes were also noticed when paramecia were exposed to LC₅₀ for 2 h. In a separate set of experiments, the number of generations and generation time in 24 h was evaluated with respect to the different sub-lethal concentrations (30, 60, 120, and 240 mg L⁻¹). The number of generations decreased and generation time extended significantly in a concentration dependent manner. The results indicate that the Paramecium toxicity assay could be used as a complimentary system to rapidly elucidate the cytotoxic potential of insecticides. The major advantages associated with these tests are: they are inexpensive, simple, user-friendly, space saving, and seem to be attractive alternatives to conventional bioassays.     

Oxygen consumption and ammonia excretion of the freshwater crab Trichodactylus borellianus exposed to chlorpyrifos and endosulfan insecticides

The effects of lethal and sublethal concentrations of chlorpyrifos and endosulfan on oxygen consumption and ammonia excretion rate of the crab Trichodactylus borellianus were evaluated. Oxygen consumption and energy expenditure had significant effect in relation to exposure times. Regarding endosulfan, a significant difference in consumption among times of exposure was registered in 625 μg L⁻¹. Moreover, at the highest concentration, energy expenditure rate was observed stabilized during 1–3 h. A significant increase in ammonia excretion was evidenced in 150 and 300 μg L⁻¹ of chlorpyrifos. The O:N ratio showed a decrease in chlorpyrifos and in 2500 μg L⁻¹ of endosulfan. This indicated a shift towards protein primary metabolism. An increment in the O:N ratio was observed in the lower endosulfan solutions. The relation oxygen:nitrogen showed a shift towards lipid and carbohydrate primary metabolism. This work indicated the complexity of the metabolism in the freshwater crab affected by xenobiotic elements.     

Retraction notice to “Fluctuations of certain biochemical constituents and markers enzymes as a consequence of monocrotophos toxicity in the edible freshwater fish, Channa punctatus” [Pesticide Biochemistry and Physiology 94 (2009) 5-9]

A total of 185 hexanic, dichloromethanic, ethanolic and hydroethanolic extracts from 24 species of Cerrado plants, were tested against Zabrotes subfasciatus, Acanthoscelides obtectus, and human saliva α-amylases. Twelve crude extracts presented inhibition rates greater than 80% against digestive α-amylases of the insect pest Z. subfasciatus, at a concentration of 1 mg mL⁻¹. These extracts were also tested against A. obtectus and human saliva α-amylases to verify their affinity and specificity of action. The hydroethanolic Kielmeyera coriacea stem bark extract presented a strong inhibitory potential, with IC₅₀ values of 110 μg mL⁻¹ for Z. subfasciatus and 272.12 μg mL⁻¹ for A. obtectus, in addition to a 97.09% reduction in enzyme activity of human saliva α-amylases at 125 μg mL⁻¹. The hexanic Aspidosperma macrocarpon root wood extract totally inhibited the activity of Z. subfasciatus α-amylases, reduced the enzyme activity of A. obtectus by 14.69% at 1 mg mL⁻¹, but did not alter the activity of human saliva α-amylases, thus characterizing greater inhibition affinity and specificity. The results suggest that the application of plant extracts against insect α-amylases represent a promising biotechnological tool for development of new insect pest control strategies, with noticeable affinity and specificity of action against different target enzymes.     

Nile tilapia (Oreochromis niloticus), liver morphology,CYP1A activity and thyroid hormones after Endosulfan dietary exposure

Endosulfan is a worldwide used insecticide suspected to be highly toxic to aquatic organisms, including fish. Most of the available studies have focused in water exposures, although this pollutant can be transferred through food chain. Therefore, in the present study, the effects of Endosulfan on tilapia (Oreochromis niloticus), when administered through the diet. Fish were fed 21 days with diets containing 1 and 0.5 μg g⁻¹ of Endosulfan, after which qualitative histological liver analysis showed that Endosulfan induced hepatocyte destruction, vessel endothelium rupture and increased melanomacrophages aggregates. To test lower environmentally relevant doses of Endosulfan could induce hepatic damage, as well as other negative effects, such as altered phase I metabolism and plasma thyroid hormone levels. Hence, tilapia were orally exposed to 0.1 and 0.001 μg g⁻¹ for 35 days. Low environmentally realistic doses of Endosulfan were still able to induce liver histopathological damage such as increased hepatocyte vacuolization and increased eosinophil granular cell aggregates. Liver cytochrome P450 1A activity, evaluated through ethoxyresorufin-o-deethylase (EROD), was enhanced in tilapia exposed to 0.001 μg g⁻¹, whereas the highest dose had no measurable effects in this enzyme activity. Fish exposed to 0.1 μg g⁻¹ of Endosulfan had depressed T4 plasma levels. Overall, the results of the present study further demonstrate the toxic effects of Endosulfan in tilapia when administered in the diet at environmentally relevant concentrations, which indicates that in the field food chain transfer may also be an importance source of this pollutant.     

Comparative molluscicidal action of extract of Ginko biloba sarcotesta,arecoline and niclosamide on snail hosts of Schistosoma japonicum

In search for new local plant molluscicides for the control of the vectors of schistosomiasis, we compared the molluscicidal action of the extract of Ginkgo biloba sarcotesta by benzinum (EGSB) to that of arecoline (ARE) and niclosamide (NIC) against Oncomelania hupensis snails. NIC showed the highest toxicity on snails with 24 h LC₅₀ vales of 0.12 mg/L and LC₉₀ of 0.98 mg/L, while the LC₅₀ and LC₉₀ of EGSB were much lower than that of ARE. Sublethal in vivo 24 h exposure to 40% and 80% LC₅₀ of NIC, EGSB and ARE altered the activities of different enzymes in different body tissues of snails. EGSB could significantly inhibit Choline esterase (ChE), Alanine aminotransferase (ALT), Alkaline phosphatase (ALP) and Malic dehydrogenase (MDH) activities both in the cephalopodium and liver. ARE could significantly cause a reduction in ChE, ALP activities in the cephalopodium and ChE, ALT, ALP, Succinodehydrogenase (SDH), MDH activities in the liver. NIC significantly altered activities of ChE, ALT, ALP, SDH, and MDH in the cephalopodium and ChE, ALT, ALP, SDH activities in the liver. All molluscicides could not affect Lactate dehydrogenase (LDH) activity in the cephalopodium and the liver. Maximum inhibition of ALT and MDH activities was found in the cephalopodium and liver of snails treated with 80% of 24 h LC₅₀ of EGSB. However, NIC and ARE caused maximum reduction in ALP and SDH activities, respectively. The results indicated that molluscicidal action of EGSB was different to that of ARE and NIC in some extent.     

Physiological and molecular mechanisms of glyphosate tolerance in an in vitro selected cotton mutant

We have selected an upland cotton (Gossypium hirsutum L.) cell line (R1098) that is highly tolerant to glyphosate. This cell line was developed by in vitro selection with gradually increasing glyphosate concentrations, and its mechanisms conferring glyphosate tolerance were studied. Based on a whole-plant dose–response bioassay, R1098 plants were tolerant to glyphosate at a concentration of 1500 g ae ha⁻¹ glyphosate (1.5× the recommended field rate) whereas the control plants (Coker 312) were unable to survive at 150 g ae ha⁻¹ glyphosate. Coker 312 accumulated 13.1 times more shikimate in leaves at 5 days after glyphosate treatment (1500 g ae ha⁻¹) than that of R1098. Two distinct cDNAs for 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), EPSPS-1 and EPSPS-2, were isolated from R1098. Both cDNAs were 97.7% identical within the common protein-coding region and the predicted sequences of the mature proteins were greater than 83% identical with EPSPS proteins from other known higher plants. In comparison to the glyphosate-susceptible cotton Coker 312, sequence analysis of the EPSPS-1 gene indicated that R1098 has an alanine insertion at nucleotide position 1216 resulting in frameshift. It leads to two copy functional EPSPS genes in R1098. There was no difference between R1098 and Coker 312 in EPSPS mRNA levels before glyphosate treatment. However, its treatment caused a 2–4 times increase in the basal EPSPS mRNA level in R1098.     

Agrobacterium induces plant cell death in wheat (Triticum aestivum L.)

The symptoms of gall or hairy root do not occur in the interactions between wheat (Triticum aestivum L.) and other monocotyledonous plants, with Agrobacterium tumefaciens or Agrobacterium rhizogenes. However, both bacteria colonized wheat root surfaces at similar levels (2.0 × 10⁷ colony forming U g⁻¹ root) and grew without inhibition in suspension with intact or wounded wheat embryos or root segments present. Suspension-cultured wheat embryo cells grown in 7.4 m M O₂ displayed 23% cell death after 1 h exposure to Agrobacterium cells, while the extent of cell death with 2.1 m M O₂ averaged 8%. Cultured wheat embryo and root cells rapidly produced hydrogen peroxide (H₂O₂) when contacted with A. tumefaciens or A. rhizogenes. Production of H₂O₂ was lower at 2.1 m M O₂ than 7.4 mM O₂. Browning and autofluorescence of epidermal cells of callus derived from wheat embryos and wheat roots was observed after inoculation with Agrobacterium. An increase in ferulic acid was detected in the walls of roots exposed to Agrobacterium. However, neither lignin nor callose was detected by diagnostic staining methods. These findings suggest that Agrobacterium induced a resistance-like response in wheat that may reduce the efficacy of transformation and limit the normal symptom formation.     

Chlorpyrifos induced alterations in the levels of hydrogen peroxide,nitrate and nitrite in rat brain and liver

Organophosphate pesticides are among the most widely used synthetic chemicals for controlling a wide variety of pests. Chlorpyrifos (CPF) is among the leading organophosphate (OP) pesticides used extensively throughout the world including India. Besides being potent anticholinesterase compounds, these OP pesticides are known to generate oxidative stress. Present study was carried out to see the level of reactive oxygen species (ROS), hydrogen peroxide (H₂O₂), nitrate (NO₃⁻) and nitrite (NO₂⁻) in different parts of rat brain and liver after giving different doses of CPF intramuscularly for 3 days or for 1 month. Results of the present study clearly revealed that levels of H₂O₂, NO₃⁻ and NO₂⁻ were increased significantly in all the three parts of rat brain i.e., fore-, mid- and hind-brain as well as in liver of rats given for 3 days or 1 month due to exposure of different doses of CPF. The study clearly demonstrated that CPF generated oxidative stress in all the three brain regions as well as liver of rats and the ROS were accumulated. Accumulation of ROS in all the regions of brain and other tissues may disturb the normal physiological functions aggravating the toxicity symptoms of CPF.     

Evaluation of molluscicidal activities of Arisaema tubers extracts on the snail Oncomelania hupensis

Four extracts of Arisaema erubescens tubers by acetic acetal (AAE), benzinum (BZE), n-butanol (NBE) and chloroform (CFE) were obtained to evaluate their molluscicidal activities against the snail Oncomlania hupensis. The responses of choline esterase (ChE), alkaline phosphatase (ALP), esterase (EST), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) to the extracts (NBE) were also investigated. In the four extracts (AAE, BZE, NBE and CFE), NBE showed the highest toxicity on the snails after 48 h exposure. NBE also showed the time- and concentration-dependent effect, for example, the LC₉₀ values of the NBE were decreased from 365.5 mg/L (24 h) to 36.4 mg/L (96 h). At the end of exposure to NBE (LC₅₀ concentration), the activities of ChE and ALP in snail tissues (cephalopodium and liver) decreased significantly. Isozyme electrophoresis profiles indicated that responses of isozymes (EST, SOD and GSH-Px) to NBE were more intense in liver than in cephalopodium. After 72 h exposure to NBE, the EST activity in snail liver decreased and some enzyme bands (EST1 and EST4) disappeared. But the activities of SOD 1 and GSH 2 in liver increased after 48 h exposure. The results indicated that NBE was the highest toxic component in the four extracts. The decline of the detoxification ability and the oxidative damage in snail tissues might be the main reason for the molluscicidal activities.     

Histochemical studies on the accumulation of reactive oxygen species (O2− and H2O2) in the incompatible and compatible interaction of wheat—Puccinia striiformis f. sp. tritici

The generation and accumulation of reactive oxygen species (ROS), superoxide anion (O₂⁻) and hydrogen peroxide (H₂O₂), were studied in the interaction between wheat cv. ‘Suwon 11’ and two races of Puccinia striiformis f. sp. tritici (avirulent and virulent). Generation of O₂⁻ and H₂O₂ was analyzed histochemically using nitroblue tetrazolium (NBT) and 3,3-diamino-benzidine (DAB), respectively. At the pre-penetration stage during appressorium formation both stripe rust races induced H₂O₂ accumulation in guard cells. In the incompatible interaction, a rapid increase of O₂⁻ and H₂O₂ generation at infection sites was detected. The percentage of infection sites showing NBT and DAB staining was 36.1% and 40.0%, respectively, 12 h after inoculation (hai). At extended incubation time until 24 hai, percentage of infection sites showing H₂O₂ accumulation further increased, whereas those exhibiting O₂⁻ accumulation declined. The early infection stage from 12 to 24 hai coincided with primary haustoria formation in mesophyll cells. In contrast, in the compatible interaction, O₂⁻ and H₂O₂ generation could not be detected in most of the infection sites. In the incompatible interaction, intensive DAB staining was also determined in mesophyll cells, especially in cell walls, surrounding the infected cells 16–24 hai; thereafter, these cells contained fluorescing compounds and underwent hypersensitive response (HR). The number of necrotic host cells surrounding the infection sites increased continuously from 20 to 96 hai. It might be concluded that H₂O₂ accumulation during the early infection stage is associated with the occurrence of hypersensitive cell death and that resistance response is leading to arrest the avirulent race of the obligate stripe rust pathogen. In the compatible interaction at 96 hai, H₂O₂ accumulation was observed in mesophyll cells surrounding the rust lesion.     

Biochemical,physiological and morfological responses in common carp (Cyprinus carpio L.) after long-term exposure to terbutryn in real environmental concentration

The effects of terbutryn at concentrations of 0.02 (reported concentration in Czech rivers), 0.2, and 2.0 μg l^?1 were assessed in one-year-old common carp (Cyprinus carpio L.) exposed for 90 days. Influence on biometric parameters, hematology, biochemistry, histology, and oxidative stress was investigated. Exposure to 0.02, 0.2 and 2.0 μg l^?1 showed significant differences oxidative stress biomarkers compared to controls but exposure to 0.2 and 2.0 μg l^?1 significantly affected biochemical and hematological profiles. Long-term exposure of terbutryn in carp resulted in slight alterations in internal organs and increased reactive oxygen species formation, resulting in oxidative damage to lipids and proteins and inhibition of antioxidant capacities.     

Effect of miconazole,an antifungal agent,on allene oxide synthase: Inhibition,kinetics, and binding

We investigated the inhibition of allene oxide synthase (AOS), a key enzyme in jasmonic acid biosynthesis, by miconazole. Kinetic analysis indicated that miconazole was a mixed-type inhibitor of AOS with a K_i value of approximately 8.4 ± 0.2 μM. Analysis of the interactions between miconazole and AOS by optical difference spectroscopy revealed that miconazole binding induces type II binding spectra with a K_d value of approximately 6.0 ± 0.2 μM.     

Genetic analysis of abamectin resistance in Tetranychus cinnabarinus

The carmine spider mite is the most serious crop mite pests in China. Abamectin has been used to control insects and mites worldwide but carmine spider mites, Tetranychus cinnabarinus, had developed resistance to it. Genetic research on insecticide resistance has been fundamental for understanding the resistance development, studying resistance mechanisms, and designing appropriate resistance management strategies to control insect pests. A resistant colony of T. cinnabarinus, RRG42, was established to examine the inheritance of abamectin resistance in T. cinnabarinus. The females of T. cinnabarinus were selected for bioassay using a slide dip method. After 42 generations of selection, the RRG42 strain was 8.7-fold resistant to abamectin compared with the susceptible strain (SS). The logarithm (log) concentration–probit response curve for F₁s from reciprocal crosses, of F₁RS and F₁SR, were inclined to that for SS and the degree of dominance (D) values for F₁s were −0.81 and −0.17. There was a significant difference in values of LC₅₀ and slope of log concentration–probit lines between F₁RS and F₁SR. The observed mortalities of BC1 (F₁RS♀ × RRG42♂) and BC1′ (F₁SR♀ × SS♂) were significantly different from the expected mortalities based on a monogenic resistance in the chi-square tests. The inheritance of abamectin resistance in T. cinnabarinus is incompletely recessive and may be controlled by more than one gene. The maternal or cytoplasmic effect may exist in the inheritance of resistance to abamectin in T. cinnabarinus.     

Effects of trichlorfon and sodium dodecyl sulphate on antioxidant defense system and acetylcholinesterase of Tilapia nilotica in vitro

The effects of organophosphorus insecticide trichlorfon, surfactant sodium dodecyl sulphate (SDS), and the mixture of trichlorfon and SDS on the antioxidant defense system and acetylcholinesterase (AChE) in Tilapia nilotica were assessed in vitro. Various concentrations of trichlorfon (0, 0.0001, 0.001, 0.01, 0.1 and 1 g/L) and SDS (0, 0.0625, 0.125, 0.25, 0.5, 1 g/L) were incubated with homogenate of liver and muscle, respectively, at 25 °C for 0, 30, 60 and 90 min. Two concentrations of mixture of trichlorfon and SDS (0.0001 g/L trichlorfon + 0.5 g/L SDS, 0.1 g/L trichlorfon + 0.5 g/L SDS) and 0.0001 g/L trichlorfon, 0.1 g/L trichlorfon, 0.5 g/L SDS and control, were incubated simultaneously with homogenate of liver and muscle, respectively, at 25 °C for 60 min. After incubation, the content of reduced-glutathione (GSH) and the activity of superoxide dismutase (SOD), catalase (CAT) and glutathione S-transferase (GST) in homogenate of liver were determined, and the activities of AChE in homogenate of muscle were also measured.Treatment with trichlorfon caused a significant concentration-dependent and time-related inhibition of AChE activity at all treatment concentrations and times since trichlorfon is a cholinesterase inhibitor. For the same trichlorfon treatment, an apparent decrease in GSH content was found in concentration of 0.01, 0.1, 1 g/L, whereas no significant alteration in antioxidant enzyme activity were found at all experiment concentrations and times, which might indicate that antioxidant enzymes have not involved in the metabolism of trichlorfon. The depletion of GSH might indicate that ROS could be involved in the toxic effects of trichlorfon. Exposure of SDS can inhibit activities of AChE, GST and CAT at concentrations of 0.5 and/or 1 g/L, which could be due to the denaturing process of SDS to the enzymes. For the mixture exposure of trichlorfon and SDS, the effect of the mixture of 0.0001 g/L trichlorfon and 0.5 g/L SDS on inhibition of AChE shows synergistic other than simple additive of trichlorfon and SDS. The combined effects of chemicals and detergents deserve to be particularly noted. It should be noted that the toxicity experiments were made in tissue homogenates instead of whole organisms. The responses against the toxic compounds will not be the same in both systems.     

Ethylene production by Colletotrichum musae in vitro

Seven isolates of the pathogen Colletotrichum musae (Berk & Curt.) v. arx. were isolated from banana fruit. These isolates produced ethylene to varying degrees in methionine-amended Czapek Dox liquid medium as both shake and static cultures. Rates of ethylene production by C. musae were positively associated with the concentration of methionine in the growth medium. C. musae did not produce ethylene on basal medium containing l-glutamate, α -ketoglutarate or l-cysteine. Isolate CM 100 produced the highest cumulative amount of ethylene (2·27 μm g⁻¹ dry wt) over 12 days on 35 mm methionine-amended shake cultures of basal medium. In the presence of methionine, ethylene biosynthesis by C. musae occurred via 2-keto-4-methylthiobutyric acid (KMBA). The capacity of C. musae to produce ethylene may have a role in its pathogenicity on climacteric banana fruit.     

A soluble carbohydrate elicitor from Blumeria graminis f. sp. tritici is recognized by a broad range of cereals

Wheat plants rapidly recognize pathogenic and non-pathogenic conidia of the powdery mildew fungusBlumeria (syn. Erysiphe)graminis on their leaf surfaces. This suggests that a chemical signal emanates from conidia at the pre-penetration stage of infection. Conidia of B. graminis f. sp. tritici were found to contain an elicitor that was easily washed off their surface. The elicitor activity is heat stable and could not be removed by phenol extraction. By contrast, elicitor activity is sensitive to periodate oxidation and partial acid hydrolysis suggesting that the elicitor activity resides in a carbohydrate moiety. Analysis of carbohydrates revealed mostly glucose, with smaller amounts of xylose and mannose. The glucosyl residues of the B. graminis elicitor were found to be linked (1 → 2)-, (1 → 4), and (1 → 6)-, with (1 → 4, 1 → 6)- branch point residues, and no 3-linked glucose residues were detected. As treatment with β -mannanase significantly reduced elicitor activity, mixed-linkage (1 → 4), (1 → 6)-mannosyl residues appeared to be important for elicitor activity. The B. graminis elicitor induced the expression of all defence-related genes tested in wheat and also induced resistance to subsequent attack by B. graminis f. sp. tritici. In contrast, a hypersensitive response was not induced by the elicitor in the absence or the presence of a challenging inoculum of B. graminis f. sp. tritici. The elicitor also induced the accumulation of thaumatin-like proteins in barley, oat, rye, rice and maize, but did not induce necrosis in any of these species. This suggests that the B. graminis elicitor represents a host non-specific determinant of non-self recognition in cereals activating general defence responses other than the hypersensitive reaction.     

Correlation between sensitivity of barley to Pyrenophora teres toxins and susceptibility to the fungus

Detached leaves of 25 barleys, ranging from highly susceptible to highly resistant to Pyrenophora teres f. teres and Pyrenophora teres f. maculata, were tested for their reaction to three phytotoxins isolated from cultures of the fungus: toxin A [ L, L - N -(2-amino-2-carboxyethyl)aspartic acid], toxin C (aspergillomarasmine A) and toxin B (anhydroaspergillomarasmine A). 0.75 m M toxin A caused mainly dark yellow chlorotic symptoms but little necrosis, whereas leaves treated with 0.25 m M toxin C developed distinct necrotic symptoms and zones of light yellow chlorosis. Toxin B is only weakly toxic, and toxin B and control solutions containing aspartic acid in the concentration of 0.75 m M did not cause any symptoms. The best differentiation between the barleys was obtained by scoring chlorosis after 120 h, and the optimal toxin concentrations for this differentiation were 0.75 m M toxin A and 0.25 m M toxin C, respectively. Results with different toxin concentrations inducing distinct variation in symptom expression indicate that the two toxins have different potencies as phytotoxins. The reaction of the barleys to toxins A and C correlated well with their reaction to infection by P. teres f. teres and P. teres f. maculata, suggesting that toxins A and C may be used to select resistant barley lines in the early stages of a breeding programme.     

In vivo growth and pathotoxin production by the maize pathogen Cochliobolus carbonum

Conidia of Cochliobolus carbonum secrete a toxin (HC-toxin) during appressorium formation on maize leaves. Plasma desorption mass spectrometry revealed that approximately 70 ng of toxin per 10⁶ conidia were secreted during the first 16 h of morphogenesis. Growth of the fungus was monitored microscopically. Extensive fungal growth occurred in the susceptible interaction by 24 h. In spite of a substantial amount of HC-toxin, the fungus failed to become established in the resistant host even after 36 h. Results suggest that the resistance conditioned by Hm1, which encodes a toxin reductase, causes inactivation of the toxin early in the interaction.     

Being exposed to low concentrations of pirimiphos-methyl and chlorfenapyr has detrimental effects on the mobility of Trogoderma granarium

BACKGROUND

Sublethal effects of insecticides may negatively affect several biological and behavioral traits of insects. The lethal effects of pirimiphos-methyl and chlorfenapyr have been previously showed on Trogoderma granarium, but little knowledge is available about their sublethal effects at low concentrations on both sexes. Herein, the sublethal effects of pirimiphos-methyl and chlorfenapyr on the mobility of T. granarium males and females were investigated.

RESULTS

Lethal concentration (LC) values of pirimiphos-methyl and chlorfenapyr were lower for T. granarium females than males. LC values on males were LC₁₀ = 0.000788 and 0.00139 mg active ingredient (a.i.) cm⁻², LC₃₀ = 0.00350 and 0.00535 mg a.i. cm⁻², and LC₅₀ = 0.00986 and 0.0136 mg a.i. cm⁻² for pirimiphos-methyl and chlorfenapyr respectively. LC on females were LC₁₀ = 0.000704 and 0.00110 mg a.i. cm⁻², LC₃₀ = 0.00323 and 0.00428 mg a.i. cm⁻², and LC₅₀ = 0.00925 and 0.0110 mg a.i. cm⁻² for pirimiphos-methyl and chlorfenapyr respectively. The walking duration of beetles exposed to LC₃₀ of pirimiphos-methyl was significantly lower than the individuals exposed to LC₁₀ and LC₃₀ of both insecticides and control ones. Pirimiphos-methyl LC₃₀-exposed males remained more time on their back (101.7 s) than females (46.9 s), while the latter stayed immobile longer than males (381.7 s versus 371.9 s). The highest speed was recorded for control beetles (14.17 mm s⁻¹ females vs. 12.44 mm s⁻¹ males), while the lowest speed was observed in pirimiphos-methyl LC₃₀-treated males (8.36 mm s⁻¹) and females (9.66 mm s⁻¹).

CONCLUSIONS

Overall, males and females exposed to low concentrations of pirimiphos-methyl and chlorfenapyr showed reduced motility. This knowledge can be exploited further to unlock behavioral effects of insecticides for effective pest management programs in warehouses. © 2023 Society of Chemical Industry.     

Effect of E-cinnamaldehyde against Sclerotinia sclerotiorum on potato and induction of glutathione S-transferase genes

This research was carried out to assess the effect of E-cinnamaldehyde (EC) against Sclerotinia sclerotiorum, causal agent of potato white mold, under invivo and invitro conditions. Based on the results, EC was able to completely inhibit (P < 0.05) mycelial growth of four isolates in both volatile and contact phases after five days of inoculation at the concentrations 500 μl and 5 μl/ml, respectively. Moreover EC at concentrations 30 and 50 μl EC/ml sterile distilled water significantly reduced white mold on six potato cultivars including Pashandi, Istambouli, Agria, Marfauna, Alpha and Spartaan in greenhouse trials. In next step, induction of glutathione S-transferase (GST)-like genes identified from the pathogen (isolate 3) genome was assessed. After 2 h of exposure to both EC and cinnamom extract, four genes with locus numbers SS1G_07319.1, SS1G_07195.1, SS1G_00703.1 and SS1G_01918.1 were up-regulated. Furthermore, EC and cinnamon extract appeared to have no effect on gene expression in SS1G_10295.1. In this study, enzyme activity of GST was determined with 1-chloro-2, 4-dinitrobenzene as substrate. While enzymatic activity was 42.3 and 45.6 units mg⁻¹ protein in sterilized distilled water and ethyl acetate, respectively, it was recorded as 78.9 and 86.4 units mg⁻¹ protein for cinnamon extract and EC, respectively.