Feeding response of the cotton aphid,Aphis gossypii,to sublethal rates of flonicamid and imidacloprid

The cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae), is an important sap‐sucking pest of many plants, including melons and peppers. This study was conducted to determine the effects of sublethal exposure to flonicamid and imidacloprid and the mechanisms by which these insecticides affect the feeding behavior of A. gossypii. The median lethal concentrations (LC₅₀) of flonicamid and imidacloprid for adult A. gossypii were 2.40 and 1.92 mg l^?1, respectively. The lower lethal concentrations of flonicamid were 1.01 mg l^?1 (LC₃₀) and 0.29 mg l^?1 (LC₁₀), and those of imidacloprid were 0.82 mg l^?1 (LC₃₀) and 0.24 mg l^?1 (LC₁₀). The developmental period of A. gossypii nymphs at LC₃₀ was 3.6 days for both insecticides, which was shorter than that of the untreated controls (4.2 days). Longevity and total fecundity of A. gossypii adults were decreased at the sublethal concentrations of both insecticides. The lowest net reproductive rate was observed in A. gossypii treated with the LC₃₀ of flonicamid. Feeding behavior analyses using an electrical penetration graph showed that sublethal concentrations of flonicamid and imidacloprid had significant effects on the duration of phloem ingestion. Higher doses of flonicamid induced starvation by inhibiting phloem ingestion, whereas imidacloprid acted as a contact toxin rather than an inhibitor of feeding behavior.     

Systemic control efficacy of neonicotinoids seeds dressing on English grain aphid (Hemiptera: Aphididae)

English grain aphid, Sitobion avenae (Fabricius) (Hemiptera: Aphididae), is an important pest of wheat (Triticum aestivum L.), and is usually controlled by intensive foliar sprays of pesticides under field conditions. In order to reduce labour costs and increase the utilization of pesticides, neonicotinoids seed treatment was studied as a simple and accurate control technology for S. avenae. We evaluated the mortality of imidacloprid, acetamiprid, thiamethoxam, clothianidin, nitenpyram and dinotefuran to the English grain aphid by seed dressing methods in the laboratory, and found that the toxicity with that LC₅₀ of clothianidin (20.97?a.i.?g/100?kg seeds) and thiamethoxam (28.84?a.i.?g/100?kg seeds) to S. avenae are higher than other neonicotinoids. LC₅₀ values of nitenpyram, imidacloprid and acetamiprid ranged between 120?a.i.?g/100?kg seeds and 210?a.i.?g/100?kg seeds. Dinotefuran showed the lowest toxicity with LC₅₀ value 565.76?a.i.?g/100?kg seeds to English grain aphid. Field plot experiments were conducted to investigate the control efficacy of neonicotinoids seed treatment for the aphid, and the effects on growth of wheat. Field observations indicated that clothianidin and thiamethoxam provided the better control efficacy on the English grain aphid than imidacloprid, and had no influence on wheat seedling emergence. These results showed that seed treatment by neonicotinoids was effective against S. avenae throughout the growth period, furthermore, thiamethoxam and clothianidin were the effective and safe alternative options for S. avenae management in the crop.     

5种杀虫剂对滇东白背飞虱种群的毒性及其田间药效

【目的】为持续有效防控白背飞虱,研究云南东部白背飞虱种群对常用5种杀虫剂的敏感性及药剂的田间防治效果。【方法】采用室内稻茎浸渍法测定白背飞虱种群对5种杀虫剂的敏感性,同期通过田间小区试验评价5种杀虫剂对白背飞虱种群的防治效果。【结果】与敏感种群比较,噻虫嗪、噻嗪酮、吡虫啉、吡蚜酮和毒死蜱对滇东白背飞虱种群的LC_(50)分别为0.208、0.459、0.608、3.108、1.256 mg·L~(-1),抗性倍数分别为2.2、10.4、5.6、6.5、5.3倍;白背飞虱对噻虫嗪无抗性,对吡虫啉、吡蚜酮和毒死蜱为低水平抗性,对噻嗪酮为中等水平抗性;5种杀虫剂药后1、5和10 d对白背飞虱种群的田间防控效果均有显著差异。除了吡蚜酮外,其他药剂的防效均在80%以上,其中以吡虫啉和噻嗪酮的持续期较长,药后10 d仍在90%以上;噻虫嗪和吡虫啉药后1和5 d的防效达90%以上;吡蚜酮药效在供试药剂中防效最低,在64.88%～77.82%之间。【结论】滇东师宗白背飞虱种群对噻嗪酮为中等水平抗性,对吡虫啉、吡蚜酮和毒死蜱均为低水平抗性,对噻虫嗪无抗性,田间防控效果以吡虫啉和噻嗪酮为最好。建议滇东稻区可以使用吡虫啉和噻嗪酮药剂防控白背飞虱,注意控制吡蚜酮的使用次数与用量。     

Sublethal effects of imidacloprid exposure on <Emphasis Type="Italic">Spalangia endius</Emphasis>, a pupal parasitoid of filth flies

Parasitoids and neonicotinoids can both suppress economically harmful filth fly populations. However, sublethal effects of neonicotinoids have not previously been studied for commonly used species of filth fly parasitoids. Exposure to an LC₅₀ of imidacloprid decreased the ability of surviving individuals of the parasitoid wasp Spalangia endius Walker (Hymenoptera: Pteromalidae) to kill house fly pupae under some conditions. In an unburied-hosts experiment, significantly more flies and fewer parasitoids emerged in the LC₅₀ imidacloprid treatment versus the LC₁₀ or controls. Parasitoid sex ratio and longevity were not affected. However, in a buried-hosts experiment, parasitoid and fly emergence were independent of treatment. ELISA (enzyme-linked immunosorbent assay) showed lower imidacloprid residues in or on parasitoids exposed to the media in which hosts were buried. Our findings suggest that substrate may reduce pesticides on biological control agents that burrow, making them more effective.     

Can insecticide mixtures be considered to surmount neonicotinoid resistance in Bemisia tabaci?

Cotton whitefly, Bemisia tabaci is an important polyphagous pest worldwide. It is exposed to various chemical insecticides throughout the year, resulting in the rapid development of insecticide resistance. Mixtures of insecticides with distinct modes of action could enhance the toxicity of chemicals more effectively than sequences or rotations in resistant pest populations. Bioassays were conducted to study the efficacy of mixtures of neonicotinoid and ketoenol insecticides at different ratios against a laboratory susceptible (Lab-WB) and a neonicotinoid resistant (TMX-SEL) strain of B. tabaci Asia I. The results showed that mixtures of imidacloprid, acetamiprid, thiamethoxam or dinotefuran with spiromesifen at 1:1, 1:10 and 1:20 ratios and of imidacloprid, thiamethoxam or dinotefuran with spirotetramat at 1:1 ratio significantly increased (p < 0.05) toxicity to neonicotinoids in TMX-SEL strain. The combination indices of each tested neonicotinoids + ketoenols at 1:1 ratio and of acetamiprid + spiromesifen, and imidacloprid or dinotefuran + spirotetramat at 1:10 ratio for TMX-SEL strain were significantly below 1, suggesting synergistic interactions. The inhibitors PBO and DEF largely overcame resistance to the tested neonicotinoids, while none of the synergists significantly restored the susceptibility of B. tabaci to ketoenols. Increased activities of P450 monooxygenase and esterase were observed in TMX-SEL strain with an elevated 2.76 and 1.32-fold, respectively. Mixtures of neonicotinoids with spiromesifen or spirotetramat at a 1:1 ratio could be used to restore the neonicotinoid susceptibility in B. tabaci.     

Rapid induction of <Emphasis Type="Italic">Agrobacterium</Emphasis> <Emphasis Type="Italic">tumefaciens</Emphasis>-mediated transgenic roots directly from adventitious roots in <Emphasis Type="Italic">Panax</Emphasis> <Emphasis Type="Italic">ginseng</Emphasis>

Root segments from seedlings of Panax ginseng produced adventitious roots directly when cultured on 1/2 MS solid medium lacking NH₄NO₃ and containing 3.0 mg l⁻¹ IBA. Using this adventitious root formation, we developed rapid and efficient transgenic root formation directly from adventitious root segments in P. ginseng. Root segments were co-cultivated with Agrobacterium tumefaciens (GV3101) caring β-glucuronidase (GUS) gene. Putative transgenic adventitious roots were formed directly from root segments on medium with 400 mg l⁻¹ cefotaxime and 50 mg l⁻¹ kanamycin. Kanamycin resistant adventitious roots were selected and proliferated as individual lines by subculturing on medium with 300 mg l⁻¹ cefotaxime and 50 mg l⁻¹ kanamycin at two weeks subculture interval. Frequency of transient and stable expression of GUS gene was enhanced by acetosyringon (50 mg l⁻¹) treatment. Integration of transgene into the plants was confirmed by the X-gluc reaction, PCR and Southern analysis. Production of transgenic plants was achieved via somatic embryogenesis from the embryogenic callus derived from independent lines of adventitious roots. The protocol for rapid induction of transgenic adventitious roots directly from adventitious roots can be applied for a new Agrobacterium tumefaciens-mediated genetic transformation protocol in P. ginseng.     

Effects of plant growth regulators and sucrose on post harvest physiology,membrane stability and vase life of cut spikes of gladiolus

Effects of post-harvest application of two plant growth regulators viz., gibberellic acid (GA₃) and benzyl adenine (BA) with sucrose in the vase solution on cell membrane stability and vase life of gladiolus were investigated. The vase solution treatment combinations of GA₃ and BA with sucrose significantly increased the membrane stability index and enhanced the vase life as compared to the sucrose alone treatments or the controls. Vase solution treatment of GA₃ (50 mg l⁻¹), followed by BA (50 mg l⁻¹) with sucrose (50 g l⁻¹) significantly increased solution uptake, fresh weight and dry weight of cut spikes. The same treatments also enhanced the concentration of reducing and non-reducing sugars in gladioli petals 4 days after treatment (DAT). Cut spikes in vase solution enriched with 50 mg l⁻¹ GA₃ + 50 g l⁻¹ sucrose showed higher antioxidative enzyme activities of superoxide dismutase (SOD) and glutathione reductase (GR), lower lipoxygenase (LOX) activity and lipid peroxidation (measured as TBARS). Petal membrane stability index was also highest in cut spikes 6 DAT with 50 mg l⁻¹ GA₃ + 50 g l⁻¹ sucrose vase solution. Treatment of gladiolus cut spikes with 50 mg l⁻¹ GA₃ + 50 g l⁻¹ sucrose vase solution showed two fold increase in vase life and improved flower quality with a higher number of open flower per spike at any one time. These results suggest that post-harvest application of GA₃ (50 mg l⁻¹) with sucrose (50 g l⁻¹) maintains higher spike fresh and dry weight, improves anti-oxidative defence, stabilizes membrane integrity leading to a delay in petal cell death.     

High efficiency plant regeneration and genetic fidelity of regenerants by SCoT and ISSR markers in chickpea (Cicer arietinum L.)

High efficient and repeatable in vitro regeneration protocol was established from embryo axis, half-seed, axillary meristem, and cotyledonary node explants of chickpea. Various concentrations and combinations of various plant growth regulators (PGRs) were employed to induce multiple shoots, shoot elongation and rooting of shoots to obtain complete plantlets of chickpea. The pretreatment of seeds with 6-benzyl aminopurine (BAP) at 1.0 mg l^?1 was found to significantly increase the multiple shoot regeneration from the all explants tested. Among three PGRs such as BAP, kinetin (KIN) and thidiazuron (TDZ) tested for multiple shoot induction; BAP at 2.0 mg l^?1 produced the maximum number of shoots in all tested explants. The maximum number of shoots (48.80 shoots/explant) was attained from the embryo axis explant followed by half-seed (32.76 shoots/explant), axillary meristem (28.34 shoots/explant) and cotyledonary node explant (18.47 shoots/explant) on medium augmented with 2.0 mg l^?1 BAP along with 0.05 mg l^?1 Indole-3-butyric acid (IBA). The optimum percentage of shoot elongation response was recorded (96.68%) on medium fortified with IAA (0.05 mg l^?1), GA₃ (1.0 mg l^?1) and BAP (1.0 mg l^?1) with an average shoot length of 8.82 cm. The elongated shoots were successfully rooted in medium augmented with 2.0 mg l^?1 IBA. The complete plants were acclimatized in the greenhouse with a survival rate of 72%. The plantlets regenerated from four explants appeared to be morphologically similar to mother plants. The genetic fidelity of in vitro regenerated plants was evaluated using Start Codon Targeted and Inter simple sequence repeats molecular markers. The in vitro regenerated plants from all four explants were found to be the true to type with their mother plant. The in vitro protocol presented in the study should offer as a feasible system for chickpea genetic transformation.

     

<Emphasis Type="Italic">Agrobacterium</Emphasis>-mediated genetic transformation and regeneration of transgenic plants using leaf segments as explants in Valencia sweet orange

In this study, attempts were made to develop a protocol for regeneration of transgenic plants via Agrobacterium tumefaciens-mediated transformation of leaf segments from ‘Valencia’ sweet orange (Citrus sinensis L. Osbeck) using gfp (green fluorescence protein) as a vital marker. Sensitivity of the leaf segments regeneration to kanamycin was evaluated, which showed that 50 mg l⁻¹ was the best among the tested concentrations. In addition, factors affecting the frequency of transient gfp expression were optimized, including leaf age, Agrobacterium concentration, infection time, and co-cultivation period. Adventitious shoots regenerated on medium containing Murashige and Tucker basal medium plus 0.1 mg l⁻¹ α-naphthaleneacetic acid (NAA), 0.5 mg l⁻¹ 6-benzyladenine (BA) and 0.5 mg l⁻¹ kinetin (KT). The leaf segments from 3-month-old in vitro seedlings, Agrobacterium concentration at OD₆₀₀ of 0.6, 10-min immersion, and co-cultivation for 3 days yielded the highest frequency of transient gfp expression, shoots regeneration response and transformation efficiency. By applying these optimized parameters we recovered independent transformed plants at the transformation efficiency of 23.33% on selection medium (MT salts augmented with 0.5 mg l⁻¹ BA, 0.5 mg l⁻¹ KT, 0.1 mg l⁻¹ NAA, 50 mg l⁻¹ kanamycin and 250 mg l⁻¹ cefotaxime). Expression of gfp in the leaf segments and regenerated shoots was confirmed using fluorescence microscope. Polymerase chain reaction (PCR) analysis using gfp and nptII gene-specific primers further confirmed the integration of the transgene in the independent transgenic plants. The transformation methodology described here may pave the way for generating transgenic plants using leaf segments as explants.     

Bioremediation of metal contamination in the Plankenburg River,Western Cape,South Africa

Three bioreactors (two laboratory-scale and one on-site) were evaluated for their efficiency to reduce metal concentrations in water collected from the Plankenburg River, South Africa. Water (bioreactors one, two and on-site) and bioballs (bioreactors two and on-site) collected throughout the study periods were digested and analysed using Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). Aluminium (Al), nickel (Ni), and zinc (Zn) concentrations decreased from 0.41 mg l^?1 to 0.06 mg l^?1 (85%), 0.2 mg l^?1 to 0.07 mg l^?1 (65%) and 75 mg l^?1 to 0.02 mg l^?1 (97%), respectively (bioreactor one). Aluminium [(1.55–0.38 mg l^?1 (75%)], copper (Cu) [57% (from 0.33 mg l^?1 to 0.14 mg l^?1)], iron (Fe) [71.99–40.4 mg l^?1 (44%)] and manganese (Mn) [57% (0.07–0.03 mg l^?1)] concentrations also decreased in the water samples from bioreactor two. In the on-site, six-tank bioreactor system, concentrations for Fe, Cu, Mn and Ni decreased, while Zn and Al concentrations increased. The concentrations recorded in biofilm samples were higher than the corresponding water samples. The bioballs employed in the bioreactor were thus shown to be efficient attachment surfaces for biofilm development and subsequent metal accumulation. Potentially metal-tolerant organisms (Pseudomonas sp., Sphingomonas sp., and Bacillus sp.) were also identified using phylogeny.     

Differential sensitivity of honey bees and bumble bees to a dietary insecticide (imidacloprid)

Currently, there is concern about declining bee populations and the sustainability of pollination services. One potential threat to bees is the unintended impact of systemic insecticides, which are ingested by bees in the nectar and pollen from flowers of treated crops. To establish whether imidacloprid, a systemic neonicotinoid and insect neurotoxin, harms individual bees when ingested at environmentally realistic levels, we exposed adult worker bumble bees, Bombus terrestris L. (Hymenoptera: Apidae), and honey bees, Apis mellifera L. (Hymenoptera: Apidae), to dietary imidacloprid in feeder syrup at dosages between 0.08 and 125 μg l^?1. Honey bees showed no response to dietary imidacloprid on any variable that we measured (feeding, locomotion and longevity). In contrast, bumble bees progressively developed over time a dose-dependent reduction in feeding rate with declines of 10–30% in the environmentally relevant range of up to 10 μg l^?1, but neither their locomotory activity nor longevity varied with diet. To explain their differential sensitivity, we speculate that honey bees are better pre-adapted than bumble bees to feed on nectars containing synthetic alkaloids, such as imidacloprid, by virtue of their ancestral adaptation to tropical nectars in which natural alkaloids are prevalent. We emphasise that our study does not suggest that honey bee colonies are invulnerable to dietary imidacloprid under field conditions, but our findings do raise new concern about the impact of agricultural neonicotinoids on wild bumble bee populations.     

Assessment of cross-resistance potential to neonicotinoid insecticides in Bemisia tabaci (Hemiptera: Aleyrodidae)

Laboratory bioassays were carried out with four neonicotinoid insecticides on multiple strains of Bemisia tabaci (Gennadius) to evaluate resistance and cross-resistance patterns. Three imidacloprid-resistant strains and field populations from three different locations in the southwestern USA were compared in systemic uptake bioassays with acetamiprid, dinotefuran, imidacloprid and thiamethoxam. An imidacloprid-resistant strain (IM-R) with 120-fold resistance originally collected from Imperial Valley, California, did not show cross-resistance to acetamiprid, dinotefuran or thiamethoxam. The Guatemala-resistant strain (GU-R) that was also highly resistant to imidacloprid (RR=109-fold) showed low levels of cross-resistance when bioassayed with acetamiprid and thiamethoxam. However, dinotefuran was more toxic than either imidacloprid or thiamethoxam to both IM-R and GU-R strains as indicated by low LC50s. By contrast, a Q-biotype Spanish-resistant strain (SQ-R) of B. tabaci highly resistant to imidacloprid demonstrated high cross-resistance to the two related neonicotinoids. Field populations from Imperial Valley (California), Maricopa and Yuma (Arizona), showed variable susceptibility to imidacloprid (LC50s ranging from 3.39 to 115 microg ml(-1)) but did not exhibit cross-resistance to the three neonicotinoids suggesting that all three compounds would be effective in managing whiteflies. Yuma populations were the most susceptible to imidacloprid. Dinotefuran was the most toxic of the four neonicotinoids against field populations. Although differences in binding at the target site and metabolic pathways may influence the variability in cross-resistance patterns among whitefly populations, comparison of whitefly responses from various geographic regions to the four neonicotinoids indicates the importance of ecological and operational factors on development of cross-resistance to the neonicotinoids.     

Development of methods to evaluate susceptibility of soybean aphid to imidacloprid and thiamethoxam at lethal and sublethal concentrations

The soybean aphid, Aphis glycines Matsumura (Homoptera: Aphididae), is a recent introduction (2000) from Asia and has become a serious soybean [Glycine max (L.) Merr. (Fabaceae)] pest in North America. Seed treatments using the neonicotinoid insecticides, imidacloprid and thiamethoxam, have been suggested as a method of control, and the use of these insecticides is becoming widespread. As a consequence, there is increased potential to select for resistance to these compounds. In the case of soybean aphids, baseline susceptibility to neonicotinoid insecticides and standardized methods for bioassay are lacking. A bioassay technique that uses excised soybean leaves immersed in an insecticide solution was developed to determine systemic insecticidal activity at lethal and sublethal concentrations. Mortality and population growth inhibition were evaluated after 7 days. Life table parameters were calculated by exposing 1‐day‐old aphids to three concentrations of thiamethoxam. Aphid mortality and nymph production were recorded daily until the entire cohort collapsed. Soybean aphid age‐specific survivorship, fecundity, net reproductive rate, longevity, intrinsic rate of increase, discrete daily growth rate, and life expectancy were all significantly reduced at higher thiamethoxam concentrations. Soybean aphid response to both insecticides was similar, and both compounds were very toxic with LC₅₀s of 31.3 and 16.9 ng ml^?1 and EC₅₀s of 6.3 and 5.4 ng ml^?1 for imidacloprid and thiamethoxam, respectively. These results indicate that the methods developed in this study had negligible impact on the life table estimates measured and can be used to develop a baseline of susceptibility as a benchmark for subsequent resistance monitoring. Given the rapid and widespread adoption of this new insecticide class, vigilant monitoring for changes in susceptibility will be essential to its long‐term sustainability.     

Sub-lethal effects of tiametoxam on life table parameters of the cabbage aphid,Brevicoryne brassicae (L.) (Hemiptera: Aphididae) under laboratory conditions

Efficiency of tiametoxam was determined on population growth parameters of cabbage aphid, Brevicoryne brassicae L. (Hemiptera: Aphididae) using demographic toxicology by leaf spray method. At first, bioassay was performed. The LC₅₀ values and confidence limits for thiamethoxam were 169.05?ppm (92.61–342.51). To evaluate, the sub-lethal effect of this insecticide on population growth parameters of cabbage aphid, LC₂₅ and LC₁₀ concentrations of tiametoxam were used at 58.8 and 22.05?ppm, respectively. Also, the LC₅₀ value of insecticide on the life table estimates was measured. Experiments were carried out in the laboratory at 23?±?1?°C, 60?±?5% RH and 16:8 (L:D) photoperiod on cabbage seedlings, Brassica oleracea, var. capitata L. Net fecundity rate decreased in insecticide-treated populations. Intrinsic rates of increase (r_m) were lower in tiametoxam treatment than in controls. There was a relative increase in intrinsic death rates of treated populations. The mean generation time and doubling time were also lower in population treated with insecticide than the control. There was a considerable reduction in the average numbers of nymphs reproduced per female as compared with the control. The average longevity of female adults in the control was significantly different (p?<?0.05) from those treated with thiamethoxam.     

Status of Resistance of <Emphasis Type="Italic">Bemisia tabaci</Emphasis> (Hemiptera: Aleyrodidae) to Neonicotinoids in Iran and Detoxification by Cytochrome P450-Dependent Monooxygenases

Nine Bemisia tabaci (Gennadius) populations were collected from different regions of Iran. In all nine populations, only one biotype (B biotype) was detected. Susceptibilities of these populations to imidacloprid and acetamiprid were assayed. The lethal concentration 50 values (LC₅₀) for different populations showed a significant discrepancy in the susceptibility of B. tabaci to imidacloprid (3.76 to 772.06 mg l^?1) and acetamiprid (4.96 to 865 mg l^?1). The resistance ratio of the populations ranged from 9.72 to 205.20 for imidacloprid and 6.38 to 174.57 for acetamiprid. The synergistic effects of piperonylbutoxide (PBO) and S,S,S-tributylphosphorotrithioate (DEF) were evaluated for the susceptible (RF) and resistant (JR) populations for the determination of the involvement of cytochrome P450-dependent monooxygenase and carboxylesterase, respectively, in their resistance mechanisms. The results showed that PBO overcame the resistance of the JR population to both imidacloprid and acetamiprid, with synergistic ratios of 72.7 and 106.9, respectively. Carboxylesterase, glutathione S-transferase and cytochrome P450-dependent monooxygenase were studied biochemically, for the purpose of measuring the activity of the metabolizing enzymes in order to determine which enzymes are directly involved in neonicotinoid resistance. There was an increase in the activity of cytochrome P450-dependent monooxygenase up to 17-fold in the resistant JR population (RR?=?205.20). The most plausible activity of cytochrome P450-dependent monooxygenase correlated with the resistances of imidacloprid and acetamiprid, and this suggests that cytochrome P450-dependent monooxygenase is the only enzyme system responsible for neonicotinoid resistance in the nine populations of B. tabaci.     

Ethrel treatment enhanced isoflavonoids accumulation in cell suspension cultures of Pueraria tuberosa, a woody legume

The cell cultures of Pueraria tuberosa, a perennial leguminous lianas, were maintained in modified MS medium (KNO₃ 475 mg l⁻¹, thiamine 1 mg l⁻¹, biotin 1 mg l⁻¹, calcium pantothenate 1 mg l⁻¹) containing 0.1 mg l⁻¹ 2,4,5-trichloroacetic acid and 0.1 mg l⁻¹ kinetin. Isoflavonoids (puerarin, genistin, daidzein, genistein) accumulation in cell suspension cultures was increased by 14-fold to ~12 mg l⁻¹ after 48 h of adding 100 μM ethrel. Ethrel inhibitors (silver nitrate and silver thiosulfate) completely inhibited this effect in the presence of ethrel and isoflavonoids were not detected in the spent medium. The increase was dose dependent and can be explored to trigger high yield of isoflavonoids production.     

Long‐term risk assessment on noneffective and effective toxic doses of imidacloprid to honeybee workers

Imidacloprid is the most widely used insecticide in agriculture. Its impact on honeybees has received worldwide attention. Foliar sprays are commonly and frequently used for piercing insect control, particularly on cotton in southern USA. To simulate field exposures of formulated imidacloprid (Advise^® 2Fl), we used a modified spray tower to treat honeybee workers and monitored five enzyme activities and survival for up to 52 days. Results indicated that spray treatments twice a week for 52 days with 0.001 and 1 mg/L and once a week for three weeks with 4.3 mg/L Advise showed no adverse effect on bee survival, where imidacloprid‐treated bees could live as long as untreated bees. Concentration ≥80 mg/L significantly reduced bee survival, and substantial number of bees continued to die after 48‐hr of post‐treatment period which was commonly used for measuring insecticide toxicity. The body weight of imidacloprid‐treated bees (at LC₂₀ and LC₅₀) was also significantly reduced. Enzymatic data showed that activities of detoxification enzymes esterase and glutathione S‐transferase (GST), insecticide‐target enzyme acetylcholinesterase (AChE) and honey enzyme invertase in imidacloprid‐treated survivors were mostly similar to those found in untreated bees. The immunity‐related phenoloxidase (PO) activity in imidacloprid‐treated survivors was also mostly similar to that of untreated control, but higher PO activity was detected in bees treated with higher concentrations for 3 weeks. By using both bioassays and enzymatic assays, this study revealed long‐term noneffective and effective concentrations of imidacloprid that may be useful for accurate assessment of toxicity risk of neonicotinoids to bees.     

Influence of growth regulators and elicitors on cell growth and α-tocopherol and pigment productions in cell cultures of <Emphasis Type="Italic">Carthamus tinctorius</Emphasis> L.

The present study examined the effects of plant growth hormones, incubation period, biotic (Trametes versicolor, Mucor sp., Penicillium notatum, Rhizopus stolonifer, and Fusarium oxysporum) and abiotic (NaCl, MgSO₄, FeSO₄, ZnSO₄, and FeCl₃) elicitors on cell growth and α-tocopherol and pigment (red and yellow) productions in Carthamus tinctorius cell cultures. The cell growth and α-tocopherol and pigment contents improved significantly on Murashige and Skoog (MS) liquid medium containing 50.0 μM α-naphthalene acetic acid (NAA) and 2.5 μM 6-Benzyladenine (BA) at 28 days of incubation period. Incorporation of T. versicolor (50 mg l⁻¹) significantly enhanced the production of α-tocopherol (12.7-fold) and red pigment (4.24-fold). Similarly, supplementation of 30 mg l⁻¹ T. versicolor (7.54-fold) and 70 mg l⁻¹ Mucor sp. (7.40-fold) significantly increased the production of yellow pigment. Among abiotic elicitors, NaCl (50–70 mg l⁻¹) and MgSO₄ (10–30 mg l⁻¹) significantly improved production of α-tocopherol (1.24-fold) and red pigment (20-fold), whereas yellow pigment content increased considerably by all the abiotic elicitor treatments. Taken together, the present study reports improved productions of α-tocopherol and the pigment as a stress response of safflower cell cultures exposed to these elicitors.     

Photoinhibition-induced reduction in photosynthesis is alleviated by abscisic acid,cytokinin and brassinosteroid in detached tomato leaves

Detached leaves of tomato (Lycopersicon esculentum Mill.) experienced photoinhibition associated with sharp reductions in net photosynthetic rate (Pn), quantum efficiency of PSII (Φ_PSII) and photochemical quenching (qP) even though they were exposed to mild light intensity (400 μmol m⁻² s⁻¹ PPFD) at 28°C. Photoinhibition and the reduction in Pn, Φ_PSII and qP, however, were significantly alleviated by 1 mg l⁻¹ ABA, 0.1 mg l⁻¹ N-(2-chloro-4-pyridyl)-N′-phenylurea (CPPU) and 0.01 mg l⁻¹ 24-epibrassinolide (EBR). Higher concentrations, however, reduced the effects or even exacerbated the occurrence of photoinhibition. Superoxide dismutase and ascorbate peroxidase activity in leaves increased with the increases in ABA concentration within 1–100 mg l⁻¹, CPPU concentration within 0.1–10 mg l⁻¹ and EBR concentration within 0.01–1.0 mg l⁻¹. Catalase and guaiacol peroxidase activity also increased with the increase in EBR concentration but CPPU and ABA treatments at higher concentrations caused a decrease. Malondialdehyde (MDA) content decreased with the increase in CPPU concentration. ABA and EBR, however, decreased MDA concentration only at 1 and 0.01 mg l⁻¹, respectively. In conclusion, detached leaves had increased sensitivity to PSII photoinhibition. Photoinhibition-induced decrease in photosynthesis, however, was significantly alleviated by EBR, CPPU and ABA at a proper concentration.     

Fluoranthene influences endogenous abscisic acid level and primary photosynthetic processes in pea (<Emphasis Type="Italic">Pisum sativum</Emphasis> L.) plants in vitro

The influence of increasing concentrations (0.1, 1.0 and 5.0 mg l⁻¹) of fluoranthene (FLT) on growth, endogenous abscisic acid (ABA) level and primary photosynthetic processes in 21-day-old pea plants (Pisum sativum L.) in vitro was investigated. Murashige and Skoog’s (MS) medium, with or without FLT, was enriched with indole-3-acetic acid (IAA; 0.1 mg l⁻¹) or a combination of IAA (0.1 mg l⁻¹) plus N⁶-benzyladenine (BA; 0.1 mg l⁻¹). The level of endogenous ABA significantly increased with increasing FLT concentrations in the presence of both IAA and IAA plus BA. An increased level of endogenous ABA was observed in plants treated with IAA alone. The growth of shoot, callus and the content of photosynthetic pigments (chlorophyll a and b, carotenoids), in both IAA- and IAA plus BA-treated plants, were significantly stimulated by FLT at its lowest concentration (0.1 mg l⁻¹) assayed in this study. However, FLT at higher concentrations (1.0 and 5.0 mg l⁻¹) significantly inhibited all these parameters. Chlorophyll fluorescence imaging showed that FLT only at the highest concentration (5.0 mg l⁻¹) in the presence of IAA (0.1 mg l⁻¹) significantly increased F₀, but decreased F_V/F_M and Φ_II.