[Characterization of hydrolytic metabolism of malathion with Musca domestica by gas chromatography with nitrogen-phosphorus detector].

To examine the hydrolytic metabolism and related resistance of housefly Musca domestica (M. domestica) to malathion, differences in the hydrolytic metabolic abilities between malathion-susceptible and malathion-resistant M. domestica were examined using gas chromatography with nitrogen-phosphorus detector (GC-NPD). After incubation of M. domestica abdomen homogenates with malathion, the malathion residue was quantitatively determined by GC-NPD after extraction with a mixture of ethyl acetate and n-hexane at 2:1 (v/v). The hydrolytic metabolic abilities of M. domestica to malathion were then characterized. By comparing the differences in hydrolytic abilities between malathion-susceptible and malathion-resistant M. domestica, it was found that the hydrolytic abilities of malathion-resistant M. domestica were 6.68-fold than that of malathion-susceptible M. domestica, while the hydrolytic abilities toward α-naphthyl acetate were 1.39-fold. Resistance to malathion is related to the enhanced hydrolytic metabolism of malathion by M. domestica. Further understanding of the metabolic resistance mechanism will assist in developing a management strategy for malathion-resistant M. domestica. This method could be used for studying the metabolic ability and related resistance of M. domestica toward malathion.

Innate positive chemotaxis to pollen from crops and banker plants in predaceous biological control agents: towards new field lures?

Predator-prey interactions form the core of biological control of arthropod pests. Which tools can be used to monitor and collect carnivorous arthropods in natural habitats and targeted crops? Eco-friendly and effective field lures are urgently needed. In this research, we carried out olfactometer experiments assess innate positive chemotaxis to pollen of seven crop and banker plant by two important predatory biological control agents: the coccinellid Propylea japonica (Thunberg) and the anthocorid Orius sauteri (Poppius). We compared the attractiveness of pollens from crops and banker plants to that of common prey homogenates (aphids and thrips, respectively). Attractiveness of the tested odor sources was checked via field trapping experiments conducted in organic apple orchards and by release-recapture assays in organic greenhouse tomato crops. Maize and canola pollen were attractive to both P. japonica and O. sauteri, in laboratory and field assays. P. japonica was highly attracted by balm mint pollen, whereas O. sauteri was attracted by alfalfa pollen. Our results encourage the use of pollen from crops and banker plants as low-cost and eco-friendly attractors to enhance the monitoring and attraction of arthropod predators in biological control programs.

Cloning, characterisation and expression profiling of the cDNA encoding the ryanodine receptor in diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae).

BACKGROUND: The rynodine receptors (RyRs) are the main targets of diamide insecticides such as chlorantraniliprole. To provide the basis for a good understanding of the molecular mechanisms of diamide insecticide resistance, an RyR gene from Plutella xylostella was cloned and characterised in the present paper. RESULTS: A full-length cDNA sequence of RyR was cloned from P. xylostella through RT-PCR and rapid amplification of cDNA ends (RACE). The gene (named PxRyR1) is 15 753 bp long, with an open reading frame of 15 354 bp, encoding a predicted RyR of 5117 amino acids. An alternative splicing of the PxRyR1 was also cloned and named PxRyR2. The PxRyR1 shares 77-93% identity with other insect RyRs. Quantitative real-time PCR analysis showed that the PxRyR was expressed at a high level in second-instar larvae and adults, at a low level in prepupae and pupae and abundantly in the body wall muscle and head (respectively 6.00 and 3.12 times the expression in the gut). Western blot analysis with anti-RyR antibodies showed that the RyR was mainly present in the body wall muscle and head, but barely present in the haemocyte and gut. CONCLUSIONS: There are at least two alternative splices of PxRyR expressed in all developmental stages and tissues in P. xylostella at various levels. The results provided the basis for further understanding of the mechanisms of resistance to diamide insecticides in P. xylostella.

Electrophysiological and behavioral responses of Microplitis mediator (Hymenoptera: Braconidae) to caterpillar-induced volatiles from cotton.

Microplitis mediator Haliday (Hymenoptera: Braconidae) is an important larval endoparasitoid of various lepidopteran pests, including Helicoverpa armigera (Hübner). In China, H. armigera is a key pest of cotton and is currently the focus of several biological control efforts that use M. mediator as principal natural enemy of this pest. To improve the success of biological control efforts, behavioral studies are needed that shed light on the interaction between M. mediator and H. armigera. In this study, we determined M. mediator response to volatile compounds from undamaged, mechanically injured, or H. armigera--damaged plants and identified attractive volatiles. In Y-tube olfactometer assays, we found that mechanically damaged plants and/or plants treated with H. armigera oral secretions did not attract wasps. However, volatiles from H. armigera-damaged plants elicited a strong attraction of both M. mediator sexes. Headspace extracts from H. armigera-damaged cotton were analyzed by coupled gas chromatography-electroantennographic detection (GC-EAD), and a total of seven different compounds were found to elicit electroantennogram (EAG) responses, including an unknown compound. Six different EAD-active volatiles were identified from caterpillar-damaged cotton plants, of which 3, 7-dimethyl-1, 3, 6-octatriene and (Z)-3-hexenyl acetate were the principal compounds. Olfactometer assays indicated that individual synthetic compounds of 3, 7-dimethyl-1, 3, 6-octatriene, (Z)-3-hexenyl acetate, and nonanal were attractive to M. mediator. Field cage studies showed that parasitism of H. armigera larvae by M. mediator was higher on cotton plants to which 3,7-dimethyl-1,3, 6-octatriene was applied. Our results show that the combination of terpenoids and green leaf volatiles may not only facilitate host, mate, or food location but may also increase H. armigera parasitism by M. mediator.

Chemical composition and in vitro antimicrobial activity of the volatile oils from Gliomastix murorum and Pichia guilliermondii, two endophytic fungi in Paris polyphylla var. yunnanensis.

Volatile oils were obtained by hydro-distillation from Gliomastix murorum and Pichia guilliermondii, two endophytic fungi isolated from the traditional Chinese medicinal herb Paris polyphylla var. yunnanensis. The oils were analyzed for their chemical composition by gas chromatography-mass spectrometry (GC-MS). Palmitic acid (15.5%), (E)-9-octadecenoic acid (11.6%), 6-pentyl-5,6-dihydropyran-2-one (9.7%), and (7Z,10Z)-7,10- hexadecadienoic acid (8.3%) were the major compounds of the 40 identified components in G. murorum volatile oil. 1,1,3a,7-Tetramethyl-1a,2,3,3a,4,5,6,7b-octahydro-1H-cyclopropa[a]- naphthalene (25.9%), palmitic acid (15.5%), 1-methyl-2,4-di- (prop-1-en-2-yl)-1- vinylcyclohexane (7.9%), (E)-9-octadecenoic acid (7.3%), and (9E,12E)-ethyl-9,12-octadecadienoate (5.2%) were the major compounds of the 27 identified components in P. guilliermondii volatile oil. The in vitro antimicrobial activity of the volatile oils was also investigated to evaluate their efficacy against six bacteria and one phytopathogenic fungus. The minimum inhibitory concentration (MIC) values of the volatile oils against the test bacteria ranged from 0.20 mg/mL to 1.50 mg/mL. One of the most sensitive bacteria was Xanthomonas vesicatoria with an MIC of 0.20 mg/mL and 0.40 mg/mL for G. murorum and P. guilliermondii, respectively. The mean inhibitory concentration (IC50) of the volatile oils against spore germination of Magnaporthe oryzae was 0.84 mg/mL for G. murorum and 1.56 mg/mL for P. guilliermondii. These results indicated that the volatile oils from the endophytic fungi have strong antimicrobial activity and could be a potential source of antimicrobial ingredients.

Carboxylesterase activity, cDNA sequence, and gene expression in malathion susceptible and resistant strains of the cotton aphid, Aphis gossypii.

Levels of insecticide resistance, carboxylesterase activity, carboxylesterase expression, and the cDNA sequence of carboxylesterase gene were investigated in malathion resistant and susceptible strains of cotton aphids, Aphis gossypii (Glover). The resistant strain (MRR) exhibited 80.6-fold resistance to malathion compared to the susceptible strain (MSS) in cotton aphids. Five substrates, alpha-naphthyl acetate (alpha-NA), beta-naphthyl acetate (beta-NA), alpha-naphthyl propionate (alpha-NPr), alpha-naphthyl butyrate (alpha-NB), alpha-naphthyl caprylate (alpha-NC) and S-methyl thiobutyrate (S-MTB) were used to determine carboxylesterase activity in MRR and MSS strains of cotton aphids. Carboxylesterase activity was significantly higher in MRR strain than in MSS strain, 3.7-fold for alpha-NA, 3.0-fold for beta-NA, 2.0-fold for alpha-NPr, 2.9-fold for alpha-NB and 1.6-fold for alpha-NC, While for S-MTB, there was nearly no difference between the two strains. Two site mutations (K14Q and N354D) with high frequency were also found by sequence analysis in the MRR strain, compared with the MSS strain. The levels of gene expression for carboxylesterase of both MRR and MSS strains were determined by real-time quantitative PCRs. Compared with the MSS strain, the relative transcription levels and gene copy numbers of the carboxylesterase were 1.99- and 4.42-fold in the MRR strain, respectively. These results indicated that the increased expression of the carboxylesterase resulted from the increased transcription levels of carboxylesterase mRNA and gene copy numbers and combined with the site mutants might play role in cotton aphid resistance to malathion.