Development and Metabolomic Profiles of Bactrocera dorsalis (Diptera: Tephritidae) Larvae Exposed to Phytosanitary Irradiation Dose in Hypoxic Environment Using DI-SPME-GC/MS.

X-ray irradiation and modified atmospheres (MAs) provide eco-friendly, chemical-free methods for pest management. Although a low-oxygen atmospheric treatment improves the performance of some irradiated insects, its influence on the irradiation of quarantine insects and its impacts on pest control efficacy have yet to be investigated. Based on bioassay results, this study employed direct immersion solid-phase microextraction (DI-SPME) combined with gas chromatography-mass spectrometry (GC-MS) to determine metabolic profiles of late third-instar B. dorsalis larvae under normoxia (CON, Air), hypoxia (95% N2 + 5% O2, HY), super-hypoxia (99.5% N2 + 0.5% O2, Sup-HY), irradiation-alone (116 Gy, IR-alone), hypoxia + irradiation (HY + IR) and super-hypoxia + irradiation (Sup-HY + IR). Our findings reveal that, compared to the IR-alone group, the IR treatment under HY and Sup-HY (HY + IR and Sup-HY + IR) increases the larval pupation of B. dorsalis, and weakens the delaying effect of IR on the larval developmental stage. However, these 3 groups further hinder adult emergence under the phytosanitary IR dose of 116 Gy. Moreover, all IR-treated groups, including IR-alone, HY + IR, and Sup-HY + IR, lead to insect death as a coarctate larvae or pupae. Pathway analysis identified changed metabolic pathways across treatment groups. Specifically, changes in lipid metabolism-related pathways were observed: 3 in HY vs. CON, 2 in Sup-HY vs. CON, and 5 each in IR-alone vs. CON, HY + IR vs. CON, and Sup-HY + IR vs. CON. The treatments of IR-alone, HY + IR, and Sup-HY + IR induce comparable modifications in metabolic pathways. However, in the HY + IR, and Sup-HY + IR groups, the third-instar larvae of B. dorsalis demonstrate significantly fewer changes. Our research suggests that a low-oxygen environment (HY and Sup-HY) might enhance the radiation tolerance in B. dorsalis larvae by stabilizing lipid metabolism pathways at biologically feasible levels. Additionally, our findings indicate that the current phytosanitary IR dose contributes to the effective management of B. dorsalis, without being influenced by radioprotective effects. These results hold significant importance for understanding the biological effects of radiation on B. dorsalis and for developing IR-specific regulatory guidelines under MA environments.

Comparative Analysis of the Metabolic Profiles of Strains of Tribolium castaneum (Herbst) Adults with Different Levels of Phosphine Resistance Based on Direct Immersion Solid-Phase Microextraction and Gas Chromatography-Mass Spectrometry.

The management of phosphine (PH3) resistance in stored grain pests is an essential component of implementing timely and effective pest control strategies. The prevailing standard method for PH3 resistance testing involves the exposure of adult insects to a specific concentration over a fixed period. Although it is widely adopted, this method necessitates an extensive period for assay preparation and diagnosis. To address this issue, this study employed Direct Immersion Solid-Phase Microextraction (DI-SPME) coupled with Gas Chromatography-Mass Spectrometry (GC-MS) to compare and analyze the metabolic profiles of PH3-sensitive (TC-S), PH3 weak-resistant (TC-W), and PH3 strong-resistant (TC-SR) Tribolium castaneum (Herbst) adults. A total of 36 metabolites were identified from 3 different PH3-resistant strains of T. castaneum; 29 metabolites were found to present significant differences (p < 0.05) across these groups, with hydrocarbon and aromatic compounds being particularly prevalent. Seven metabolites showed no significant variations among the strains, consisting of four hydrocarbon compounds, two iodo-hydrocarbon compounds, and one alcohol compound. Further multivariate statistical analysis revealed a total of three, two, and nine differentially regulated metabolites between the TC-S versus TC-W, TC-S versus TC-SR, and TC-W versus TC-SR groups, respectively. Primarily, these metabolites comprised hydrocarbons and iodo-hydrocarbons, with the majority being associated with insect cuticle metabolism. This study demonstrates that DI-SPME technology is an effective method for studying differentially expressed metabolites in T. castaneum with different levels of PH3 resistance. This approach may help to provide a better understanding of the development of insect PH3 resistance and act as a valuable reference for the establishment of rapid diagnostic techniques for insect PH3 resistance.

Comparison of fumigation efficacy of methyl bromide alone and phosphine applied either alone or simultaneously or sequentially against Bactrocera correcta in Selenicereus undatus (red pitaya) fruit.

BACKGROUND: Bactrocera correcta (Bezzi) is a significant pest of the red pitaya fruit (Selenicereus undatus). This study investigated the insecticidal effects of methyl bromide (MB) alone, phosphine (PH3 ) alone, both applied simultaneously (PH3 + MB), and PH3 application followed sequentially by MB (PH3 → MB) against B. correcta in red pitaya fruits. RESULTS: The 3rd instar larvae of B. correcta were the most tolerant to MB alone and the combined treatments, whereas eggs were the most susceptible stage. Both the PH3 + MB and PH3 → MB treatments resulted in higher mortality at all stages than MB alone, demonstrating a synergistic effect between MB and PH3 . The toxicity of the combined treatments increased with increasing PH3 concentrations, with the optimal concentration recorded being 1.42 to 2.84 g m-3 . Further probit analysis revealed that compared to the MB treatment alone, the median lethal dose values of MB in PH3 + MB and PH3 → MB treatment, were reduced to 63.73% and 66.82%, respectively. Fruit quality was not adversely affected by either of the combined treatments. CONCLUSION: This work provides robust evidence that combining MB and PH3 to control B. correcta is highly effective, especially the PH3 → MB treatment. This combination decreased the amount of MB required for effective control at all life stages, while protecting fruit quality against MB phytotoxicity to a greater extent than conventional MB fumigation alone. © 2023 Society of Chemical Industry.

Correlation between Irradiation Treatment and Metabolite Changes in Bactrocera dorsalis (Diptera: Tephritidae) Larvae Using Solid-Phase Microextraction (SPME) Coupled with Gas Chromatography-Mass Spectrometry (GC-MS).

The metabolites produced by the larvae of Bactrocera dorsalis (Diptera: Tephritidae) exposed to different doses of irradiation were analyzed using solid phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS), and a metabonomic analysis method of irradiated insects based on GC-MS was established. The analysis revealed 67 peaks, of which 23 peaks were identified. The metabolites produced by larvae treated with different irradiation doses were compared by multivariate statistical analysis, and eight differential metabolites were selected. Irradiation seriously influenced the fatty acid metabolic pathway in larvae. Using the R platform combined with the method of multivariate statistical analysis, changes to metabolite production under four irradiation doses given to B. dorsalis larvae were described. Differential metabolites of B. dorsalis larvae carried chemical signatures that indicated irradiation dose, and this method is expected to provide a reference for the detection of irradiated insects.

Evaluation of Reference Genes for Quantitative Reverse Transcription Polymerase Chain Reaction in Bactrocera dorsalis (Diptera: Tephritidae) Subjected to Various Phytosanitary Treatments.

Bactrocera dorsalis is a major pest that causes serious damage to many fruits. Although phytosanitary treatment methods have been developed for Bactrocera control, there is a lack of information related to the gene expression pattern of B. dorsalis subjected to phytosanitary treatment conditions. Prior to quantitative reverse transcription polymerase chain reaction analysis of the most stable reference genes in B. dorsalis (Diptera: Tephritidae), B. dorsalis third-instar larvae were exposed to various phytosanitary treatments; seven candidate reference genes (18S, G6PDH, GAPDH, RPL-13, RPL-32, RPS-3, and α-Tub) were amplified and their expression stabilities were evaluated using geNorm, NormFinder, BestKeeper, and RefFinder algorithms. Different reference genes were found under different stress conditions. G6PDH was the most stable gene after heat treatment. After cold treatment, α-Tub exhibited the highest expression stability. G6PDH expression stability was the highest after fumigation with methyl bromide. RPL-32 showed the highest expression stability after irradiation treatment. Collectively, RefFinder analysis results revealed G6PDH and RPL-32 as the most suitable genes for analyzing phytosanitary treatment in B. dorsalis. This study provides an experimental basis for further gene expression analyses in B. dorsalis subjected to various phytosanitary treatments, which can aid in the development of novel phytosanitary treatments against insect pests.

Postharvest treatment of mandarin fruit using a combination of methyl bromide and phosphine against Bactrocera dorsalis (Diptera: Tephritidae).

BACKGROUND: Chinese Nanfeng mandarin (Citrus reticulate Blanco '2-6') fruit is host to the oriental fruit fly Bactrocera dorsalis Hendel, and therefore requires phytosanitary treatment before exporting abroad. The use of methyl bromide (MB) should be reduced because it has phytotoxic and ozone depleting properties. In the present study, fumigations with mixtures of gaseous phosphine (PH3 ) and MB were conducted to disinfest B. dorsalis. The effect of combined fumigation on postharvest quality of Nanfeng mandarin fruit was then evaluated. RESULTS: There was a clear synergistic effect between MB and PH3 against B. dorsalis at 20 °C. The third-instar larvae of B. dorsalis were the most tolerant to treatment with both MB alone and combined with PH3 . Toxicity assay of third instars indicated that higher PH3 concentrations increased MB toxicity, and 1.42-2.84 g m-3 of PH3 was optimal when combined with MB. Probit analysis showed that, combined with 2.13 g m-3 PH3 , similar mortality was achieved with 50% of the MB required when applied alone. Furthermore, the fruit quality test showed that MB fumigation resulted in a higher respiration rate and >40% fruit rot after storage. The combined treatment reduced these effects and did not have adverse effects on fruit firmness, soluble solid content, titratable acidity, or vitamin C content. CONCLUSION: Our findings demonstrate the synergistic effect between PH3 and MB and indicate that this treatment has potential as a novel strategy for postharvest control of B. dorsalis, especially in MB-sensitive fruit. © 2019 Society of Chemical Industry.

Evaluation of Low-Temperature Phosphine Fumigation for Control of Oriental Fruit Fly in Loquat Fruit.

Oriental fruit fly, Bactrocera dorsalis (Hendel; Diptera: Tephritidae), is recognized as a quarantine pest and a threat to Chinese loquat (Eriobotrya japonica Lindl.) fruit exports. Since loquat fruit is very sensitive to methyl bromide (MB) fumigation and cold treatment, in this study, low-temperature phosphine (PH3) fumigation was investigated to develop an alternative phytosanitary treatment method. Tolerance tests showed that the third instar was the most tolerant of all life stages of B dorsalis to PH3 gas at 8°C. Toxicity assay with 500-3000 ppm PH3 and subsequent probit analysis showed that 2000 ppm PH3 was optimal for fumigation and 152.75 h of treatment duration were required to achieve 99.9968% mortality. In the verification test, 144 and 168 h of treatment duration with 2000 ppm PH3 completely killed 35,277 and 35,134 B. dorsalis third instars, respectively. However, 13 live larvae were found after 120 h of treatment. Furthermore, these treatments reduced fruit respiration rates while causing no adverse effects on other fruit quality parameters, including firmness, soluble solid content, and titratable acidity over 192 h storage at 8°C. The results strongly suggest that low-temperature PH3 fumigation could be used for the postharvest control of B. dorsalis in loquat fruit.

Phosphine inhibits transcription of the catalase gene through the DRE/DREF system in Drosophila melanogaster.

Phosphine (PH3) is a toxin commonly used for pest control. Its toxicity is attributed primarily to its ability to induce oxidative damage. Our previous work showed that phosphine could disrupt the cell antioxidant defence system by inhibiting expression of the catalase gene in Drosophila melanogaster (DmCAT). However, the exact mechanism of this inhibition remains unclear. Here, we implemented a luciferase reporter assay driven by the DmCAT promoter in D. melanogaster S2 cells and showed that this reporter could be inhibited by phosphine treatment. A minimal fragment of the promoter (-94 to 0 bp), which contained a DNA replication-related element (DRE) consensus motif (-78 to -85 bp), was sufficient for phosphine-mediated reporter inhibition, suggesting the involvement of the transcription factor DREF. Furthermore, phosphine treatment led to a reduction in DREF expression and consequent repression of DmCAT transcription. Our results provide new insights on the molecular mechanism of phosphine-mediated catalase inhibition. Phosphine treatment leads to reduced levels of the transcription factor DREF, a positive regulator of the DmCAT gene, thereby resulting in the repression of DmCAT at transcriptional level.

Toxicity of phosphine fumigation against Bactrocera tau at low temperature.

Bactrocera tau (Walker) is one of the most harmful pests to fruits and vegetables. To counteract this pest, the development of phytosanitary treatment is required to comply with the pest regulation requirements of certain countries. This study investigated the toxicity of phosphine fumigation against B. tau under low temperature conditions. Different growth stages (eggs and instars) of B. tau were exposed to 1.07 mg/liter phosphine for 1-10 d at 5 degrees C, and compared with unfumigated flies at 5 degrees C. The results showed that tolerance to cold treatment alone or phosphine fumigation at low temperatures generally increased with the stage of insect development. However, eggs incubated for 12 h at 25 degrees C represented the most tolerant growth stage to phosphine fumigation at 5 degrees C. Furthermore, 8.56- to 2.18-d exposure periods were required to achieve 99% mortality with a range of phosphine concentrations from 0.46 to 3.81 mg/liter. C0.62 t = k expression was obtained from the LT99 values, indicating that the exposure time was more important than the phosphine concentration.

Proteomic analysis of peach fruit moth larvae treated with phosphine.

Phosphine has been used worldwide for the control of stored-product insects for many years. However, the molecular mechanism of its toxicity is not clearly understood. In the current study, larvae of the peach fruit moth were fumigated with phosphine. Proteomic analysis was then performed to identify the regulated proteins. Our results confirmed the phosphine toxicity on the peach fruit moth. The median lethal time LT50 was 38.5 h at 330 ppm at 25 degrees C. During fumigation, the respiration of the peach fruit moth was extremely inhibited. Of the 26 regulated proteins, 16 were identified by MALDI-TOF mass spectrometry after a 24 h treatment. The proteins were classified as related to metabolism (25 %), anti-oxidation (6 %), signal transduction (38 %), or defense (19 %). The rest (13 %) were unclassified. Phosphine regulation of ATP and glutathione contents, as well as of ATP synthase and glutathione S-transferase 2 activities were confirmed by enzyme activity analysis. These results demonstrate that complex transcriptional regulations underlie phosphine fumigation. New theories on the mechanism of phosphine toxicity may also be established based on these results.

[Plain radiograph and CT features of 112 patients with SARS in acute stage].

OBJECTIVE: To retrospectively analyze the X-ray and CT features of patients with suggestive of SARS at the early stages. METHODS: The study comprised 112 patients (43 men, 69 women; aged from 16 to 82 year) with clinically proved SARS. Chest radiograph was performed in all the patients and CT of thorax in 22 patients during the first week of the onset. RESULTS: In the early stage, the most common findings were patchy ground-glass opacification (GGO) (79.5% on X-ray and 81. 8% on CT) and mixed lesions of GGO with irregular consolidation (21.4% on X-ray and 45.5% on CT) and/or granulomas (14.3% on X-ray and 27.3% on CT). A majority of lesions were located in the middle and lower field (70.9%) with peripheral distribution (69%). Other findings on CT included intralobular and interlobular septal thickening (carzy-paving pattern) (36.4%), bronchiectasis (18.2%) and small pleural effusion (22.7%). CONCLUSION: Common radiologic findings of SARS are ground-glass opacification and mixed lesions of GGO with irregular consolidation and/or granulomas and lower location and peripheral distribution.