Radioprotective Effects on Late Third-Instar Bactrocera dorsalis (Diptera: Tephritidae) Larvae in Low-Oxygen Atmospheres

Abstract

Ionizing radiation creates free radicals, the effect of which is enhanced by the presence of oxygen; a low oxygen level produces radioprotective effects for insects compared with irradiation in ambient air. Modified (controlled) atmosphere packaging is used for maintaining quality and shelf-life extension; therefore, treatment efficacy may be affected, and there is a need to determine the critical O2 levels that may cause radioprotective effects. Late third-instar Bactrocera dorsalis (Hendel) larvae were irradiated in bags filled with ambient or low-oxygen air (0%, 2%, 4%, 6%, 8% O2) and were exposed to radiation doses of 8 to 64 Gy with intervals of 8 Gy. Efficacy was measured by the prevention of adult emergence. Dose–response data on mortality (failure of adult emergence) were analyzed via two-way ANOVA (analysis of variance), ANCOVA (analysis of covariance), and probit regression. The difference in radiotolerance was only significant in 0% O2 atmospheres through two-way ANOVA; therefore, the 95% confidence limits (CLs) of lethal dose ratios at LD99 were used to determine significant differences between treatments at different O2 levels. The differences in radiotolerance were significant in 0% and 2% O2 but insignificant in 4%, 6%, and 8% O2 environments when compared with radiation in ambient air. The critical threshold of radioprotective effects for late third-instar B. dorsalis larvae is an O2 level of ≥4% and <6%, but a maximum radiation dose of 14 Gy can compensate for this effect during phytosanitary irradiation treatment.

Combination of Modified Atmosphere and Irradiation for the Phytosanitary Disinfestation of Trogoderma granarium Everts (Coleoptera: Dermestidae)

“…There is a potential for this treatment schedule to be used for the phytosanitary treatment of infested commodity on sea container, warehouse, MAP, or railway cabins, for example, the China-Europe Railway Express which takes two weeks or more [ 54 ]. A low-oxygen atmosphere may reduce the radiation effects [ 16 , 22 , 35 , 38 , 65 ]. The procedure for the application of MA-irradiation combination treatment should be conducting irradiation at normal atmosphere, firstly, followed by MA including the controlled atmosphere.…”

“…All the MA treatments were conducted in the four-liter gastight airbags (Dalian Delin Gas Packaging Co., Ltd, Dalian, China). For each treatment, three or four plastic boxes containing the insect samples (irradiated or none) were placed into one gastight airbag through the opening (at the bottom), followed by the sealing of the airbag, exhausting all the air with a diaphragm pump, and injecting 1% or 2% O 2 (with N 2 balance) (Beijing Green Oxygen Tiangang Technology Development Co., Ltd, Beijing, China) into the airbag and kept it for a few minutes [ 38 ]. The exhausting-injecting procedure was repeated at least three times to purify the gas in the airbag.…”

“…Mortality data for irradiation, MA treatment alone or their combinations were corrected by using Abbott’s formula [ 39 ] and then subjected to two-way or three-way Analysis of Variance (ANOVA) to analyze the individual effects of main factors and their interaction effects; means (±SD, for all the mortality) were compared by Tukey’s multiple comparison tests; where DPS software was used in the analysis [ 40 ]. The dose–response (time-mortality) data on MA treatment alone or in combination with irradiation were analyzed with Probit model by using PoloPlus 2.0 program to estimate the lethal exposure time (using non-transformed exposure times), in which any mortality data between 0 and 100%, and the shortest exposure time causing 100% mortality were used in the analysis [ 38 , 41 ]. Pare-wise comparison tests were performed by calculating the 95% confidence limits (CIs) of the lethal dose ratios at LT 90 , LT 99 , and LT 99.9968 so as to compare the significance of the tolerance of the khapra beetle between larval stages and treatments at different O 2 levels.…”

“…Pare-wise comparison tests were performed by calculating the 95% confidence limits (CIs) of the lethal dose ratios at LT 90 , LT 99 , and LT 99.9968 so as to compare the significance of the tolerance of the khapra beetle between larval stages and treatments at different O 2 levels. If the 95% CIs excludes 1, then the LTx values are significantly different [ 38 , 42 , 43 ].…”

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

“…The larvae were irradiated using an RS-2000 Pro X-ray irradiator (Rad Source Technologies, Inc., Coral Springs, FL, USA) with operating parameters of 220 KV and 17.6 mA, as previously described by Zhan et al (2020) [ 33 ]. Two groups of larvae were irradiated at doses of 40 Gy and 80 Gy, respectively.…”