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

• Main Authors: Guoping Zhan, Jupeng Zhao, Fuhuan Ma, Bo Liu, Yong Zhong, Zijiao Song, Qingying Zhao, Naizhong Chen, Chen Ma
• Format: Article
• Language: English
• Published: MDPI AG 2020-08-01
• Series: Insects
• Subjects: <i>Bactrocera dorsalis</i>; radioprotective effects; critical threshold; low-oxygen radiation
• Online Access: https://www.mdpi.com/2075-4450/11/8/526

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 <i>Bactrocera dorsalis</i> (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 <i>B. dorsalis</i> 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.