Radiation biology of a serious tropical pigeon pea pest, <i>Maruca vitrata</i> (Fabricius) (Lepidoptera: Crambidae) and potential of radiation mediated ‘inherited (F₁) sterility technique’ for the pest suppression

Purpose: The impact of gamma radiation on the reproductive biology of the spotted pod borer, Maruca vitrata (Fabr.) (Lepidoptera: Crambidae) was ascertained to explore the potential of the radio-genetic ‘Inherited (F1) Sterility’ technique (modified Sterile Insect technique) to control this serious pigeonpea pest in India. Materials and methods: Radio-biological investigations involved dose–response studies, at a range of 100–250 Gy, with respect to radiation induced adverse effects on reproductive behavior in substerilized parent (P1) moths, inheritance of sterility and associated metamorphic disruption in F1 progeny. The reproductive competence of P1 male moths and their F1 progeny was evaluated by ascertaining the survival, mating success, sperm transfer and amphimixis of gametes from irradiated male parents and their F1 progeny. Daily ovipositional and egg fertility profile were evaluated as crucial parameters for simulation modeling for this radio-genetic technique. Results: Radiation-induced check in insemination rate and sterility in P1 and F1 generation had a positive correlation with gamma dose. The metamorphic adverse effects in F1 progeny of substerilized P1 males were influenced by P1 irradiation. A higher dose of 200 Gy that resulted in 21.1% fertility in parent cross (P1♂x N♀) could form only 14.4% F1 adults that were all malformed. A gamma dose of 150 Gy (administered to P1 males) could be considered as a suitable dose for F1 sterility, that induced 57.4% control of reproduction in parent generation, followed by 72–85% control of reproduction in F1 progeny involved in three crosses -F1♂xN♀, N♂xF1♀, F1♂xF1♀. Daily fertility profile of the eggs laid indicated a marked reduction on 4th day onwards during the ovipositional span in P1 and F1 generation. High degree of mating competitiveness value (CV) was noticed for 150 Gy irradiated male P1 moths (0.78–0.93), and their F1 male progeny (0.70–0.89), released in different sex ratios in the field cages having untreated moths. Reduced relative damage to the pigeon pea plants by the released F1 progeny in the field cages was observed in comparison to control. Conclusion: The present study indicated the potential use of a dose of 150 Gy to apply the ‘F1 sterility’ technique for parabiological suppression of the pigeon pea pod borer. The present findings and reproductive performance of the irradiated moths in F2 generation along with other compatible biorational pest control tactics (that are in progress), might help in formulating an effective integrated pest management module, including the F1 sterility technique as an integral component.研究目的：本研究旨在明确γ射线（gamma radiation）对斑荚螟（spotted pod borer，*Maruca vitrata*（Fabr.），鳞翅目（Lepidoptera）、螟蛾科（Crambidae））生殖生物学的影响，以探索放射遗传‘遗传（F1）不育’技术（radio-genetic ‘Inherited (F1) Sterility’ technique，改良型不育昆虫技术（modified Sterile Insect technique））防控印度地区这一重大木豆（pigeonpea）害虫的应用潜力。 材料与方法：本放射生物学研究设置100~250Gy的剂量梯度，开展剂量-反应研究，以探究辐射对亚不育亲代（P1）成虫生殖行为的负面影响、不育性的遗传特性，以及F1子代的相关变态畸形情况。通过检测受辐照亲代雄性成虫及其F1子代的存活能力、交配成功率、精子转移与配子融合情况，评估P1雄性成虫及其F1子代的生殖能力。以每日产卵动态与卵育性特征作为该放射遗传技术模拟建模的关键参数。 研究结果：γ射线辐照对P1代与F1代的授精率与不育性的抑制作用与辐照剂量呈正相关。亚不育P1雄性成虫的F1子代所出现的变态畸形不良反应，受亲代辐照处理的影响。当辐照剂量为200Gy时，亲代杂交组合（P1♂×未处理雌性N♀）的卵育性仅为21.1%，且其子代仅14.4%能羽化为成虫，且全部表现为畸形。针对F1不育防控而言，150Gy的辐照剂量（施加于P1雄性成虫）被认为是适宜剂量：该剂量可使亲代的生殖能力受到57.4%的抑制，随后针对F1子代的3种杂交组合——F1♂×N♀、N♂×F1♀、F1♂×F1♀，可实现72%~85%的生殖抑制效果。产卵期内的每日卵育性特征显示，P1代与F1代的卵育性在产卵第4天起出现显著下降。在设置不同性比且含有未处理成虫的田间笼室中，经150Gy辐照的P1雄性成虫（交配竞争值CV为0.78~0.93）及其F1雄性子代（交配竞争值CV为0.70~0.89）均表现出较高的交配竞争力。与对照组相比，田间笼室中释放的F1子代对木豆植株的相对为害程度显著降低。 研究结论：本研究表明，采用150Gy辐照剂量的‘F1不育’技术可用于木豆荚螟的半生物防治。本研究结果、受辐照成虫的F2代生殖表现，以及正在开展的其他兼容型生物合理害虫防控策略，将有助于构建一套有效的害虫综合治理方案，其中‘F1不育’技术可作为核心组成部分。