粘质沙雷氏菌S-JS1与5种杀虫剂对灰飞虱的联合作用及该菌对灰飞虱相关酶活性的影响

为明确粘质沙雷氏菌Serratia marcescens S-JS1与杀虫剂对灰飞虱的联合作用，以及S-JS1对灰飞虱解毒酶和保护酶活性的影响，以灰飞虱3龄若虫为对象，采用喷雾法比较了S-JS1与5种杀虫剂 (螺虫乙酯、噻虫嗪、吡虫啉、啶虫脒和毒死蜱) 单用，以及菌、药混用对灰飞虱的杀虫活性，测定了灰飞虱取食经S-JS1处理的水稻后，虫体内羧酸酯酶 (CarE)、谷胱甘肽-S-转移酶 (GSTs)、过氧化物酶 (POD) 和超氧化物歧化酶 (SOD) 的活性变化。结果表明:粘质沙雷氏菌S-JS1分别与不同浓度杀虫剂混用，均可提高杀虫剂对灰飞虱的致死率。其中，109 cfu/mL的S-JS1与1.25 mg/L的噻虫嗪混用处理3 d，或与25 mg/L的螺虫乙酯混用处理5 d，灰飞虱的死亡率分别为65.58%和76.27%，均显著高于同浓度杀虫剂单用的处理 (噻虫嗪单用时致死率为44.24%，螺虫乙酯为49.22%)，表现为增效作用 (χ2 > 3.84，实测死亡率 – 预期死亡率 > 0)；其他各混用处理均为相加作用 (χ2 < 3.84)。灰飞虱取食经粘质沙雷氏菌处理的水稻苗后12和24 h，其CarE活性与对照组间无显著性差异，GSTs活性呈先降低后升高趋势，POD和SOD活性均低于对照组。研究表明，粘质沙雷氏菌S-JS1可能降低了灰飞虱对杀虫剂的抵抗力。本研究可为探索昆虫病原细菌与杀虫剂间的联合应用提供参考，为灰飞虱的有效防治提供新思路。

Combined effects of Serratia marcescens S-JS1 with five insecticides against Laodelphax striatellus and the effect of S-JS1 on activities of relative enzymes in L. striatellus

The objective of this study is to evaluate the efficacy of combinations of Serratia marcescens isolate S-JS1 and insecticides against Laodelphax striatellus, and to investigate the effect of S. marcescens on the detoxifying and protective enzymes of L. striatellus. Third-instar nymphs of L. striatellus were used in all experiments. The efficacy of 5 insecticides (spirotetramat, thiamethoxam, imidacloprid, acetamiprid, and chlorpyrifos) alone and mixed with S. marcescens against L. striatellus were compared by spraying method. After L. striatellus feeding on S. marcescens-treated rice seedling, the activity changes of carboxylesterase (CarE), glutathione-S-transferases (GSTs), peroxidase (POD), and superoxide dismutase (SOD) in it were determined. The results showed that combinations of S. marcescens with insecticide of any concentration resulted in higher L. striatellus mortality compared to the effect achieved by insecticide alone. Compared to the mortality effect against L. striatellus using 1.25 mg/L thiamethoxam (44.24%) or 25 mg/L spirotetramat (49.22%), applications of 109 cfu/mL S. marcescens + 1.25 mg/L thiamethoxam for 3 days (65.58%) or 109 cfu/mL S. marcescens + 25 mg/L spirotetramat for 5 days (76.27%) show significantly higher activities. And interactions resulted in a synergistic responses (χ2 < 3.84, observed mortality – expected mortality > 0). Other combination treatments of S-JS1 with insecticide of any concentrations all exhibited additive interactions. 12 and 24 h after L. striatellus feeding on S. marcescens-treated rice seedling, there was no significant difference in CarE activity between the treatment group and the control group. The activity of GSTs increased initially, then decreased. The activities of POD and SOD were always significantly lower than those in the control. Therefore, S. marcescens S-JS1 may weaken the defense activity of L. striatellus against insecticides. This study provides reference for exploring the combined applications of entomopathogenic bacteria and insecticides, and may provide a novel clue for the control of L. striatellus.