褐飞虱抗甲胺磷品系的交互抗性和抗性生化机制

用甲胺磷筛选的褐飞虱Nilaparvata lugens品系（R），对甲胺磷的抗性达到43.74倍，对马拉硫磷、二嗪磷、异丙威、仲丁威及醚菊酯都表现出一定的交互抗性，而对氰戊菊酯和吡虫啉的交互抗性不显著。为了研究褐飞虱对甲胺磷抗性和对其它药剂交互抗性产生的机制，进行了活体增效试验和离体生化实验。用2 μg/头的增效剂预处理试虫的活体增效实验结果显示，在甲胺磷筛选品系（R）中， TPP(triphenyl phosphate, 磷酸三苯酯)对甲胺磷的增效倍数达到4.54，TPP对马拉硫磷、二嗪磷、仲丁威、异丙威都表现出一定的增效作用，增效比分别为2.76、2.07、2.17和1.64；PBO(piperonyl butoxide,胡椒基丁醚)对甲胺磷、马拉硫磷和醚菊酯有一定的增效作用；DEM(diethyl meteate, 顺丁烯二酸二乙酯)的增效作用不明显。研究离体情况下增效剂对三种解毒酶活性的影响发现，TPP对R品系酯酶活力抑制作用很强（抑制率69.04%），PBO对多功能氧化酶（MFO）具有一定的抑制作用（抑制率29.30%），而TPP和PBO在F品系和S品系中对酯酶和MFO的抑制作用都较小；DEM在三个品系中对谷胱甘肽-S-转移酶的抑制作用都很小。由此可见，酯酶在褐飞虱对甲胺磷的抗性中起最主要作用，在马拉硫磷、二嗪磷、异丙威和仲丁威的交互抗性中起很重要作用；MFO可能在甲胺磷抗性和醚菊酯、马拉硫磷的交互抗性中起一定作用。

Cross resistance of methamidophos resistant strain of brown planthopper and the biochemical mechanism responsible

The R strain selected for methamidophos resistance displayed 43 74 fold resistance to methamidophos and also had cross resistance to malathion, diazinon, isoprocarb, fenobucarb and ethofenprox, but no cross resistance to fenvalerate and imidacloprid. To find out the biochemical mechanism of resistance to methamidophos and cross resistance to other insecticides, we performed synergistic bioassay and biochemical assay. In R strain, the synergistic bioassay showed that TPP (triphenyl phosphate) significantly synergized methamidophos (SR: 4 52) and moderately synergized malathion (SR: 2 76), diazinon (SR: 2 07), fenobucarb (SR: 2 17) and isoprocarb (SR: 1 64). PBO (piperonyl butoxide) partially synergized methamidophos (SR:2 24),malathion (SR: 1 86) and ethofenprox (SR: 1 73). Biochemical assay showed that esterase activity in the R strain was 7 93 times that in S strain,in which the changed activity for MFO was 1 98 and for GST only 1 44 TPP could significantly inhibit esterase activity (PI:69 04%) in the R strain, with MFO's PI 29 30% by PBO. The results indicated that esterase played important role in the biochemical mechanism of methamidophos resistance and, to a lesser extent, cross resistance to malathion, diazinon, fenobucarb and isoprocarb. MFO might play some role in resistance to methamidophos and cross resistance to malathion and ethofenprox.