寄主抗药性对菜蛾绒茧蜂抗药性发展的影响

室内筛选小菜蛾中抗品系（SRP）、高抗品系（RP）、以敏感小菜蛾幼虫（SP）为寄主的菜蛾绒茧蜂SRC品系和以SRP幼虫为寄主的菜蛾绒茧蜂RSC品系对氰戊菊酯的抗性。分别筛选了13、14、14和13代。小菜蛾SRP和RP品系分别获得了68.9和605.8倍的抗性，菜蛾绒茧蜂SRC和RSC品系分别获得了4.3和11.0倍的抗性。上述结果表明通过施药于体内有寄生蜂的小菜蛾幼虫筛选寄生蜂抗性，可以获得具有抗性的寄生蜂。以SRP为寄主的RSC品系的抗性水平高于以SP为寄主的SRC品系的抗性水平，表明和抗性较高的寄主同步筛选，寄生蜂的抗性发展更快。小菜蛾SP、SRP和RP三个品系幼虫的多功能氧化酶（MFO）活性比为1∶1.15∶1.50；菜蛾绒茧蜂SC、SRC和RSC三个品系幼虫的MFO活性比为1∶1.10∶1.49，成蜂的MFO活性比为1∶1.18∶1.54;而每种昆虫不同品系的羧酸酯酶（CarE）、总酯酶（Es）活性水平与其抗性水平变化不一致，表明抗性与MFO活性升高有关，而与CarE和Es的活性无关。

The effect of host insecticide resistance on the development of resistance to fenvaler-ate in Cotesia plutellae ( Hymenoptera : Braconidae)

Individuals were selected for increased resistance to fenvalerate in the SRP (moderate resistance) strain and RP (high resistance) strain of Plutella xylostella, and in SRC and RSC strains of the parasitoid Cotesia plutellae. The SRC strain of C. plutellae was reared on a susceptible strain of P. xylostella larvae (SP), and the RSC strain was reared on SRP larvae. Selection for SRP, RP, SRC and RSC was carried out for 13, 14, 14 and 13 generations respectively. The SRP and RP strains of P. xylostella acquired 68.9 and 605.8 fold resistance, while the SRC and RSC strains of C. plutellae acquired 4.3- and 11.0-fold resistance, respectively. These results show that fenvalerate resistance by C. plutellae can be selected by applying the insecticide to host larvae harbouring the immature parasitoids. Moreover, the resistance level of the RSC strain was higher than that of the SRC strain, demonstrating that selection with more resistant hosts can accelerate the development of resistance in the parasitoid. Ratios of MFO activity in the SP, SRP and RP strains of P. xylostella were 1∶1.15∶1.50; ratios of MFO activity in larvae of the SC, SRC and RSC strains of C. plutellae were 1∶1.10∶1.49, and in the adults of the three strains of the parasitoid were 1∶1.18∶1.54, respectively. However, changes in the specific activities of CarE and Es in the different strains of each insect species did not show a similar trend to the resistance levels. These results indicate that fenvalerate resistance in C. plutellae is positively related to MFO activity, but unrelated to CarE and Es activity.