有机磷/拟除虫菊酯混剂筛选棉铃虫品系的交互抗性和生化机理

 用辛硫磷/氟氯氰菊酯(25：1, 有效成分)混剂对棉铃虫田间种群(HN)进行33代筛选获得抗性品系(HN-R)。筛选获得的HN R抗性品系对辛硫磷和氟氯氰菊酯的抗性分别达17.4倍和144.7倍。HN-R品系对两种拟除虫菊酯产生了高水平交互抗性(对氯氰菊酯和氰戊菊酯分别为86.2和23.4倍)，对久效磷产生了中等水平交互抗性(5.2倍)，对甲基对硫磷(1.6倍)、丙溴磷(1.8倍)和灭多威(2.4倍)产生了低水平交互抗性。酯酶抑制剂DEF能有效抑制HN-R品系对辛硫磷的抗性(增效比为15.3倍)，而多功能氧化酶抑制剂PBO则对辛硫磷没有任何增效作用；PBO则使HN-R品系对3种拟除虫菊酯的抗性显著降低(对氟氯氰菊酯、溴氰菊酯和氰戊菊酯的增效比分别为21.9、19.1和21.4倍)。DEF和PBO都能使HN-R对久效磷的抗性下降一半(增效比分别为2.2和2.5倍)。HN-R抗性品系多功能氧化酶活性(以pNA为底物)和酯酶活性(以a-NA为底物)分别为HN品系的6.5倍和1.6倍。因此，在HN-R抗性品系中至少存在2种代谢抗性机理，即增强的酯酶解毒代谢(对辛硫磷、久效磷)和多功能氧化酶介导的氧化解毒代谢(对3种拟除虫菊酯、久效磷)。本研究表明，在田间使用有机磷/拟除虫菊酯混剂可能同时选择出多种代谢抗性机理，从而导致广谱的交互抗性。

Cross Resistance Patterns and Biochemical Mechanisms in a Chinese Helicoverpa armigera Strain Selected with an Organophosphate/Pyrethroid Mixture

Selection of a field strain of Helicoverpa armigera (HN) was undertaken by treatment with a mixture of an organophosphate (phoxim) + a pyrethroid (cyhalothrin) (25:1, a.i.) for 33 generations. The resistance to phoxim of the selected strain (HN-R) increased to 17.4-fold and the resistance to cyhalothrin increased to 144.7-fold. High level cross-resistance to two pyrethroids was detected (86.2-fold to deltamethrin and 23.4-fold to fenvalerate) in the HN-R strain. In addition, the HN-R strain also possessed a moderate level of cross-resistance to monocrotophos (5.2-fold), a low level cross-resistance to methyl parathion(1.6-fold), profenofos (1.8-fold), and methomyl (2.4-fold). The esterase inhibitor S,S,S-tributylphosphorotrithioate (DEF) was very effective in reducing phoxim resistance of the HN-R strain (with a synergism ratio of 15.3-fold) but the mixed function oxidase (MFO) inhibitory synergist piperonyl butoxide (PBO) had no synergism to it at all. In contrast, PBO dramatically removed most of resistance to three pyrethroids with synergism ratios of 21.9-fold to cyhalothrin, 19.1-fold to deltamethrin, and 21.4-fold to fenvalerate, but DEF had no synergism to them. Both DEF and PBO can remove about half of the resistance to monocrotophos (with synergism ratio of 2.2- and 2.5-fold, respectively). Compared to the reference HN strain, the MFO activity of the resistant HN-R strain to p-nitroanisole (pNA) was 6.5-fold and total esterase activity to 1-naphthyl acetate (a-NA) was 1.6-fold. At least two metabolic resistance mechanisms are involved in this resistant HN-R strain: esteratic detoxification (to phoxim and monocrotophos) and oxidative metabolism by mixed function oxidases (to pyrethroids and monocrotophos). The results suggest the use of pyrethroid/organophosphate mixtures in the field is likely to lead the simultaneous selection of multiple metabolic mechanisms of resistance, and thus a broad cross-resistance spectrum.