| Summary: | 碩士 === 國立中興大學 === 昆蟲學系所 === 102 === Diamondback moth (Plutella xylostella L.), which causes enormous damage on cruciferous vegetables, can develop resistance very rapidly to insecticides. To effectively manage insecticides resistance, it is necessary to understand the inheritance of insecticide resistance and evaluate the speed of resistant development in diamondback moth. In this study, we used mevinphos an example to investigate the inheritance of insecticide resistance in P. xylostella. Based on our previous studies that acetylcholinesterase (AChE) amino acid substitution associated with resistance to mevinphos, two pure lines, a wild-type SHggt strain and resistant SHMTCN strain carrying A298S, G324A and F386V amino acid substitutions, were established and performed reciprocal cross experiments, bioassays, and mutation frequency analysis. The results showed that the LC50 of parental, SHggt and SHMTCN, and two reciprocal cross progeny, F1and F1’, were 14.9, 775.6, 334.1 and 363.3 μg / ml. The degree of dominance of F1 and F1'' were 0.57 and 0.62. A plateau was found on the log dose –Probit lines of backcrossing and self-cross progeny. These results indicate that the inheritance of mevinphos-resistance in P. xylostella is an incomplete dominant and autosomal trait governed by polygene. In addition, the frequency of AChE gene (ace1) mutation in P. xylostella was found highly correlated with the LC50, the R2 is 0.97. The relaxation of SHMTCN show the resistant ratio 52.01-fold at first generation and decline to 5.48-fold at eleventh generation prove the unstable mevinphos-resistane in P. xylostella. The results show faster development of resistance than recessive inheritance. Therefore, the future of resistant management strategy is to use high doses mevinphos to kill all heterozygous, and to continue monitoring of resistance trends, to rotate insecticides with different mode of action, in order to avoid or delay the resistance in diamondback moth.
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