Studies On Physiological Mechanism And Para Channel Gene Fragment Cloning And Expression Of Indoxacarb Resistance In Diamondback Moth(Plutella Xylostella)

Plutella xylostella(L.) is one of the most important crucifers vegetables pests in the world.It has developed resistance to more than fifty kinds of chemical insecticides because of large-scale use chemical insecticides and the particularity of the diamondback moth life history.Its prevention and control is becoming the world’s most difficult work,so it can be called the resistance "mode pests".Indoxacarb was a novel insecticide belonging to the oxadiazine class with unique action mechanism, excellent insecti-cidal activity and low toxicity to no target organisms; it was therefore an ideal candidate to substitute organophosphate and pyrethroid insecticides. Meanwhile, indoxacarb would be the study hot topics and people’s attention in the future.In this paper, the toxicological characteristics of indoxacarb against Plutella xylostella had been studied, which including physiological mechanism of resistance and target molecular mechanism of resistance.l.The activities of defending enzymes were analyzed in the susceptible,field population and resistant strains.The results showed there were no significant differences in the activities of SOD, POD and CAT among the three strains.The activities of larvae from all three strains increased significantly with indoxacarb LC50dose.It was also found that the defending enzymes activities of different development stages both the susceptible and resistant strain were related to their larva instars.2.The effects of indoxacarb on the respiratory rates of3-4instar larvae of a susceptible strain (S), a field population, and a resistant strain of Plutella xylostella (L.) were investigated. The results showed that there were no significant differences in respiratory rates of larvae of the same instar among the three strains, and that increased resistance to indoxacarb did not change the fundamental respiratory rate. The respiratory rates of larvae from all three strains increased significantly with increasing indoxacarb dose. It was suggested that there is a degree of correlation between increased respiratory rate and the ability to detoxify indoxacarb in Plutella xylostella (L.) larvae. These results indicate that the energy consumption of treated larvae increases with indoxacarb resistance level.S.cDNA fragments of269bp in length in the IIS5-IIS6region of sodium channel para-orthologous gene in both resistant and susceptible strain were amplified with a pair of specific forward primer and reverse primer by using RT-PCR method. The result showed that there was no sodium channel mutation in the resistant strain compared with the susceptible strain.4.The differences of plutella xylostella para sodium channel gene expression were determined by combing SemiQuantitative RT-PCR with realtime PCR technology.The result showed that the gene expression existed in different developmental stages and different tissues of Plutella xylostella.But the level of the relative expression was different, such as adult epression was the highest and lowest pupae.There was no obvious difference among the larvae of different tissues.