| The cotton bollworm, Helicoverpa armigera (hubner) is one of the most serious destructive pests in China. These years along with the promotion of transgenic Bt cotton, transgenic cotton field has become the important trapping host. So it is particularly important to further study the host selection and monitor the resistance change on transgenic cotton. In this paper, In order to provide scientific basis for resistant use and comprehensive management of transgenic Bt cotton, we focused on the oviposition and behavioral response of different strains of H. armigera on transgenic Bt cotton. We also determined the content of olfactory related genes of different strains of H. armigera and discussed the resistance changes between field and sensitive strains of generations under laboratory feeding condition continuously. The main results were as follows:1. Using the method of refining adults in field cages, we surveyed the oviposition of sensitive and field strain of H. Armigera adult, as well as growing conditions of field strains. The results showed that the each index of growing in different treatment was more consistent while the number of eggs of field insect on transgenic cottons was higher than conventional cottons. In addition, the difference which was manifested by the number of eggs of indoor sensitive insect on transgenic and conventional cottons was not significant.2. To determine the selectivity of different strains of H. armigera in odor source of three groups under first and third instar using the method of petri dish leaf disc. The first instar in three strains of H. armigera tented to choose un-transgenic cotton mostly. But to third instar, sensitive strain was the only to choose un-transgenic cotton while the trend of the other two strains on Bt cotton and No-Bt cotton was not obvious.3. Applying Y-tube olfactometer to study the selective tropism of different strains of H. armigera in odor source of four groups(Shiyuan321 and SGK321; Simian3 and GK22; Zhongmian23 and Zhongmian41; Zhongmianl6 and Zhongmian30), we found that we found that the field strain collected in 2012, male and female moths after mating of field strain collected in 2013 as well as unmated males, females and the males after mating of sensitive strain tended to choose Bt cotton except that the unmated females of field strain collected in 2013 prefer to No-Bt cotton.4. In seedling and squaring stage, using bioassay method to measure the resistance on transgenic Bt cotton varieties in different strain of H. armigera. All Bt toxin contents of GK22, Zhongmian30 and Zhongmian41 in seedling and squaring stage we measured were above 600.00ng/g. Moreover, according to the resistance of different strain of H.armigera on the same transgenic cotton was highly consistent, we could see that the field strains of H. armigera involved in this study did’t produce resistance.5. Determining the content of olfactory related genes(CSP, OBP and PBP) with different strains of H. armigera adult, we concluded that the expression of CSP5 and CSP6 genes in field strains took different degrees of increase except for cutting of CSP6 genes in unmated females compared with sensitive strain. The expression of OBP2 and OBP6 genes was no significant difference between twelve generations collected in 2012 and sensitive strain while OBP2 gene’s expression acquired from 2012 and 2013 strains reached significant or extremely significant difference compared with the sensitive strain. In addition, the expression of OBP6 gene of field strains was also not significant with sensitive strain except of the field strain in 2012. Apart from this, we also found that the expression of PBP1, PBP2 and PBP3 genes of 2012 and 2013 strains was significantly higher than the sensitive strain while that in twelve generations’ strain was significantly declined.Comprehensive the above results, we concluded that there were some differences in oviposition and behavioral response of different strains of H. armigera as well as the content of olfactory genes(CSP, OBP and PBP). But the field strain of H. armigera was still sensitive rather than resistant on transgenic Bt cotton. |
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