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Study On The Toxicity Difference And Mechanisms Of Two Bt Proteins In Agrotis Ypsilon

Posted on:2009-10-05Degree:MasterType:Thesis
Country:ChinaCandidate:Q LuFull Text:PDF
GTID:2143360245972645Subject:Agricultural Entomology and Pest Control
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Bacillus thuringiensis(Bt) is the most important insecticide in the field of biological control. Agrotis ypsilon is also an important agricultural insect pest.With the growing rate of resistance to Bt, function mechanism of Bt to insect and resistance mechanism of insect to Bt are studied widely. Function mechanism of Bt to Agrotis ypsilon is studied in this thesis.The results are as follows:1 Bt Cry2Ab toxin has high toxicity to Agrotis ypsilon, but Cry1Ac has low toxicity to Agrotis ypsilon.2 Growth and development effects of Bt on Agrotis ypsilon changed obviously.After the new incubated larvae fed on Bt proteins in different dose, the mortality, larval weight, pupation, pupal weight and eclosion declined, and the larval and pupal duration were prolonged. After feeding on the Bt proteins .Cry2Ab id the most toxic to Agrotis ypsilon, indicating the Cry2Ab is the most effective.3 After the larval fed in Bt protein, the activities of midgut protease changed.The activities of midgut total protease and chymotrypsin-like proteinase of the larval feeding on Cry2Ab increased; The activities of midgut aminopeptidase of the larval feeding on Cry2Ab concentration 12μg/g increased. The activities of midgut protease of the larval feeding on Cry1Ac did not change obviously. The activity of glutathione s-transferase of Agrotis ypsilon feeding on Cry2Ab increased and is higher than Helicoverpa armigera feeding on Cry2Ab.4 The mid-gut juice enzyme activity of Agrotis ypsilon is higher than Helicoverpa armigera. 130kD Bt pro-toxin is decomposed by mid-gut juice in 37℃, 60℃toxin can be got by Helicoverpa armigera and Agrotis ypsilon mid-gut juice, but, other less than 60kD proteins also can be got by Agrotis ypsilon mid-gut juice.5 The length cDNA cadherin-like receptor in Agrotis ypsilon were cloned with PCR methods. The deduced gene sequence of cDNA from Agrotis ypsilon was 1136bp and showed 64% with B.mori, 64% with O.nubilalis, 63% with L.dispar, 65% with H.zea, 67% with H.Virescens, 64% with M.Sexta.According to design of degenerate primers, the cadherin-like receptor in Agrotis ypsilon was hightly similar to other lepidopteran cadherin-like receptor. The deduced amino acid of cDNA from Agrotis ypsilon was 379 and showed 63% with 44B.mori, 62% with O.nubilalis, 64% with L.dispar, 65% with H.zea, 63% with H.Virescens, 63% with M.Sexta.
Keywords/Search Tags:Agrotis ypsilon, Bacillus thuringiensis, activity of Midgut protease, Cadherin-like
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