| Corn is the number one food crop in the world and the third largest food crop in China,becoming an indispensable staple in the daily lives of our people and in the feed processing industry.With an increasing population,rising living standards and a gradual reduction in arable land,the development of genetically modified corn(GMC)has emerged and their commercialisation is imminent.The development of GMC and the assessment of its environmental safety have therefore become an important part of the work of many scientists.In this thesis,four different corn variants,namely,"Double Resistance 12-5"(containing CrylAb+Cry2Aj+epsps)and its control variant "Hongshuo 899","C0030.3.5"(containing CrylAb+epsps)and its control variant "C0010.1.1"(containing epsps+pat)provided by the Agricultural GMO Safety Office of the Ministry of Agriculture and Rural Affairs were used as research material.On the basis of systematic detection of relevant proteins in corn tissues at different stages of reproduction and in different organs and utilizing parameters such as population intrinsic rate of increase and developmental rate,the resistance of these corn variants to corn borer was discussed in depth with the Ostrinia furnacalis as a resistance mediator.The study further investigated the transferring process of related proteins in corn,corn borer and harlequin ladybird and finally the effect of the predatory function of Harmonia axyridis which preys corn borer feeding on GMC.The results of the study are as follows:1.The Bt toxin content in leaves,stalks,stamens,pistils and seeds of both GMC and the controls was systematically measured by ELISA.The result indicates that the Bt toxin content in each tissue and organ decreases over the course of the corn reproductive period and then increases slightly at the grain filling stage.The Bt toxin content in seeds,leaves,stalks,pistils and stamens was 489.49ng/g,487.00ng/g,338.77ng/g,327.50ng/g,154.85ng/g;545.25ng/g,432.66ng/g,329.53ng/g,303.53ng/g,222.45ng/g in Double Resistance 12-5 and C0030.3.5,respectively.2.The experimental results of the phenotype study of populations of two high resistance O.furnacalis feeding on the transgenic corns,Double Resistance 12-5 and C0030.3.5 showed significant differences in the survival rate,developmental process and nymphal weight of the insect compared to the control parent.The study found that the two groups of genetically modified materials are more resistant to the corn borer larvae.The corn borer larvae feeding on genetically modified corn material not only showed high death rate,but also failed to enter the subsequent instar(state)Take the corn borer fed with Double Resistance 12-5 and C0030.3.5 as an example:if you start feeding borer with the first instar larva,the survival rate of the 2nd instar larva of the corn borer fed on two genetically modified corn varieties is only 2.33-8.00%and cannot enter the next instar;the second instar larva of the corn borer fed with two genetically modified corn varieties have a survival rate of 6.67-10.67%and cannot enter the next instar.The survival rate of the second instar larva of the corn borer of a genetically modified corn variants is only 13.33-14.00%when starting feeding with the third instar,and the larva cannot enter the next instar,too.From the point of view of the biological parameters of the corn borer:the O.furnacalis larva that feed on the two kinds of genetically modified corn,Double Resistance 12-5 and C0030.3.5 cannot survive to pupation.The processed part from the 5th instar larva can pupation and emergence,but have significantly lower rate than the two control varieties.3.With the aid of the three-level nutritional relationship of genetically modified corn,target insect corn borer and Harmonia axyridis which is the predatory natural enemy of target insect,the content of CrylAb insecticidal protein in H.axyridis after feeding on the poisonous corn borer was detected by ELISA.The results showed that the toxic protein could be detected in the body of H.axyridis within 24 hours after ingesting the toxic corn borer larva,and the highest concentration in the body reached 0.091ng/g.The predation function of H.axyridis after being poisoned was measured,and the results indicated that there was no difference of the functional response of H.axyridis to the 3rd instar larvae of the corn borer under various treatment conditions The H.axyridis showed similar predation function no matter whether they prey poisonous corn borer,and the functional responses all belong to Holling Ⅱ.It shows that although CrylAb insecticidal protein can be delivered to H.axyridis through the three-level nutritional food chain,it has no adverse effect on the predation function of H.axyridis. |
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