The Insecticidal Effect And Bio-safety Of Six Types Of Bt Protein To Three Kinds Cotton Insects

China began to plant Bt cotton for more than fifteen years since1997. The area increased year byyear.However, it easily lead to cotton bollworm increased resistance to Bt protein beause of long-termcultivation. In order to delay the target pest resistance to Bt protein, it was necessary to cultivatetransgenic double or multivalent Bt gene. Therefore, in order to clarity the insecticidal effect andbio-safety of new Bt protein to three kinds cotton insects and natural enemy. The paper hadsystematically studied the effects of six Bt proteins on the insecticidal effect, growth and developmentagainst three main insects in cotton with the help of ecology, physiology and toxicology. In addition, weresearch the effects of Cry1Ah insecticidal protein on the growth and development, body enzymeactivity of Propylea japonoca as well as biotransfer of Cry1Ac protein in the artificial diet-Spodopteraexigua-Propylea japonoca food chain. Therefore, this will help to improve the evaluation of ecologicalsafety of new Bt gene crops. The main conclusions of the study were as follows:1We studied the effect of LC50of six different Bt protein to cotton bollworm larvae, Helicoverpaarmigera by using the method of bioassay. LC50were Cry1AbCry1Ab:0.065ug/g, Cry1Ac:0.074ug/g,Cry2Ab:0.133ug/g,Cry2Aa:11.670ug/g,Cry1Ah:13.010ug/g and Cry1Ca＞20ug/g.The results indicatedCry1Ab and Cry1Ac were the most effective Cry toxins to cotton bollworm larvae; Cry2Ab secondly.However, Cry1Ah and Cry2Aa were very little effective against the larvae and Cry1Ca was not toxic.2The effect of different Bt protein on the mortality, growth and development of cotton bollwormlow-instar larvae was discussed. The results demonstrated Cry1Ab and Cry1Ac display the strongesteffect against cotton bollworm larvae among all Bt protein. Abbott-corrected mortalities and weightinhibition rate were about90%. Second-instar larvae treated by Cry1Ac or Cry1Ab, it had slow weight;the mortality after11d was nearly to40%; pupation and emergence rate was almost zero. Cry2Absecondly. Abbott-corrected mortalities and weight inhibition rate were60%and90%. Moreover,first-instar larvae displayed no difference on corrected mortality (25%) and weight inhibition rate (60%)between Cry1Ah and Cry2Aa treatment. However, second-instar larvae showed significant differencebetween these two proteins. Cotton bollworm second-instar larvae fed on diet containing1.0ug/gCry1Ah protein, body weight and larvae development parameters had no significant differencescompared with Cry2Ab.Cry1Ca has almost no effect on the survival rate, growth and developmentcompared with the control.3We discussed the influences of different concentration of Cry2Ab protein on survival rate andweight inhibition rate against the low-instar larvae of Spodoptera exigua and Spodoptera litura. Theresults showed that at high concentration (10.0ug/g and20.0ug/g),7d survival rate of Spodopteraexigua neonate larvae were51.39%,44.44%, significantly lower than the control (80.39).7d survivalrate of Spodoptera exigua first-instar larvae were35.99%treated by20.0ug/g, significantly lower thanthe control (65.30%).Compared with the control, at different concentration treatment, beet armywormlarval body weights were obviously inhibited. The stronger body weights inhibit the higher Cry2Abconcentration. However，survival rate of Spodoptera litura larvae showed no significant differences compared with the control. Furthermore, it had little influence on the larvae weight. And as the Cry2Abconcentration increasing, larvae body weight inhibited strong.4A tritrophic bioassay was conduced to evaluate the potential impact of Cry1Ah protein on growth,development and enzyme activity of Propylea japonica (Thunberg) using cotton bollworm as prey. Wefound Propylea japonica larvae survival rate, larval weight, development time and pupation rate wereno significant differences compared with the control when they were fed with cotton bollworm larvaereared on1.0ug/g,10.0ug/g or control artificial diet. Some enzymes activity had changed; however,these changes did not affect the growth and development of these larvae. Propylea japonica fed withaphid, Acyrthosiphon pisum survival rate, larvae weight and pupation rate significantly higher than fedwith cotton bollworm; but larvae development time the former significantly shorter than the latter. These data showed different diets have a far larger effect on Propylea japonica than Cry1Ah protein.5We discussed biotransfer and bioaccumulation of Cry1Ac protein in artificial diet, Spodopteraexigua and Propylea japonica food chain by means of conventional bioassay and enzyme-linkedimmunosorbent assays (ELISA). when beet armyworm fed with artificial diets containing1.0ug/gCry1Ac, this toxin was detectable in larval bodies; in addition, as the feeding time increased, the contentof Cry1Ac remaining in beet armyworm larvae body showed the tendency of first increase and thendecrease. But we only detected remaining Cry1Ac toxin in Propylea japonica larvae body when theyfed with Spodoptera exigua larvae treated with Cry1Ac for12h. Because of lower content and persistingfor an extremely short time in its body, remaining Cry1Ac toxin did not have an effect on the growthand development of Propylea japonica larvae.