Evaluation Of Pyramiding Bt Cry1Ac And Cry1Ie Corn For Resistance To The Asian Corn Borer And Its Effect On IRM

Asian corn borer(ACB), Ostrinia furnacalis(Guenée), is one of the most important pests of maize in China. There are some shortcomings in the traditional methods of prevention and cure. Transgenic maize which expresses Bt toxin efficiently in the whole development stages provided a new way to control ACB. However, the evolution of the target pest resistant population will threaten the sustainable application of Bt maize. It is a major challenge for preventing pests from developing resistance to Bt toxins produced by transgenic crops for agriculture. Theoretical models suggested that plants contained two dissimilar Bt toxin genes which were the potential to delay resistance more effectively than single-toxin plants used sequentially or in mosaics. To test these predictions, transgenic corn plants carrying cry1 Ac, cry1 Ie or both genes were obtained. At the same time, valuates the tolerance of glyphosate of insectresistant/glyphosate-tolerance bivalent corn and glyphosate-tolerance corn, and measured the quantity of Cry1 Ac and CP4 EPSPS protein expressed in corn tissues, in order to provide the basis for the improvement and application of the maize varieties.Field tests showed that minimal damage was seen for leaf feeding on Bt corn under artificial infestation with ACB at mid-whorl. The leaf feeding rates of Bt corn was lower than 2, with a mean of 5 to 8 in conventional corn The number of larvae surviving evaluated per plant was lower than 0.11 in Bt corn. The number of holes evaluated per plant was lower than 0.59 in Bt corn. The number of tunnel length evaluated per plant was lower than 1.06 in Bt corn. To evaluate the resistance of pyramiding Bt corn to ACB, Laboratory bioassays were carried out by exposing susceptible or different resistant Asian corn borer neonates to fresh Bt corn whorl, immature tassels, fresh silks and husk. Mortality indicated that pyramiding Bt corn have more effective insecticidal efficacy to both susceptible and resistant Asian corn borer. Laboratory bioassays and protein quantification indicated that pyramiding Bt corn have significant control efficiency to resistant ACB strains. The morality of ACB-Ie R was low when feeding on cry1 Ie transgenic Bt corn. The morality of ACB-Ac R was low when feeding on cry1 Ac transgenic Bt corn. The morality of ACB-FR was low when feeding on cry1 Ac transgenic Bt corn. It is well established that synergism occurs to varying degrees between the Cry1 Ac and Cry1 Ie. Moreover, the SF values obtained in all the combinations tested against the ACB-Bt R except when the ratio was 5:1 in ACB-Ac R, Cry1 Ac and CP4 EPSPS protein expression are measured by Elisa. The CC-2 and CC-2×BT799 had good tolerance to glyphosates, Growth was normal after spraying glyphosate with medium and double does at the whorl stag. Elisa detection showed that CP4 EPSPS protein expression in the tassel slightly higher than leaf. CP4 EPSPS protein expression in CC-2×BT799 is a little higher than CC-2. Cry1 Ac protein expression in BT799 and CC-2×BT799 are nearly the same in the tassel. However, Cry1 Ac protein expression in leaf of BT799 is about 2 times of CC-2×BT799. Insect-resistant/glyphosate-tolerance corn can effectively resist glyphosate spraying. Cry1 Ac protein expression is different in different varieties of different tissues.The results showed that four kinds of transgenic insect-resistant maize all have better results with controls. For different tissues, it is the most poor in filaments to insect resistance. And virulence protein bioassayshowed that the effects on various resistant strains of different proportions were incraesed. In the sensitive strains, the best ratio of Cry1 Ac toxin and Cry1 Ie is 5: 1, which means better results In combination with two measures. For Glyphosate, the multiple Transgenes individual CC-2 × BT799 and Single individuals resistant to glyphosate CC-2 have good resistance to glyphosate. But there is no significant impact on the growth and plant height for spraying glyphosate the normal dose and twice at the whorl stage of the corn.