Cry1Ie Confers Resistance to Corn Earworm in Maize

To delay the development of Bt-resistant insects in the field, scientists co-express more than one Bt protein with different modes of action in GM crops. In a study conducted by Yuwen Zhang from China Agricultural University and colleagues, genetically engineered lines of maize over-expressing either Cry1Ie or Cry1Ac genes were developed. Expression of the Bt genes was confirmed through Southern blot analysis. Results of the bioassays showed that plants over-expressing Cry1Ie were highly lethal against corn earworm (Heliothis armigera) with mortality levels reaching 50% after 6 days of exposure. However, the mortality level caused by these plants was lower than that caused by Cry1Ac-expressing plants (80%) and MON810 plants expressing Cry1Ab (100%), which both exhibited low toxicity toward the Cry1Ac-resistant corn earworm. On the other hand, field tests showed that three Cry1Ie-expressing lines had higher mortality against Cry1Ac-resistant corn earworm, as well as to Asian corn borer (Ostrinia furnacalis).

Based on the findings of the study, the mode of action of Cry1Ie is different from those of Cry1Ab and Cry1Ac proteins, and thus may be used to delay the development of pest resistance to Bt in the field.

Read more about the results of the study at http://link.springer.com/article/10.1007/s11240-013-0348-5.