Resistance Of Transgenic Bt Rice Against Chilo Suppressalis(lepidoptera: Crambidae) Larvae And Effect On Its Oviposition Choice Behavior

Rice is one of the most important crops, and the stable food for more than half of the world’s population. However, some pests like Chilo suppressalis(Walker) and Tryporyza incertulas(Walker) cause damage to rice tissues, resulting in severe yield losses. The long-term employment of chemical insecticides has resulted in a serious of problems, such as environmental pollution, human health problems, and the development of pest resistance to the insecticides. Genetially engineered(GE) rice expressing Bt insecticidal proteins offers a clean and effective approach for rice pest control. So far, multiple transgenic Bt rice lines have been developed in China, which lay the foundation for rice pest control using Bt rice lines in the future.In this study, three transgenic rice lines, T2A-1, T1C-19, Huahui NO.1(Huahui 1), and the corresponding nontransformed near isoline Minghui 63 were used for the experiments. The seasonal expression of Cry proteins in different tissues of the rice lines and their resistance to C.suppressalis were assessed in comparison to Huahui 1. Additionally, the effects of Bt rice on the females oviposition behavior were tested by laboratory, greenhouse and field experiments. The main results are listed as following:1. The results of ELISA indicated that in general levels of Cry proteins were T2A-1 > Huahui 1 > T1C-19 among rice lines, and leaf > stem > root among tissues. The expression patterns of Cry protein in the rice line plantswere similar: higher level at early stages than at later stages. The bioassay results revealed that the three transgenic rice lines exhibited significantly high resistance against C. suppressalis larvae throughout the rice growing season. According to Cry protein levels in rice tissues, the raw and corrected mortalities of C. suppressalis caused by each Bt rice line were the highest in the seedling and declined through the jointing stage. T1C-19 exhibited more stable and greater resistance to C. suppressalis larvae than T2A-1.2. The orientation of C.suppressalis females to different rice plants in the wind tunnel showed that C.suppressalis female adults could distinguish between MH63 rice plants and Huahui 1 rice plants, showing an a tendency to control rice line MH63.3. The influence of transgenic rice plants on C. suppressalis females oviposition was examined in plastic mesh covered cages in the greenhouse. No signiticant difference was found for oviposition by C. suppressalis females between healthy rice plants of transgenic rice plants Huahui 1 and MH63. The females preferred to oviposite on MH63 rice plants when Huahui 1 and MH63 rice plants fed by 3th instar larvae for 72 h in the greenhouse.4. In the field condition, C.suppressalis females preferred ovipositing on MH63 rice plants compared to the transgenic rice plants Huahui 1.