Production Of Insect-resistant Rice Through Bt Genes Transformation

Stemborers and leaffolders are two groups of Lepidopteran pests that cause severe damage to rice in many areas of the world. Minghui 63 is an elite indica restorer line, but it is highly susceptible to lepidopteran insects, which greatly reduce the expected yield of Minghui 63 and its derived hybrid. In this study, a cry1C^* gene encoding Bacillus thuringiensis (Bt) d-endotoxin was synthesized by codon optimization as one step toward gene stacking in our resistance management strategy of transgenic rice. This gene and a cry1Ab gene were transformed into Minghui 63 (Oryza sativa L.) via Agrobacterium.The integration of the transgene was confirmed through PCR analyses. Southern analysis of transgenic plants showed that different transgenic plants had varied transgene copies. Homozygous transgenic plants were produced through seed germination testing. The Bt protein quantification was completed through ELISA. It was shown that T_1C-19, T_1Ab-6 and their derived hybrids were highly resistant to stemborers and leaffolders throughout the growth period and also had good agronomic traits. These results indicate that T_1C-19 and T_1Ab-6can be used for production of insect-resistant hybrid rice, and as a germplasm for gene stacking to produce rice with two toxins.In 2005, the transgenic lines T_1C-19 and T_1Ab-6 were approved for medium-sized test of the safety assessment. For the time being, these transgenic lines and their prelimarily stacked plants were undergoing test for further insect resistance and genetic stability. These lines are expected approved for environment-release test very soon.Main research results are as follows.1. Expression vectors pBar-1C^* (harboring with cry1C^*) and pBar-lAb (harboring with cry1Ab^*) were constructed and were transformed into the embryogenic calli of Minghui 63. Finally, 120 crylC^* and 92 cry1Ab independent transformants were obtained respectively.2. Southern blotting analyses showed that 19 of 120 cry1C^* and 13 of 92 cry1Ab independent transformants had single-copy insertion. Through seed germination test, 11 cry1C^* and 9 cry1Ab homozygous lines were obtained.3. Target transgenic plant families in the T₁ generation were selected based on four criteria: (1) high insect resistance, (2) no obvious phenotypic changes, (3) a single copy of the transgene, and (4) Mendel segregation. From 11 single-copy cry1C^* plants and 9...