Improvement Of The Resistance To Insect, Disease And Herbicide Of Rice Cultivars By Transgenic Approach

In order to improve the resistance to disease, insect and herbicide of rice cultivars by genetic engineering, four Japonica rice cultivars, Guanglingxiangjing, Wuxiangjing 9, 4901, and Wuxiang 99-15, and two Indica rice cultivars, Zhenshan 97 and Xieqingzao, were used for transformation with four target genes mediated by Agrobacteriam. The four target genes are Bacillus thuringiensis (Bt) cry I A(c) toxin gene, the ferredoxin-like protein (Ap1)gene encoding an amphipathic protein from sweet pepper, the Galanthus nivalis agglutinin (GNA, snowdrop lectin) gene, and Bar gene from Streptomyces hygroscopicus, which had been proven to resist the stem borer, bacterial blight disease, sap-sucking insect pests, and Basta herbicide respectively, after expression in transgenic rice plants.By using the twin T-DNAs co-transformation system, many co-tranformed rice plants were generated in each target rice variety. Subsequently, in the self-pollined progeny of co-transformants, several selectable marker-free (SMF) transgenic rice lines were screened, and the resistance to diseases and insects of transgenic rice plants were carefully analyzed.The results were showed as followings:1. Two twin-T-DNA co-transformation systems, i.e. two vectors/two strains and super binary vector (two separate T-DNA regions at one binary vector), were used and their co-transformation efficiency in rice were compared. A large number of co-transformants were produced, and the results from molecular analysis showed that, the co-transformation frequency of the target gene and marker gene was higher with thesuper binary vector system than that with the two vectors/two strains system. But, the frequency of segregation of the target gene and marker gene in the offspring of co-transgenic plants was lower in the super binary vector system than that of the two vectors/two strains system. Finally, the frequency of SMF transgenic rice plants obtained was higher with the super binary vector system when compared with the two vectors/two strains system. Several SMF transgenic rice lines were subsequently selected for further resistance assay and field test.2. It was identified that the selected transgenic rice lines showed enhanced resistance to insect(s), desease(s), and/or herbicide during either in vito or in vivo bioassay. The neonate larvel mortality rates of striped stem borer reached 100% in an insect bioassay with the Bt transgenic rice plants. The transgenic rice lines containing homozygous GNA gene showed significantly improved resistanct to the Brown planthopper (Nilaparvata lugens,BPH), e.g. decreased Brown planthopper survial and overall fecundity, and declined BPH feeding. In the Ap1 transgenic rice lines, the desease resistance were also increased after infection by both Xanthomonas oryzae pv. Oryzae and Rhizoctonia solani. The transgenic rice carring Bar gene was identified to high tolarance to the herbicide Basta containing PPT active elements.3. In the small-scale field trials, no significant difference was found in main agronomic traits between the most of selected homozygous transgenic rice lines and their non-transformed wild type, only smaller transgenic rice had variation at some extent.4. Both co-transformation approaches and conventional crossing were used for combined the four target genes into one single variety.