Effects Of Nitrogen Fertilization On The Insect Resistance And Grain Yield Of Bt Rice

Rice is the most important food crop and is the stable food source for more than a third of the world’s population. However, it is estimated that about20%-30%of the rice yield is lost because of the pests. At present, pest control is mainly through the application of chemical pesticide. However, unreasonable use of pesticide has brought a series impact on product safety and environment.The toxic Bt crystal proteins derived from the bacteria can specially kill the pests and protect the rice from yield loss.And planting the transgenetic Bt rice can reduce the consumption of pesticide, and can reduce the cost. The genes for toxic Bt crystal proteins have been transfer into more than50plant species, such as cotton, rice, corn, and so on. Cry1is a set of highly homologous genes, whose products can specially kill Lepidoptera pests. Cry protein is encoded by the genes of CryIAb and CrylAc. They show high toxicity to Chilo suppressalises, Paddy stem borers and Leaf folders.In the present study, five transgenic Bt rice cultivars ZY3(cryIAb/Ac*), CL(cryIAb/Ac*),GLY19(cryIAb/Ac*), HXY317(cryIAb/Ac*), HY675(cryIAb/Ac*), and three non-transgenic rice cultivars, YLY6, ⅡY838and JY207, were used.In2011, three different nitrogen application rates (90,135,180kg N/ha) were applied. In2012, four different nitrogen application rates (0,90,135,180kg N/ha) were applied. The major objectives were:(1) to study the effects of different nitrogen application rates on yield and yield components of transgenic Bt rice and non-transgenic rice cultivars;(2) to study the differences in pest resistance among transgenic Bt rice and non-transgenic rice cultivars. The results obtained were listed as following:1. With pesticide, there was no significant difference in rice yield between transgenic Bt and non-transgenic rice cultivars. Without pesticide, the yields of transgenic Bt rice cultivars were significantly higher than those of non-transgenic rice cultivars. Compared with pesticide treatment, the yield of YLY6and IIY838without pesticide were reduce by36.8%and31.9%, the average loss was34.4%. While the yield of transgenic rice cultivars were reduce by19.9%,14.4%,9.8%and8.1%in GLY19, HXY371, ZY3and CL, respectively, the average loss was13.75%.2. Without pesticide, the percentages of white leaves and dead hearts of transgenic Bt rice cultivars were significantly lower than that of non-transgenic rice cultivars. In2011, the percentages of white leaves in GLY19and the other Bt rice line at different growth stage were less than10%, while they were higher than20%, even as much as50%in YLY6. The percentage of dead heart in YLY6was significantly higher than those in transgenic rice cultivars. In2012, the percentage of white leaves in YLY6was less than10%, but was significantly higher than those in transgenic rice cultivars.3. The concentration of toxic protein increased with nitrogen application rate. There was a positive correlation between SPAD value and Bt protein content. The correlation coefficients between SPAD value and Bt protein content in middle tillering, panicle initiation, heading stage and milk period.