Characteristics Of Nitrogen Absorption And Utilization Of Two-line Bt (Cry1Ab/Ac) Transgenic Hybrid Rice

Bt transgenic crops have been reported to be effective in controlling lepidopteran pests, and some Bt transgenic lines are further used to develop transgenic hybrid rice. In recent years, two-line Bt transgenic hybrid rice breeding has gained success. However, it is obscure whether the insertion of external Bt gene affects growth, nitrogen uptake and nitrogen use efficiency of the two-line Bt transgenic hybrid rice, drawing the attention of the academia. Therefore, field experiment was conducted at Zhangbang village, Wuxue city, Hubei province, China in2011and2012. Eight two-line Bt (CrylAb/Ac) transgenic hybrid rice (Bt-THR) were used, which were the Pedigrees of Huahui1, the two-line hybrid rice (THR) control was Yangliangyou6(YLY6). The objectives of the experiment were to research (1) the growth characteristics of Bt-THR;(2) the effect of fertilizer-N rate on Bt protein concentration in flag leaves of Bt-THR;(3) the grain yield and NUE characteristics of Bt-THR and THR. The main results are as follows:1. There was no significant difference in main agronomic traits between Bt-THR and the control YLY6, but some of Bt-THR demonstrated a comparable maximum grain yield with the super hybrid rice YLY6.2. No significant differences were observed in the grain yield between GLY19, ZY3and YLY6with N application in both2011and2012. CY4198, relative to non-Bt control YLY6, had lower average grain yield in2011. The grain yield of CY4198was significantly higher than YLY6at90kg N hm-2, but no difference in average grain yield were observed in2012.3. The response of grain yield to N treatments varied among different Bt-THR varieties and the control. In2011, there was no significant difference in grain yield for all varieties at different fertilizer-N rate, except for ZY3, that showed maximum grain yield at180kg N hm-2. With the increase of N application, grain yield decreased for GLY19and CY4198due to lodging. In2012, CY4198showed maximum grain yield at90kg N hm"2, but other Bt-THR varieties similar to YLY6that showed maximum grain yield at135kg N hm-2.4. No significant differences were observed in the N accumulation and N concentration between Bt-THR and YLY6. YLY6and CY4198had lower agronomic nitrogen use efficiency than GLY19and ZY3, due to higher grain yield at zero N fertilizer application in2012.5. Bt protein concentration in flag leaves of Bt-THR increased with increased fertilizer-N rate, while the Bt protein concentration in flag leaves with fertilizer-N rate did not show the consistency rule at heading and flowering stage, but the Bt protein concentration was higher than the control target pests need to reach threshold. During the whole growth period Bt protein expression reached to the highest levels at booting stage.The insertion of Bt gene does not significantly change the N uptake and use efficiency of rice. Therefore, the knowledge with developed technologies of fertilizer-N management for increase in grain yield and NUE on super hybrid rice can provide a reference to Bt-THR.