| Due to the advantage in yield and environment protection, Bt transgenic crops have been well studied since1990s. However, the incorporation of Bt genes into the genome of crops resulted into changes in morphological and physiological traits, for examples, plant height, tillering, N metabolism, K potassium and photosynthesis physiology, and etc. There were few field study about the agronomic performance of Bt transgenic rice before this research, although it was found that Bt transgenic rice lead to reduced grain filling percentage. In our study, MH63(1C*), MH63(2A*), MH63, and SY63(1C*), SY63(2A*),SY63were used in the field experiments from2009to2011. We studied the yield differences between Bt rice and non-Bt rice under insect free condition, and compared their response to different planting dates, N fertilizer treatments and K fertilizer treatments. Under natural insect condition, we studied the occurrence of leaffolders, and the yield advantage of Bt rice over non-Bt control at different N treatments. Our main results are as following:(1) Grain yield of MH63(1C*) was significantly lower than that of MH63(2A*) and MH63, and there was no significant difference in grain yield between MH63(2A*) and MH63. The lower grain yield of MH63(1C*) was due to significantly lower grain filling percentage. No significant difference was found in grain yield among the three hybrid varieties (lines). From the growth analysis, there were no significant differences in leaf area index, biomass accumulation and instantaneous photosynthesis between MH63(1C*), MH63(2A*) and MH63. However, MH63(1C*) had significantly lower NSC (non-structural carbohydrates) translocation from the stem to grain during grain filling stage. This was possibly due to the lower content of ZT, IAA and GA3in the spikelets of MH63(1C*).(2) There were three sowing dates in2009, namely May15,25and June4. Grain yield increased as sowing date delayed. Grain yield were significantly lower when sown in May15than the other two, because it had significantly lower spikelets m2, spikelets per panicle, grain filling percentage. The lower spikelets m"2, grain filling and grain yield were possibly due to extreme high temperature at panicle initiation and flowering stage. The reduction in grain yield at sowing date May15in comparison with June4was higher for the Bt-transgenic rice lines. MH63(1C*) had significantly lower grain yield than MH63at all the three sowing dates, while MH63(2A*) had significantly higher grain yield than MH63when sown at June4. There were changes in leaf number, panicle development and tillering between MH63(1C*), MH63(2A*) and MH63.(3) Grain yield of NO treatment was significantly lower than that at N1and N2due to the lower grain filling percentage in2009, while there was no significant difference in grain yield among the three N treatments in2010. Hybrid varieties (lines) had significantly higher grain yield than three restorer lines. MH63(2A*) had significant higher grain yield than MH63when195kg N ha-1was applied, In2010, the three hybrids utilized N more efficiently than the three restorers. MH63(1C*) had significantly lower NUEg and NHI than MH63(2A*) and MH63.(4) There were three K treatments in2009, namely0,45and135kg ha-1. Grain yield and KUEg at135kg ha’1were significantly lower than that at0and45kg ha-1. No significant difference was found in K accumulation in stem and grain between Bt-MH63and MH63at maturity. K concentration in stem were similar for Bt-MH63and MH63, but MH63(2A*) had significantly higher K concentration in grain than MH63. KUEg was significantly lower for MH63(1C*) and MH63(2A*) than MH63when0and45kg ha"1were applied.(5) Damage caused by leaffolders became severe when N fertilizer rate increased. No. of larva per100hills increased from400to1200when N fertilizer rate increased from0to210kg N ha1. Grain yield of SY63(1C*), SY63(2A*) and SY63at N rate of210kg N ha"1was lower than that at90and150kg N ha"1. Incorporation of crylC*and cry2A*into the genome of rice could control leaffolders efficiently, and the efficacy of cry1C*was better than cry2A*. The yield advantage of SY63(1C*) and SY63(2A*) over SY63was all around20%, but they were achieved at different N fertilizers rates. The content of Bt protein in the leaf significantly correlated with N content.(6) In conclusion, the incorporation of Bt genes into rice genome lead to effective control of target insects, and there was variation in the efficacy for different Bt genes. Under free insect condition, Bt transgenic rice showed variation in agronomic and physiological traits in comparison with control, but the change was not consistent for different Bt transgenic rice. |
