Non-target effects of Bt transgenes on grain yield and related traits of an elite restorer rice line in response to nitrogen and potassium applications

• Bt-MH63 and MH63 (Oryza sativa L.) differ in response to N and/or K applications.
• MH63 (Cry1C*) had weaker flow traits in physiological function and morphology.
• Yield changes of MH63 (Cry2A*) were related to the higher Bt protein expression.

Using a transgenic Bacillus thuringiensis (Bt) crop is reportedly one of the most effective ways to improve insect resistance; however, the insertion of external Bt genes may affect the non-target growth characteristics of crop. Field experiments were conducted to investigate the yield performance and physiological traits in an elite restorer rice line, Minghui63 (MH63) with Cry1C*, Cry2A* or Cry1Ab/Ac genes under three fertilizer applications [zero nitrogen fertilizer (N0), zero potassium fertilizer (K0) and recommended nitrogen and potassium fertilizer (NK)]. In comparison with MH63, MH63 (Cry1C*) experienced declining grain yields of 15.3–31.0% under different fertilizer applications because of the decreased setting rates associated with the poorer matter transport-related traits. The grain yield of MH63 (Cry2A*) was averagely 18.4% lower than MH63 in only the N0 treatment due to the accelerated leaf senescence, which was correlated with the higher ratios of the Bt protein content to the soluble protein content (BTC/SPC) in the MH63 (Cry2A*) leaves at the filling stage (FS). The yield performance of MH63 (Cry1Ab/Ac) was identical to MH63. In addition, no significant differences were recorded between Bt-MH63 and MH63 regarding N and K assimilation. Hence, our results suggest that the Cry1C* and Cry2A* transgenes affect the yield performance and related traits of MH63 in response to nitrogen and/or potassium applications.