Dissecting of the Deterioration in Eating Quality for Erect Panicle (Ep) Type High Yield Japonica Super Rice in Northest China
Abstract Ep type is an important morphological improvement (following dwarf breeding and ideal plant type) to adapt to super high yield breeding of rice, which shows a pleiotropic effect in increasing grain yield and nitrogen use efficiency (NUE) in rice. Nevertheless, it remains unclear whether Ep has adverse effects on eating quality and its regulatory of increasing nitrogen uptake and assimilation. In this study, we developed a pair of near-isogenic lines (NILs) of dep1 (NIL-Ep, NIL-Non Ep) in the Liaogeng 5 (LG5) and Akihikari (AKI) backgrounds. Here, we report that rice plants NIL-Ep have more grain numbers per panicle in middle to bottom spike positions than plants NIL-non Ep. This part of increased grain not only is the key factor to increase the yield, but also is the reason to reduce the eating quality. The content of prolamin and glutelin in the grain increased significantly, which resulted in higher hardness and worse viscosity of rice after cooking. Additionally, the activity of several essential enzymes catalyzing nitrogen metabolism is higher in the NIL-Ep line than in NIL-non Ep line, especially from the mid to late grain filling stage. Based on these results, we conclude that Ep positively regulates grain protein accumulation primarily through enhance the activity of enzyme enroll nitrogen assimilation and redistribution during the mid to late grain-filling stage, resulting in excessive accumulation of grain protein and decreased the quality of eating.