Effects of Phosphorus Application Rate on Lipid Synthesis and Eating Quality of Two Rice Grains

Abstract

Lipids are an important nutritional component of rice, and lipid content has an important effect on rice eating quality. However, the effects of the fertilizer application rate on lipid synthesis and eating quality of rice are poorly understood. To investigate the effects of phosphorus (P) fertilizer on lipid synthesis and eating quality of rice, we used Nanjing (NJ) 9108 (japonica) and IR72 (indica) rice as experimental materials, and four P levels, P0 (0 kg ha−1), P1 (45 kg ha−1), P2 (67.5 kg ha−1) and P3 (135 kg ha−1). The results showed that the lipid, free fatty acid (FFA) content, unsaturated fatty acid (UFA) content, malonyl-CoA (MCA) content, phosphatidic acid (PA) content, lipid synthesis-related enzyme activities and eating quality of both cultivars increased with increasing P. However, the saturated fatty acid (SFA) content showed the opposite trend. No significant differences were found in pyruvate (PYR) content between P treatments. Protein and oxaloacetic acid (OAA) contents and phosphoenolpyruvate carboxylase (PEPCase) activity first increased and then decreased with increasing P, which indicated that high P levels could stimulate lipid synthesis more than protein synthesis. Overall, increasing P optimized fatty acid components and increased the lipid content and eating quality of rice by enhancing lipid synthesis-related enzyme activities and regulating substrate competition for lipid and protein synthesis. The optimal P application rate for lipid synthesis and eating quality of both cultivars was 135 kg ha−1.