Zinc Biofortification of Selective Colored Rice Cultivars: Improvement of Zinc Uptake, Agronomic Traits, and Nutritional Value

It is difficult for ordinary rice to break the zinc-rich standard. However, employing multiple unique rice cultivar resources through biofortification of agronomic measures to achieve the target is a promising attempt. In this study, a pot experiment was conducted on seven different colored rice cultivars (GFHN 166, GFHN 168, GFHN 169, GH 1, GXHZ, GHSZ, and YXN), aiming to analyze the effect on zinc content, growth, quality, and health risk index when spraying zinc (400 g/ha) on the leaves at the heading age. The result indicated that after foliar biofortification treatment, the zinc content and the zinc accumulation of colored rice grains could reach up to 41.55 mg/kg and 2.28 mg/pot, respectively, increased by 43.92% and 65.22%. In addition, the SPAD value and grain protein content was 42.85 and 8.49%, also increased significantly by 2.15% and 2.91%, respectively. Among these, GXHZ and GHSZ could realize the zinc content of polished rice up to 69.7 mg/kg and 55.4 mg/kg, breaking through the standard of zinc-enrich rice (45 mg/kg). GXHZ plant height increased by 11.22%, and the zinc harvest index (6.44%) and zinc use efficiency (26.79%) were the highest. Meanwhile, the biofortification promoted the SPAD value of GHSZ and the protein content of GFHN 166 by 4.95% and 24.81%, respectively. Foliar-applied zinc at the heading stage is a vital practice to get better agronomic indicators, quality, and grain zinc biofortification of colored rice.