Department of Plant Sciences

Iron (Fe) is an important essential micronutrient and its deficiency is a widespread micronutrient malnutrition problem for human being in the world. Iron biofortification of staple food crop is regarded as an effective way to solve this problem. Rice is the most important food crop in the world feeding over half of the global population; therefore, a small increase in Fe concentration in rice grain can greatly improve human health. However, the mechanisms of Fe dense accumulation in rice grain are not fully understood, which limits the advance of high Fe-dense rice breeding. In this paper, the characteristics of Fe re-utilization in the dense rice genotype (IR68144) were studied, as compared with the indense rice genotype (IR64). The results showed that the ability of iron remobilization from “source” to “sink” was much greater in IR68144 than in IR64, i.e. from root, the 1st, 2nd, and 3rd leaf, as well as leaf sheath to the new growing leaves and tillers at vegetative stage, and from root, stem, and flag leaf to grain at reproductive stage. It was estimated that the re-mobilization of Fe in the dense genotype IR68144 accounted for 28.5% of total Fe of the plant at the 4th leaf stage, which was 1.6-fold higher than that of the in-dense genotype IR64. At the reproductive growth stage, the re-translocation of Fe from leaves and stems to grain was found to be much greater in the dense than in the indense rice genotype, and the re-translocation of Fe depended greatly on Fe pretreatment levels before anthesis and Fe/Zn nutritional status after anthesis. The dense genotype remobilized about 10-time more Fe from stem with low Fe pretreatment, and exported around 6-time more Fe from roots and 10-time more Fe from the flag leaf with adequate Fe pretreatment, as compared to the indense genotype. The remobilization of Fe from the vegetative organs to grain was greater at low Fe supply than at higher Fe supply, and greater re-translocation of Fe was noted in IR68144 than in IR64 when pretreated with low Fe. After stopped Fe supply at anthesis, the Fe export from the flag leaf decreased with increasing Fe pretreatment levels in IR68144, but Fe input in the flag leaf was noted in IR64. After anthesis, the contribution of remobilized Fe to brown rice Fe accumulation was greater in IR68144 than in IR64 with low, adequateand high Fe pretreatments. The results indicate that the Fe-dense rice genotype has greater ability of reutilizing Fe in the source tissues than the indense genotype, and the remobilization ability of Fe from older leaf to the new growing leaves could be used for predicting grain Fe accumulation ability.