Abstract
Understanding Zn uptake dynamics is critical to rice grain Zn biofortification. Here we examined soil Zn availability and Zn uptake pathways as affected by genotype (high-grain Zn varieties IR69428 and IR68144), Zn fertilization and water management in two pot experiments. Results showed significant interactions (P < 0.05) between genotypes and Zn fertilization on DTPA (diethylenetriaminepentaacetic acid)-extractable soil Zn from early tillering to flowering. DTPA-extractable Zn in soils grown with IR69428 was positively correlated with stem (r = 0.78, P < 0.01), flagleaf (r = 0.60, P < 0.01) and grain (r = 0.67, P < 0.01) Zn concentrations, suggesting improved soil Zn availability and continued soil Zn uptake by IR69428 even at maturity. Conversely for IR68144, DTPA-extractable Zn was positively correlated only with leaf Zn uptake (r = 0.60, P < 0.01) at active tillering, indicating dependence on remobilization for grain Zn loading. Furthermore, the highest grain Zn concentration (P < 0.05) was produced by a combination of IR69428 and Zn fertilization applied at panicle initiation (38.5 μg g−1) compared with other treatments (P < 0.05). The results highlight that Zn uptake behavior of a rice genotype determines the fate of Zn from the soil to the grain. This has implications on overcoming Zn translocation barriers between vegetative parts and grains, and achieving grain Zn biofortification targets (30.0 μg g−1).
Highlights
Understanding Zn uptake dynamics is critical to rice grain Zn biofortification
The present study noted results from Wissuwa et al.[4], who concluded that grain Zn concentration is largely determined by genotype rather than by Zn fertilization, which could be attributed to differences in Zn uptake behavior
Our results demonstrated that DTPA-extractable soil Zn concentrations were altered by genotype in addition to water management (WM) and ZF
Summary
Understanding Zn uptake dynamics is critical to rice grain Zn biofortification. Here we examined soil Zn availability and Zn uptake pathways as affected by genotype (high-grain Zn varieties IR69428 and IR68144), Zn fertilization and water management in two pot experiments. Tuyogon et al.[10], who used both IR68144 and IR69428 in field experiments, observed a significant increase in DTPA-extractable soil Zn and grain Zn uptake in longer-duration genotypes as a result of water management (WM), such as by alternate wetting and drying (AWD) These authors concluded, that the effect of AWD on grain Zn concentration was still minimal and the effect of Zn-fertilization (ZF) timing on grain Zn accumulation was not significant. These suggest that drying events and ZF should be optimized to correspond with the crop demand for Zn, during grain Zn loading, which may vary among rice genotypes. Reports remain limited in relation to genotype variations in Zn uptake pathways
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