IRRIGATION MANAGEMENT RISKS AND ZN FERTILIZATION NEEDS IN ZN BIOFORTIFICATION BREEDING IN LOWLAND RICE
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As zinc (Zn) fertilizer and water management affect the expression of Zn-enriched grain traits in rice, we studied the effect of Zn fertilizer and water management on Zn uptake and grain yield of different biofortification breeding lines and the possible biases in selection for high grain Zn content. The first field experiment showed that longer duration genotypes had higher grain Zn uptake rate than shorter duration genotypes during grain filling. In the first greenhouse experiment, neither application of Zn fertilizer at mid-tillering nor application at flowering significantly increased the grain Zn concentration. In the second greenhouse experiment, application of alternate wetting and drying (AWD) significantly increased the available soil Zn and plant Zn uptake but not grain Zn concentration. Terminal drying (TD) did not increase the available soil Zn or grain Zn contents. The second field experiment confirmed that differences in TD were not important in understanding differences between genotypes. Zn application is not always necessary to breeding trials unless there is a severe Zn deficiency and there is no need to carefully regulate TD prior to harvest.
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