Use of Rapid Cycle Recurrent Selection method for grain zinc and yield enhancement in rice
2024
Punzalan, J.C.
Rapid Cycle Recurrent Selection (RCRS) was used to evaluate a 1-year breeding cycle's effectiveness in enhancing genetic grain zinc content (Zn sub GC) and yield. This study started by optimizing the 1-year cycle, simulating the breeding method, validating new purity markers, and employing X-ray flourescence handheld (XRFh) for phenotyping. Among-family selection (AFS) yielded an initial highest response of 7.69% (Zn sub GC) and 7.58% (yield) in the first 5 cycles after the 1st cycle, outperforming among within-family selection (AWFS)at 6.42% (Zn sub GC)and 6.99% (yield) and within-family selection (WFS) at 4.07% (Zn sub GC) and 4.16 (yield). To fit all activities within a year, overlapping sowing of testing and crossing, and utilization of XRF were implemented. Desired index (DI) in Cycle 0 (C0) was used to improve these two highly negatively correlated traits (-0.55) by assigning 1.5(Zn sub GC) and 1.0 (yield) selection differential as economic weights. The realized gains from C0 to C1 were 4.90% and 7.53% for Zn sub GC and yield, respectively. For C2, single nucleotide repeat (SNP) scores were generated by simulating allele inheritance during a generation of selfing, and crossing using sequence of selected C1 S0.1 lines. Based on the mean simulation runs gains of 3.99% and 2.53% relative to the C1 mean performance are predicted to be achieved. Remarkably, both genetic and genomic additive variances in both traits increased from C0 to C1. Overall, RCRS demonstrates the effectiveness of implementing a 1-year breeding cycle and DI in delivering a high rate of genetic gain despite a negative correlation traits.
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