Combined Half-sib and S1 Family Selection in a Maize Composite Population1
- Christos K. Goulas2 and
- J. H. Lonnquist3
Recurrent selection for intrapopulation improvement in maize (Zea mays L.) using combined HS-S1 progeny evaluation was studied. The source population (3-L Composite) originated from three inbred lines (W64A, W182E, A635). The F2 generations of the three possible single crosses were planted in an isolated plot. At flowering time, ear shoots were covered on prolific plants. The lower ear was self-pollinated to provide Si seed and the upper ear exposed to open-pollination to provide half-sib (HS) seed. Half-sib and S1 progenies were evaluated in separate trials using incomplete blocks of 10 entries each with two replications. Selection was carried out on a per block basis. Plants with superior HS and S1 progeny performance, i.e., above average yield and equal or below average moisture in the grain at harvest in both trials, were selected. Selection intensity was 22 and 20% in CO and Cl, respectively. Each new cycle was initiated from remnant HS seed. Two selection cycles have been completed. The estimated degree of inbreeding was 34% in CO, 43% in Cl, and 44% in C2. Relative to CO, selection resulted in 5% yield improvement in Cl (based on 3-year testing) and 20% improvement for C2 (2-year tests). Also, Cl was 1 day earlier to flower, taller with slightly higher (103%) ear placement, and had less moisture in the grain at harvest (97%). C2 exhibited no further change for moisture in grain at harvest but was taller, ear height being 111% relative to CO. Thus far, selection has reduced inbreeding depression in the population without decreasing heterosis for yield in HS families.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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