Response to Full‐Sib Selection in Four Medium Maturity Maize Populations1

Abstract

The International Maize and Wheat Improvement Center uses full‐sib (FS) family selection based on internationally replicated trials to improve several tropical maize (Zea mays L.) populations. Improvements made in four medium maturity tropical maize populations are reported here. Selection from CO to C1 in ‘ETO Blanco’ (EB) and ‘Antigua‐Republica Dominicana’ (ARD), and from C0 C2 in ‘Blanco Cristalino‐l’ (BC) and ‘Mezcla Amarilla’ (MA), involved formation of 250 FS families in one season, and their evaluation in three to six environments in the second season in a 16 ✕ 16 simple lattice design using 40% selection intensity. Additional cycles of selection involved selection among and within FS families using a 2‐yr four‐season system; evaluation and selection of families were done as above, superior S1 plants of the selected FS families were bulk‐sibbed, and the resulting half‐sib families used to develop FS families for subsequent cycles of selection. The C0, C2, and C5 of BC and MA, and CO, C1, and C4 of EB and ARD were evaluated in seven environments to measure progress from selection. Gains per cycle (%) averaged over populations and environments for yield, days to silk, plant height, ear height, ear rating, and ears per plant were 2.11** (significant at the 0.01 probability level), −0.31**, −0.26**, −0.47**, −1.35**, and 1.05**, respectively. The regressions of entries on environmental means generally did not differ significantly from 1.0, indicating stability in the performance of the materials for yield, days to silk, and plant height. Our results indicate that FS selection is an effective method to improve tropical maize populations for the six traits studied.