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Selection for Early Flowering in Corn: 18 Adapted F₂ Populations

I measured selection-for-early-flowering effect during corn(Zea mays L.) inbred line development on hybrid performance in two experiments of adapted F₂ populations. The first experiment studied eight F₂ populations from 11 inbreds; the second experiment studied 10 F₂ populations from all possible two-way crosses of five elite, unrelated, proprietary inbeds. I selected the earliest flowering 11 or 12 plants (2%) of 550 to 600 plants per F₂ population grown at 87 000 plants ha_–1 and intercrossed them with bulked pollen for two cycles, then selfed the third cycle of selection grown at 105 000 plants ha^–1. I random sib-mated within populations after Cycles 1 and 2. The first experiment's materials were crossed to Iowa inbred B14, then tested at two densities in 1 yr. Selection effect per cycle averaged: 0.6 day less to flower, 0.6 percentage points less grain moisture, 2.4 cm less plant height, 0.1 day less silk delay, 364 kg ha_–1 (6%) more yield, and no stalk breakage effect. The second experiment's materials were crossed into the 15 possible unrelated four-way crosses among populations within cycles, then tested at three densities in 2 yrs. Selection effect per cycle averaged: 1.2 day less to flower, 1.0 percentage point less grain moisture, 7.0 cm less plant height, 0.1 day less silk delay, 238kg ha^–1 (4%) less yield, 0.5 more ears 100^–1 plants, and 3.7% more stalk breakage. All possible four-way crosses measured selection effect well, but measured inbred-lines parent effects poorly.Several important agronomic traits improved during inbred development via selection for early flowering.

Key Words: Genotype x tester interaction • Genotype x year interaction • Inbred line development • Phenotypic recurrent selection • Population improvement • Simple recurrent selection • Zea mays L.

Received for publication May 13, 1985.