Responses to S1 Selection in Flint and Dent Synthetic Maize Populations
- G. Garay,
- E. Igartua and
- A. Alvarez
Flint × dent is a common heterotic pattern exploited in maize (Zea mays L.) breeding programs across Europe. Two maize synthetics, EZS1, a mixture of Spanish open-pollinated flint varieties, and EZS2, crosses among North American dent-improved populations, were produced in Zaragoza, Spain. The synthetics showed heterotic behavior and were subjected to two cycles of S1-progeny intrapopulation selection for grain yield and lodging resistance before starting reciprocal recurrent selection. Our objectives were to partition the response to selection into additive and dominance effects after two cycles of intrapopulation selection, with generation mean analysis and diversity analysis. The entries resulting from a diallel mating design, without reciprocals, among the original and first two cycles for each population, were tested in five environments. The results showed that both populations were responsive to selection for improved grain yield, but only EZS2 was improved by selection against lodging. Diversity analysis was less conservative than the generation means model in detecting significant genetic effects. Genetic effects associated with selection for grain yield and lodging were mostly additive, but a significant dominance effect was detected in EZS2 for lodging. The improvement of the population cross did not match that of the populations per se, especially for EZS2. A loss of heterosis for the cross was detected, which might become unrecoverable if S1 selection is continued. It was concluded that S1 selection should be discontinued and that reciprocal recurrent selection should be initiated.
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