Six cycles of S1 recurrent selection in two Spanish maize synthetics

European flint × U.S. dent is the most common heterotic pattern used in early maize (Zea mays L.) breeding programs in Spain. Two synthetic maize populations, EZS1 (formed from four Spanish flint populations), and EZS2 (formed from four American dent populations), were developed in Zaragoza, Spain. These synthetics, which showed heterotic behaviour, were subjected to six cycles of S1 recurrent selection for increased grain yield and reduced lodging. The aim of this study was to investigate the effectiveness of selection on these and other agronomic traits in both synthetics. The original populations, EZS1C0 and EZS2C0, and the six cycles of selection of both, were evaluated at two locations over two years. Over the six selection cycles, the average yield of EZS1 and EZS2 increased by 0.82 Mg ha and 0.93 Mg ha per cycle respectively, while lodging decreased by 2.76% and 2.44% per cycle respectively. Changes due to selection were significant for all test traits in both synthetics. It was concluded that S1 selection is effective in improving the yield of, and reducing lodging in, both synthetics. Additional key words: heterotic pattern, local populations, recurrent selection, Zea mays L.