Recurrent selection for grain yield in two Spanish maize synthetic populations

The most common maize (Zen mays L,) heterotic pattern in Europe is European flint x U.S. dent. Northern Spain x southern Spain has been proposed as an alternative heterotic pattern. Three maize synthetic populations, namely E PS6 from northern Spain, EPS7 From southern Spain, and EPS10 formed by earl y American populations, were produced in Pontevedra, Spain. Because of thei r low yield, the two Spanish synthetic populations were subjected to three cycles of intrapopulation S-1 recurrent selection for grain yield. Our obje ctives were to evaluate the effect of selection on grain yield and other ag ronomic traits, and to determine the changes in heterosis and general (GCA) and specific (SCA) combining ability brought about by selection. The three original synthetic populations, the three cycles of selection of the two S panish synthetic populations, and the crosses among the original and the im proved cycles were evaluated in two locations in northwest Spain in 1994 an d 1995, Yield significantly increased with selection in both Spanish synthe tic populations. The GCA improved with selection in both EPS6 and EPS7, Het erosis and SCA did not change significantly with selection. The third cycle s of each Spanish synthetic would be the most appropriate maize populations to start a reciprocal recurrent selection to improve the heterotic pattern northern Spain x southern Spain.