Breeding Potential of European Flint and Earliness‐Selected U.S. Corn Belt Dent Maize Populations

Abstract

Flint × dent maize (Zea mays L.) hybrids are commonly planted in the early corn growing regions of Europe (northern and the Atlantic Coast of Europe). Evaluation of the early maize germplasm is important for the development of new commercial hybrids adapted to cooler summer regions. Our objectives were to assess the potential of flint and earliness‐selected dent germplasm as base populations for developing early grain maize hybrids and to determine the performance and heterosis of this germplasm. Eight populations formed the base material of this study. Four populations were U.S. Corn Belt dent populations that had undergone several cycles of selection for earliness. The other four were European early flint populations. The eight populations, their diallel crosses, and topcrosses to inbreds A632 and EC18 were evaluated at five environments in northwestern Spain in 1991 and 1992. Dent populations outyielded Hint populations by 220 g kg−1 at the per se level, by 100 g kg−1 when crossed to flint and dent inbred testers, and by 50 g kg−1 in the population diallel crosses. The yield heterosis of population crosses was 26% of the population yield mean. The dent germplasm exhibited less stalk and root lodging than flint germplasm. When yield and other agronomic traits are globally considered, the earliness‐selected dent populations seem best for the development of hybrids to be grown in mild summer environments. Because specific dent germplasm is being developed for early areas, it seems that dent × dent commercial hybrids should progressively replace flint × dent hybrids in the early maize growing regions of Europe.