Do Second Cycle Maize Inbreds Preserve the European Flint Heterotic Group?

Abstract

Knowledge of heterotic patterns is essential in hybrid maize (Zea mays L.) breeding programs. Second cycle inbreds of maize were developed from crosses between three historical European inbreds (EP1, F2, and F7) and American or European germplasm. The objective of this study was to find out if the second cycle inbreds derived from EP1, F2, and F7 preserved the European flint heterotic group. Crosses of first and second cycle inbreds with four testers (W64A, A619, A632, and W117) were evaluated in northwestern Spain. Second cycle inbreds from EP1 or F2 × European germplasm had the highest yield and early vigor in crosses to the testers, probably because flint × dent heterosis was preserved. The U.S. germplasm used to develop second cycle inbreds from EP1 and F2 included germplasm from the open‐pollinated variety Minnesota No. 13. The use of Minnesota No. 13 germplasm to develop second cycle inbreds from crosses to European flint should be avoided because almost all the early U.S. Corn Belt dent inbreds introduced into Europe are related to Minnesota No. 13. ‘Lancaster’ germplasm was suitable to improve the yield of F7, but this material lacked early vigor. Lancaster‐related second cycle inbreds performed better for yield than the ‘Reid Yellow Dent’ because two testers were of Reid origin. The highest early vigor was obtained for second cycle inbreds from F7 × European inbreds. European flint germplasm is appropriate for improving European inbreds in crosses to U.S. germplasm, whereas the U.S. germplasm may be used to improve a specific cross.