Heterosis among populations of maize (Zea mays L.) with different levels of exotic germplasm.
Thirteen maize (Zea mays L.) populations including five adapted, five adapted x exotic, two composites of adapted and exotic, and one exotic selected for adaptability were crossed in a diallel mating system. The parents and 78 crosses and nine check hybrids were evaluated for grain yield and plant height in five environments. The Gardner-Eberhart model Analysis II indicated that additive and nonadditive gene effects accounted for 60 and 40% of the total variation among populations, respectively, for grain yield and 86% and 14% of the total variation, respectively, for plant height. Components of heterosis were significant in the combined analysis for both traits. Adapted Corn Belt populations tended to have higher performance in crosses and greater values of variety heterosis than 50% adapted populations. 'Nebraska Elite Composite', 'Corn Belt' x 'Mexican', and 'Corn Belt' x 'Brazilian' showed high mean yields in crosses, however, they were not among those with high estimates of variety heterosis. One exotic population ('Tuxpeno' x 'Antigua Grupo 2') and three adapted populations ['307 Composite', 'NB(S1)C-3', and 'NK(S1)C-3'] might be combined together to form a high-yielding population. It may be possible to synthesize two useful populations for reciprocal recurrent selection by grouping 'Tuxpeno' x 'Antiqua Grupo 2', 'NB(S1)C-3', and 'NS(FS)LFW-8' into one population and 'NK(S1)C-3', 'Krug'x'Tabloncillo', and '307 Composite' in the other one.
International Center for Maize and Wheat Improvement (CIMMYT), Apartado Postal 6-641, 006600, Mexico DF, Mexico.
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