Variation and Covariation in a High Oil Population of Corn (Zea mays L.) and Their Implications in Selection1

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Abstract
Sixty‐four half‐sib families, each containing four full‐sib families, were grown in replicated trials in five environments. Data were collected for silking date, plant and ear heights, kernel size, lodging percentage, shelling percentage, oil percentage, yield of grain, and yield of oil. Estimates of additive and dominance variances were calculated for each trait, and these variance estimates were used to predict the genetic gain from different selection methods. Phenotypic and additive genetic correlations among traits were calculated.All estimates of additive genetic variance were significantly greater than zero. None of the estimates of dominance variance was significant except for yield of grain in one environment. Mass selection appeared to be the most effective method of selection for higher oil percentage in this population, but recurrent selection for general combining ability would be the most effective method for yield of grain and yield of oil. The only traits significantly correlated with oil percentage were silking date and yield of oil. A selection index for improving yield of oil appeared to have little advantage over selection for yield of oil alone.