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The study of cytoplasmic effects on the expression of agronomic characters is important in learning about cytoplasmic‐nuclear interactions and their influence on breeding and genetic programs. The genotype of the longtime maize (Zea mays L.) inbred, GT 112, was backcrossed six or seven times into three cytoplasms other than its own. Thus, each cytoplasmic source of seed was assumed to have the same nuclear genotype.The four cytoplasms, studied previously in a double‐cross hybrid, were compared in inbred GT 112 in all possible combinations for 2 years with 10 replications per year. Significant differences among the cytoplasms occurred for germination, number of dead seedlings due to Fusarium sp., diseased plants, plant vigor, color, leaf rolling, date of tasseling and silking, plant and ear heights, yield, and grain quality.Certain combinations of cytoplasm and inbred genotype gave more desirable performances than others under certain environments. There was a significant or highly significant interaction for year ✕ cytoplasm within pairs for all of the characters tested 2 years except for germination and number of plants before thinning.Results from these experiments provide further support for cytoplasmic effects on agronomic characters in maize. They also emphasize that the environment can influence the performance of a cytoplasm from one year to another.

Synopsis Significant cytoplasmic effects were obtained in a double‐cross maize hybrid for the agronomic characters: yield, silking, ear and plant heights, erect plants, and budworm damage. All cytoplasms did not interact with the genotype in the same manner. These results apparently justify consideration of the source of cytoplasm in a breeding program. In most cases when differences occurred between the cytoplasmic effects, the performance of the hybrid was in the direction of the inbred performance.