Additional studies were conducted with the CI 21 (Athens) inbred to evaluate the effects of nuclear-cytoplasmic interactions on agronomic characters within inbred and also to evaluate the best combination of cytoplasm and genotype on the basis of inbred per se.

Inbred CI 21 (Athens) was prepared with the following cytoplasms: GA 199 and GT 112. Each source of cytoplasm as the female parent was crossed to the CI 21 (A) as the pollen parent. The F1, as the female, was backcrossed successively to the CI (21) genotype until the CI 21 (A) nucleus was totally substituted into each of the cytoplasms.

The cytoplasms were tested in paired comparisons. Among the characters studied, significant differences were obtained for effect of herbicide, reaction to Fusarium sp., northern leaf blight of corn, silking on a given day, tasseling, plant height, ear height, lodging and number of ears.

These results revealed a favorable interaction of GA 199 cytoplasm with the CI 21 (A) genotype for desirable characters. Apparently plasmon-sensitive effects and plasmagenic-environmental effects caused the unfavorable results.

A. P. Rao and A. A. Fleming

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