The pleiotropies associated with recessive alleles have now been characterized for ten different recessive alleles in the Oh43 - recessive allele x Oh551 hybrid combination. Of the ten recessives, three increased grain yield in the hybrid. (Increases of 3%, 4%, and 11% respectively.)

The lty1-16 recessive increased grain yield by 3% in the Oh551 hybrid combination. Preliminary studies were conducted to determine if the lty1-16 allele would increase grain yield in other hybrid combinations. Grain yields were increased in two other hybrid combinations (increases of 5% and 7% respectively) and not in three combinations. The pleiotropy affecting grain yield appears to be turned on or off in specific hybrid backgrounds. (Incidentally, this type of gene action may explain how phenotypic traits skip generations in a family pedigree.)

Many inbred plants homozygous for a specific recessive allele are as vigorous as the normal inbred plants. Thus, the production and selection of recessive mutant alleles in an inbred line and their testing in various hybrid combinations provides an effective method for increasing grain yields in maize hybrids.

E. J. Dollinger

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