Earlier experiments have shown that the perennialism of Zea diploperennis as expressed by the occurrence of rhizomes is more nearly recessive than dominant. In F1 hybrids grown in three localities in Argentina no true rhizomes occurred, but "bulbils," highly-condensed rhizomes, were found. In a selfed population of 64 plants resulting from backcrossing this F1 hybrid twice to corn (7/8 corn), no rhizomes occurred but two plants had tillers arising from below ground level, presumably from bulbils. Thus one expression of perennialism, the occurrence of rhizomes, is definitely recessive. In this respect, our results agree with those of Shaver (J. Hered. 1967), who found perennialism derived from the tetraploid perennial teosinte to be recessive and to be expressed only in the presence of two other recessive genes, id for indeterminate growth and gt for grassy tillers.
The perennialism derived from Zea diploperennis has additional expressions: evergreen stalks (Galinat MNL, 1981), stiff stalks, and robust root systems including adventitious roots. Whether these represent various expressions of the same gene or those of a cluster of closely linked genes has not been determined.
Shaver assigned the symbol pe to the recessive gene isolated from Z. perennis. We would like to assign the symbol Pe to the perennial gene isolated from Z. diploperennis. At the suggestion of Dr. Coe we are using the designation Pe*-d to distinguish it from the gene isolated from perennis.
The combination of evergreen stalks, stiff stalks and robust root systems is strongly, but not completely, dominant since plants homozygous for the gene can be distinguished from the heterozygotes in our cultures. In this population the homozygotes are almost completely sterile.
Paul C. Mangelsdorf and Mary Eubanks Dunn
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