Two dominant mutations in maize, vestigial glume (Vg1) and tunicate (Tu1), affect the same plant part (glumes) but in opposite ways. In vestigial glume, the glumes are much reduced in both the male and female inflorescence. In addition, the vestigial glume mutant is liguleless.
Tunicate, on the other hand, greatly increases the size of glumes on both the male and female spikelets resulting in complete encasement of kernels. The ligule is not affected.
A double heterozygote of vestigial glume and tunicate was constructed to find how these two mutations interact. The phenotype of the double heterozygote is intermediate between the two extremes exhibited by either mutation but is still quite different from the normal plant phenotype. On the ear, Tunicate seems to have the upper hand. The kernels are still half to fully covered depending upon where they are on the ear. Kernels near the butt of the ear have larger glumes than the kernels located near the tip of the ear. In tassels, the effect of vestigial glume seems to dominate. The glumes are about half the size of wildtype and, as a result, the anthers tend to protrude out of the spikelets. In contrast, the ligule is completely suppressed in the double mutant. Clearly, these mutations are antagonistic to each other only in the inflorescence and the action of Tu1 appears to be restricted to the inflorescence. To gain further insight into this interaction, stocks containing different doses of tunicate and vestigial glume are being constructed.
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