19. Vestigial glume (Vg) and Tunicate (Tu). The two dominant genes Vg (Sprague, 1939) and Tu (Collins, 1917) have opposite effects on the length of the glumes in both the staminate and pistillate inflorescences of maize. Vestigial glume, as the name implies, exposes the anthers and removes most of the glumes from the ear; whereas Tunicate incloses the anthers in long glumes and the individual kernels in husk-like structures. In view of these differences, would a plant with the genetic constitution Vg be like Yg? or Tu? or neither of them? In the progeny of a cross of Vg/vg × Tu/tu four types of plants were observed:

Phenotype (length of glumes)  
Staminate Inflorescence Pistillate Inflorescence Probable Genotype
Vestigial Long like Tu, but more narrow Vg vg Tu tu
Vestigial Vestigial Vg vg tu tu
Tunicate Tunicate vg vg Tu tu
Normal Normal vg vg tu tu

Since ordinarily the length of the glumes in the tassel is directly correlated with the length of those on the ear, it is difficult to explain why, in plants with the genetic constitution vg vg Tu tu, Vg shows epistasis to Tu in the tassel and not on the ear. It has been noted, however, that some times plants heterozygous for Tu do not have exceptionally long glumes in the tassel. Perhaps there is an upper limit to the length of glume that is able to reduce to a miniature size. Further tests should be made to note the appearance of plants with the genetic constitutions Vg Vg Tu Tu, Vg Vg Tu tu, and Vg vg Tu Tu. This material would not be easy to obtain as plants homozygous for Tu are usually male and female sterile. Likewise, Vg Vg plants are difficult to produce as Vg vg must be grown under very favorable greenhouse conditions to obtain viable pollen.

D. G. Langham, Estacion Experimental, El Valle, D. F. Venezuela