C - Hybrids between teosinte and "São Paulo Corn" - Hybrids were produced between teosinte and heterozygous "São Paulo Pod" corn, consisting of tunicate and non-tunicate plants.

The tu plants in F1 corresponded as a whole with the descriptions given by other authors, and we shall withhold discussion until the analysis of F2 and backcrosses, now under way, are terminated.

The F1 tunicate plants, however, showed many unexpected characteristics, some of which only will be mentioned here:

The Tu effect on the tassel was completely recessive-hypostatic and it was impossible to classify the F1 plants as in the original "São Paulo Pod" according to the transformation of the tassel. Thus the tassels of Tu plants and their normal tu sisters were identical.

The ears, however, were very different in Tu and tu hybrids. In the rows were mainly single, or when the paired row was not suppressed, they contained female spikelets only. Two paired rows appeared generally in the Tu plants, one being an ordinary female spikelet, with one sterile and one female flower, while the other spikelet became pedicelled and contained two male flowers. Furthermore, there was a pronounced tendency to produce not only 2 double rows, but 3 or even 4.

The scales formed by the rachis and which cover more or less the grains in teosinte or in tu F1 plants, were smaller and soft in Tu plants while the glumes became pointed.

The rachis and glumes of the tu hybrids are extremely horny, and it was very hard work to shell the seeds. On the other side, the rachis in Tu F1 plants is extremely brittle and it was nearly impossible to harvest complete mature ears, since they fell apart immediately after removing the shucks.

Thus the Tu gene has a very different phenotypic effect in pure corn and in teosinte-corn hybrids. In the former we observe a pronounced tendency to introduce femaleness into the tassel, while in the latter maleness appears in the ears, or better on the lateral branches. A selection experiment is under way with the end of fixing this condition, just as it was possible to fix more or less the bearded tassel.

The fact that the Tu-gene acts in nearly opposite directions according to the modifier complex present, should warn us not to draw premature conclusions on gene action. The appearance of covered kernels is a universal effect of the Tu gene, while everything else depends upon the modifier back-ground. The Tu F1 plants described above seem to me much more likely to be a replica of an ancestral wild grass than the Tu corn plants with bearded tassel, especially considering the following points: a) the rachis is extremely brittle: b) the lateral branches are not suppressed, but grow perfectly normally, producing terminally a tassel or an ear, and laterally still more branches or higher order with a varying number of additional ears: c) instead of a reduced or sterile ear, we encounter ears, where one female spikelet tends to be associated with a male spikelet.

While I think that the general structure of the Pod-Corn-Teosinte hybrid is a more likely reproduction of a hypothetic wild ancestor of corn as compared with the bearded Pod Corn, I do not believe that this ancestor actually was a hybrid.

There have been proposed several hypotheses to explain the morphological nature of the many ranked corn ear. Here again our Pod-Corn-Teosinte hybrids offer valuable material since the paired spikelets are often different, one being sessile and the other pedicelled. In two-ranked ears or in tassel branches we find in general a very regular situation. Both sessile spikelets are localized near the ventral side of each alveolus and the pedicelled spikelets on the dorsal side. But this symmetry seems to be the consequence of some physiological conditions. In many-ranked ears I did not find a regular position of two spikelets of the alveoli of each double row. The sessile spikelet may be on the left or on the right side of the pedicelled spikelet.

Other interesting observations could be made in some of the F2 plants. In several instances, an alveolus contained one sessile spikelet and one "branch" which carried one spikelet more or less in the middle and another at the end. If the pedicel was shortened three spikelets appeared close together in the alveolus. In one instance an alveolus contained 4 spikelets which probably were derived from two reduced branches with 2 spikelets each.

Finally all observations seem to indicate that the only constant orientation of the alveolus may be the longitudinal row, sometimes obscured by a twisting of the rachis, or altered by the intercalation of new double rows. The appearance of 3 rows of alveoli, the transition of this arrangement into one with either 2, by suppression, or of 4 double rows, by intercalation, is quite frequent. The alveoli may be all at different levels, or at the same level. Neither yoking nor a spiral arrangement could be observed with any regularity.

Thus the Tu F1 and F2 plants offer very interesting material, especially when studied at flowering time and not when their ears have become hard and mature. There cannot be any doubt that this material will finally permit a critical discussion of the hypothesis of the nature of the ear and the formulation of a new, combined theory, containing to some extent elements of older views. But the final discussion will be delayed until the analysis of the mature F2 and backcross ears is completed.

F. G. Brieger

Monaco'>The Tu effect on the tassel was completely recessive‑hypostatic and it was impossible to classify the F1 plants as in the original "So Paulo Pod" according to the transformation of the tassel. Thus the tassels of Tu plants and their normal tu sisters were identical.

 

The ears, however, were very different in Tu and tu hybrids. In the rows were mainly single, or when the paired row was not suppressed, they contained female spikelets only. Two paired rows appeared generally in the Tu plants, one being an ordinary female spikelet, with one sterile and one female flower, while the other spikelet became pedicelled and contained two male flowers. Furthermore, there was a pronounced tendency to produce not only 2 double rows, but 3 or even 4.

 

The scales formed by the rachis and which cover more or less the grains in teosinte or in tu F1 plants, were smaller and soft in Tu plants while the glumes became pointed.

 

The rachis and glumes of the tu hybrids are extremely horny, and it was very hard work to shell the seeds. On the other side, the rachis in Tu F1 plants is extremely brittle and it was nearly impossible to harvest complete mature ears, since they fell apart immediately after removing the shucks.

 

Thus the Tu gene has a very different phenotypic effect in pure corn and in teosinte‑corn hybrids. In the former we observe a pronounced tendency to introduce femaleness into the tassel, while in the latter maleness appears in the ears, or better on the lateral branches. A selection experiment is under way with the end of fixing this condition, just as it was possible to fix more or less the bearded tassel.

 

The fact that the Tu‑gene acts in nearly opposite directions according to the modifier complex present, should warn us not to draw premature conclusions on gene action. The appearance of covered kernels is a universal effect of the Tu gene, while everything else depends upon the modifier back‑ground. The Tu F1 plants described above seem to me much more likely to be a replica of an ancestral wild grass than the Tu corn plants with beardgd tassel, especially considering the following points: a) the rachis is extremely brittle: b) the lateral branches are not suppressed, but grow perfectly normally, producing terminally a tassel or an ear, and laterally still more branches or higher order with a varying number of additional ears: c) instead of a reduced or sterile ear, we encounter ears, where one female spikelet tends to be associated with a male spikelet.

 

While I think that the general structure of the Pod‑Corn‑Teosinte hybrid is a more likely reproduction of a hypothetic wild ancestor of corn as compared with the bearded Pod Corn, I do not believe that this ancestor actually was a hybrid.

 

There have been proposed several hypotheses to explain the morphological nature of the many ranked corn ear. Here again our Pod‑Corn-Teosinte hybrids offer valuable material since the paired spikelets are often different, one being sessile and the other pedicelled. In two‑ranked ears or in tassel branches we find in general a very regular situation. Both sessile spikelets are localized near the ventral side of each alveolus and the pedicelled spikelets on the dorsal side. But this symmetry seems to be the consequence of some physiological conditions. In many‑ranked ears I did not find a regular position of two spikelets of the alveoli of each double row. The sessile spikelet may be on the left or on the right side of the pedicelled spikelet.

 

Other interesting observations could be made in some of the F2 plants. In several instances, an alveolus contained one sessile spikelet and one "branch" which carried one spikelet more or less in the middle and another at the end. If the  pedicel was shortened three spikelets appeared close together in the alveolus. In one instance an alveolus contained 4 spikelets which probably were derived from two reduced branches with 2 spikelets each.

 

Finally all observations seem to indicate that the only constant orientation of the alveolus may be the longitudinal row, sometimes obscured by a twisting of the rachis, or altered by the intercalation of new double rows. The appearance of 3 rows of alveoli, the transition of this arrange­ment into one with either 2, by suppression, or of 4 double rows, by intercalation, is quite frequent. The alveoli may be all at different levels, or at the same level. Neither yoking nor a spiral arrangement could be observed with any regularity.

 

Thus the Tu F1 and F2 plants offer very interesting material, especially when studied at flowering time and not when their ears have become hard and mature. There cannot be any doubt that this material will finally permit a critical discussion of the hypothesis of the nature of the ear and the formulation of a new, combined theory, containing to some extent elements of older views. But the final discussion will be delayed until the analysis of the mature F2 and backcross ears is completed.

 

F. G. Brieger