Work of the United States Department of Agriculture on Plant Hybridisation (1900)
Herbert J. Webber
(In charge of the Plant-Breeding Laboratory)

CORN OR MAIZE HYBRIDISATION

Only very few of the numerous important problems here presented to the plant breeder have as yet been taken up. In the hope of securing better-yielding races the exceedingly large-kernelled Cuzco, or Peruvian Corn recently imported into the United States by the Department of Agriculture, was used in hybridising with certain of our best races. The Hickory King, a very large-kernelled white dent, and Leaming, a well-known yellow dent, were used as the seed-bearing parents. The Cuzco, from which the pollen for the hybrids was obtained, was grown from kernels of a graphite colour, this colour being distinct from that of any race of Corn in the United States with which I am familiar.

*The crosses of Leaming with Cuzco were made by Mr. E. C. Rittue, gardener of the Division of Vegetable Physiology and Pathology, at my request.

The current or immediate effect of pollen (xenia), so commonly reported as occurring in Corn, was shown in these hybrids; and although no check experiments were made (the work not being carried on to demonstrate this feature), there can nevertheless be no doubt that the coloration was due to the effect of the pollen. The seed of the Hickory King and the Leaming used was grown by careful seedsmen, and strict attention was given to keeping it pure and true to type. None of the ears except those which had been crossed showed any indication of impurity. Some of the kernels of the Hickory King ears crossed with the pollen of the Cuzco showed irregular spots of the characteristic graphite colour of the Cuzco, while others were entirely of a slate colour, these being somewhat lighter in colour than those of the typical Cuzco. So far as could be observed, the Cuzco used was not a fixed type, some of the kernels being mottled with red, olive purple, or brown. In a few instances the immediate effect of the pollen was apparent in Leaming crossed with Cuzco,* the kernels showing a peculiar admixture of the colours of the parents, that is of dark olive purple and the orange yellow. In the case of the hybrids of Hickory King with Cuzco grown from kernels showing the immediate effect of the pollen, which were marked when planted, their increased vigour, purple stalks, and whorls of anchor roots (inherited from the Cuzco, the male parent) showed that they were without question hybrids of the two races named. In the same characteristic way the influence of the male parent was evident in many of the hybrids from kernels in which no immediate effect of the pollen was shown. All hybrids showing intermediate characters were very late in flowering, which is another characteristic of the Cuzco, it being a tropical plant, and therefore requiring a long season to develop. These hybrids as a rule matured slightly earlier than the Cuzco plants in the same field.

Other hybrids have been made with a view of securing sorts that will yield better in northern regions, where flint Corn, which ripens early but is a poor yielder, is now grown. Some of these hybrids are very promising; for instance, one of Gilman Flint (a good race of the flint Corn) when crossed with Leaming pollen produced ears almost twice as large as those produced by the Gilman Flint grown under similar conditions, there being sixteen rows of kernels on the ear instead of twelve, as in the Gilman Flint, and the kernels being much larger. This hybrid ripened nearly as early as the Gilman Flint, being secure from injury by frost three months after it was planted.

It is the intention of the Department to test such hybrids in the regions to which they seem best adapted, and to fix races of such as are found valuable.