2. Maize-teosinte crosses. Studies of the genetics of maize-teosinte crosses have been greatly facilitated by the development of a stock with a marker gene on each of nine chromosomes, ten if the other parent is pr. (bm2 lg a su Pr Y/y gl j wx g) This stock has been inbred and is uniform. Needless to say it is weak, so weak that most of the plants are barren and many do not shed pollen. But difficult as it is to maintain the stock is extremely valuable. It imparts considerable vigor to its crosses and it permits the investigator to control nine of the ten chromosomes in a single cross.
This stock was crossed with two varieties of teosinte, Durango and Nobogame. F2 results are shown in the accompanying table. In the Nobogame cross the nine marked chromosomes segregate independently of each other as would be expected if no translocations, "sticky" chromosomes or other complicating factors are involved. In the Durango cross there are two significant deviations, one in the direction of linkage between Su and J and another indicating "repulsion" between Wx and Gl. There are additional deviations approaching statistical significance in the Durango cross.
In addition to the nine marker genes tho plants in both crosses were scored for five characteristics, in which maize and teosinte differ. One of these, a red spot at the base of the staminate glumes, Bs, is also found in some maize varieties, particularly South American and is not regarded as an important character from the standpoint of differentiating maize and teosinte. The remaining four are characters involved in interspecific differences. They are (with the teosinte characters listed first):
1. Tr Two-ranked vs. many-ranked ear or central spike.
2. Pd Single vs. paired spikelets.
3. Sd Strong vs. weak response to length of day.
4. G. S. (Glume Score) Prominent horny glumes vs. inconspicuous membranous glumes.
Langham's symbols for tho first three characteristics are used although the characters involved did not prove to be simple monofactorial in their inheritance in these crosses. All of these characters showed linkage with each other and all but the second showed linkage with one or more of the nine marker genes.