A pink aleurone color, varying in intensity and giving a mottled appearance, was observed in stocks of corn homozygous a1a1 and heterozygous Dtdt. Crosses made in the summer of 1946, in the course of other studies with this stock, indicated an unusual mode of inheritance of this color factor called flush.
In general, of 105 ears examined, all were either 100% flush, 100% colorless, or segregating 1:1. Selfed plants from flush kernels of segregating ears had two classes of ears; some were altogether colored, and others segregated 1:1. Selfed plants fron colorless kernels of these same segregating ears also had two classes of ears; some colorless and some segregating 1:1.
Further crosses made in the summer of 1947 indicated the same pattern of inheritance and especially the total lack of effect of the male parent in determining the phenotype of the offspring.
When the female parent is homozygous for flush, all offspring kernels will be colored regardless of the male constitution, provided only that it comes from the same stock. When the female parent is homozygous colorless, all offspring kernels are colorless. When the female parent is heterozygous, all ears segregate 1:1. However, let us consider the genotype of these kernels. When a heterozygous plant is selfed, half the colored kernels of the offspring ear will be homozygous flush and half heterozygous. Half the colorless kernels will also be heterozygous for flush and half homozygous colorless. All these cases have been observed.
The data indicate that the expression of flush depends upon the presence of the allele for color in at least two of the three loci present in each aleurone cell. There is no dominance. This mode of inheritance resembles that of floury.
Linkage tests are in progress. Expression of flush is independent of Dt. It follows then that the aleurone color factors A2 C and R are all homozygous dominant. When homozygous flush plants were used as female times a1‑et tester stock, the offspring ears were all colorless, indicating the male carried some factor inhibiting expression of flush. However, when sib females were crossed to C.497 a1 tester, some of the kernels on the offspring ear were pigmented faintly.
The variability in intensity of color seems to be affected greatly by both environmental conditions and modifiers. Careful grading of color intensity of several ears individually gave in each case a fairly typical normal distribration range with no appearance of sharp discontinuities or classes. When a pale flush heterozygote female was crossed to a deep flush male, the colored kernels on the offspring ear were, on the average, deeper in color than were the colored kernels on ears from crosses of sib females to pale flush males. Thus it appears that the male parent carries modifiers that can affect the intensity of pigmentation, but the male cannot determine whether or not the color will be present.
Under controlled environmental conditions this factor may be useful for a quantitative study of modifiers, and further work is in progress.