Relative insensitivity of enhanced Rr to paramutation in maize plants heterozygous for the stippled allele.

ATA presented in the preceding article (BRINK and BLACKWOOD 1961) D demonstrate that the effect of R' on aleurone color in maize is enhanced when the factor is carried by, or passed through, either of two reciprocal translocations, T2-10a and T4-lob, involving breaks in the long arm of chromosome 10 proximal to, but well removed from, the R locus. The change in phenotype is from darkly mottled in R'rgrg testcross kernels to near-self-color in T2-1 Oa R'/rgrg and T4-10b R'/rgrg seeds. There is a lag of at least one generation in the manifestation of such enhancement after introducing R' from a stock source into a structurally altered chromosome; and the change, once induced, persists for at least one generation following return of the allele to a structurally normal chromosome 10, by crossing over. The results summarized in the present report establish the additional fact that R', on thus being changed from the standard to the enhanced form, is much less sensitive than a normal R' allele to reduction in aleurone pigment-producing potential in plants heterozygous for the stippled (R") allele.