Paramutation and mutation of R (ch) in maize.

1. In maize, R (ch) conditions anthocyanin pigmentation in aleurone, anthers, silks and reacts with another factor Pl to produce cherrycoloured pericarp, thus representing the broadest pigmentation pattern among all the alleles at the R locus. The paramutational and mutational behaviour of R (ch) are reported here. 2. R (ch) is paramutable with respect to its action in the aleurone, but its pigmenting ability in the pericarp is not sensitive to the paramutagenic action of R (st) . 3. The mutation experiments revealed that R (ch) is a compound locus containing at least four different components: (P) affecting anthocyanin in anthers, (Si) conditioning pink silks, (Ch) reacting with Pl to produce cherry pericarp, and (S) affecting aleurone pigmentation. 4. Different interactions of R (ch) with independent genes support the conclusions drawn from mutation experiments. 5. It is suggested that different components of the R (ch) locus are unequally sensitive to the action of R (st) .