PERSISTENT ENHANCEMENT OF Rr ACTION IN MAIZE BY STRUCTURAL ALTERATIONS OF CHROMOSOME 10

HE anthocyanin-producing action of the R' allele in maize invariably is reduced by passing R' through a heterozygote with the stippled ( RrRSt) or the marbled allele ( RrRmb). The induced changes in R' are gametically transmissible in metastable form (BRINK 1956, 1960; BRINK and WEYERS 1957; BRINK and MIKULA 1958). It is now found that Rr activity can regularly be altered in directed fashion also, in a quite different way, namely, by insertion of the factor in certain reciprocal translocations involving the long arm of chromosome 10 in which the R locus is situated. The change in Rr action in these cases is to a higher-than-standard level of pigment production; and the increase persists in the absence of the inciting agent. The results of experiments with two such structural alterations are presented in the present article.