The Relation between Light Variegated and Medium Variegated Pericarp in Maize.

HE present report is based upon a restudy of variegated pericarp in Tmaize, a mutable character which is well known through the important pioneer work of EMERSON (1914, 1917, 1929). The current investigation is concerned primarily with the relation between two distinct phenotypes, light variegated and medium variegated, both of which are unstable, The results obtained, however, bear directly on the allied problem of the kind of change which occurs when variegated is transformed to the stable self colored type. Two facts emerging from EMERSON'S experiments should be noted here. EMERSON (1917) found that in families obtained by selfing variegated plants heterozygous for the stable red cobbed white allele ( W R ) ,3 variegated ( V V ) mutates somatically to self colored ( R R ) more than twice as frequently in heterozygotes ( V V / W R ) , in which it is present once, as in homozygotes (VV/ V V ) which are duplex for the mutable gene. This observation, which will not be discussed further at present, has been amply confirmed in our work. The second fact was rather startling since, as EMERSON (1929) recognized, it might have been interpreted as evidence of gene contamination. The capacity of a W R allele of given origin seemingly to " stimulate " the mutation of variegated to self red in V V / W R heterozygotes was found to be reduced if, in the preceding generation, the gene passed through a V V / W R plant which showed a low grade of variegation. In a gross statistical sense, this relation also is confirmed in our experiments. EMERSON (1929) considered it unlikely, however, that the W R allele itself was the element affecting the V V / W R heterozygote. H e assumed, on the other hand, that the mutation modifier present in W R stocks was a gene (or genes) closely linked to, but distinct from, the P locus and subject to crossing over with alternative forms of the modifier occurring in the variegated races tested. Definitive evidence for the postulated second locus was not brought forward. The additional facts now at hand make it improbable that a satis-