4. The Anthocyanin Pigments of Corn. According to Sando et al, the plant pigment of purple corn (A B Pl Rr) is chrysanthemin. The anthocyanin pigments present in other types have not previously been reported.
The anthocyanins which occur most commonly as flower color, pigments (glycosides of pelargonidin, cyanidin, delphinidin, peonidin, malvidin and petunidin) may be identified by simple qualitative tests outlined by Robinson and Robinson. The reactions of many less commonly occurring anthocyanins and of some synthetic anthocyanins not known to occur naturally have been summarized by Karrer.
Robinson's qualitative tests have been applied to the pigments extracted from numerous genetic types of corn. Although some of the pigments were identifiable with the qualitative tests, there were several which proved to be distinctly different in their reactions from the common flower pigments listed above.
An F2 of the hybrid a pr b pl Rg × A Pr B Pl Rr was closely examined for color variations. In addition to the familiar plant color types expected from this cross, there were various minor modifications which have not previously been analyzed genetically. Plant material was taken from many of these plants for analysis, and all of the plants were self-fertilized.
The "A" type plants (A B Pl) in this hybrid population fall into three fairly distinct groups: (1) deep bluish purple, (2) deep reddish purple (maroon) and (3) light, distinctly reddish purple (dilute). The anthocyanins extracted from these plants included typical pelargonidin as well as typical chrysanthemin, and also in several cases pigments giving a typical reaction. The pigment differences are not always evident from the external appearance of the plant. Both chrysanthemin and pelargonidin are found among the deep bluish purple plants and among the maroon plants, but chrysanthemin is not found in the "dilute" class.
In F3, pure breeding families of the above described types were established. One deep bluish-purple family contained typical chrysanthemin. One deep bluish purple, indistinguishable from the chrysanthemin family except by anther color, contained a pigment which differed only slightly in reactions from pelargonidin 3-monoside, and one family of reddish purple (maroon) had pigment apparently identical to that of the deep purple pelargonidin type. A pure breeding "dilute" family showed typical pelargonidin 3-monoside reactions.
The pigment of "B" type plants (A B pl) showed reactions not typical of any of the commonly occurring anthocyanin types, Although there was variation in intensity of pigmentation comparable to that among the "A" type plants, no differences in the pigment of the different "B" type plants have been established.
The variation in intensity of the "E" type (aBPl) plants is correlated, at least to a large extent, with that of "A" type plants. In families with "A" type plants mostly deep purple, the "E" types were mostly deep brown and in families of "dilute" pigmentation it was difficult to distinguish a B Pl from a B Pl plants until the plants were nearly mature.
The pure breeding pelargonidin families of this stock were recessive pr but in many plants of this hybrid the Pr separation was doubtful. Therefore tests were made on different hybrids with positive Pr separation to establish this relation. In the first planting, the Pr plants, (6 in number) all contained chrysanthemin and the pr plants (8 in number) pelargonidin 3-monoside. In tests on the Pr and pr plants from six ears of the progeny of this family (self-fertilized or back-crossed) the same results were obtained. The pigment was found to be the same in all parts of the plant, including roots, coleoptile, sheath, husks, cob and aleurone.
Analyses have been made of pigments characteristic of other A alleles, in plants with B and Pl. Ab gives chrysanthemin indistinguishable from that of A-plants of the same culture. Standard ap, several mutant ap's (by spontaneous mutation from Ab), and Alt, (an ultraviolet mutant of A), all give mixtures oF anthocyanin and flavonol in varying proportions. The anthocyanin in these mixtures, however, is distinct from that produced by A and Ab and resembles in some reactions the pigments of sun-red plants.
J. E. McClary