Germinal derivatives of the En controlling-element system in maize: Characterization of colored, pale and colorless derivatives a2-m.

Several stable germinal derivatives, with varied phenotypic expression have been recovered from testcrosses of four different a2 mutable alleles (a2m-7 8018, a2m-6 8144, a2m-6 8140, and a2m-1 1511) under the control of the En controlling-element system. These are colored, pale, and colorless aleurone types; the former two represent mutations of a2-m→A2' type. The phenotypic variation among colored and pale derivatives has been confirmed by quantitative determination of anthocyanin content in the aleurone tissue of the kernels.The data suggest that significant variation exists between phenotypically similar colored derivatives arising from different mutable alleles as well as from the same source allele. Every tested colored derivative is significantly different from the pale, colorless, and colored control (W22 color converted line). Genetic analysis of these colored derivatives suggests that all of them contain one or more En and, hence, they are characterized as permanent changes of a nonresponsive (nr) type. Their frequencies are variable among the testcrosses.Similarly, the pale derivatives, which are clearly different from colored and colorless, also show significant differences in terms of anthocyanin content. Significant differences exist between pales arising from the same allele as well as between pales arising from different alleles. All the tested pales are significantly different from colorless and colored derivatives. Thus, the pales, as well as colored derivatives, represent a differential impairment of anthocyanin synthesis in the aleurone tissue. The genetic analysis confirmed that all the pales, except the pales of a2m-1 1511, lack the capacity to respond to En. These pale derivatives can be with or without En.Qualitative differences among the colored, pale, and colorless types have been investigated by thin-layer chromatographic and spectroscopic techniques. The results suggest that there are no qualitative differences, in terms of anthocyanin pigments, between colored, pale, and colored control. All accumulate the same anthocyanins (namely, cyanidin-3-glucoside and pelargonidin-3-glucoside in appropriate proportions depending upon the Pr and pr constitution).