AN UNSTABLE MUTATION FOR PIGMENTATION IN KERNELS OF CALICO SORGHUM

Most plants of 'Calico' sorghum [Sorghum bicolor (L.)] are chimeric for pericarp pigmentation and characterized by variegated kernel color. Data showed that 'Calico' sorghum plants carry two unstable alleles at the Y locus. Inheritance patterns of pericarp pigmentation or kernel color did not fit Mendelian rules and were very similar to P locus mutation of maize. This study suggested the involvement of a transposable genetic element (TGE). Insertion of a TGE or "mutation" in the Y locus, one of the two loci controlling pericarp pigmentation, would lead to the loss of red pigment synthesis and the appearance of white pericarp. Reversion of the mutated alleles or excision of the TGE from the Y locus would produce either red striped or entirely red kernels on the panicle. The number and size of the stripes on the kernel appeared to depend on the frequency and developmental stage of the reversions.