Somatic Reduction of Tetraploid Sorghum to Diploid Mutants following Colchicine Treatment

Abstract

COLCHICINE treatment of seedlings of certain sorghum lines has resulted not only in the expected polyploids, but also in diploid plants which are mutant for many characters. Some of these diploid mutants breed true immediately while others give segregating progenies1–3. The original hypothesis to explain their appearance suggested that a somatic reduction of the chromosomes (similar to that observed by Huskins4) occurred and was followed by duplication. These mechanisms could result in the concentration of chromatin from ancestors of a putative allopolyploid. However, investigations have produced either no or little cytological evidence for duplication or relocation of chromatin5,6. In addition, mutant characters which have been studied have shown Mendelian inheritance7–10. The alternative hypothesis was then proposed that, in addition to a balanced somatic reduction of the chromosomes after application of colchicine, mutations at many loci also occurred prior to duplication back to the diploid number.