Genetic Similarity of Colchicine-induced Grass-type Mutants in Sorghum

The induction of true-breeding diploid mutants in certain varieties of Sorghum Vulgare Pers. by application of 0.5 per cent colchicine in lanolin to the coleoptile of the seedlings has been previously reported. Both cytological and genetical evidences obtained by various investigators have indicated the occurrence of gene mutations previous to or concurrent with the reduction division. The repeated occurrence of mutants with identical phenotypes involving whole complexes of characters raises the problem of whether identical major chromatin rearrangements or identical mutagenic effects are responsible. This study was designed to determine whether the phenotypically similar mutants are also genotypically similar. Genetical and cytological observations were made on three phenotypically similar grass mutants which arose from the sorghum variety Experimental 3 after colchicine treatment in different years. For this study, three phenotypically similar grass-type mutants derived from one variety after colchicine treatments by C. J. Franzke in 1948 and 1955, and by M. E. Sanders and C. J. Franzke in 1957, respectively, and the original variety, Experimental 3, were involved in this study. The modes of inheritance of cour different contrasting characters, namely, red vs. green seedling base, dry vs. juicy midrib, purple vs. non-purple spotting on leaf blade, and awnless vs. awned, were analyzed from the results obtained from five categories of crosses