CYTOLOGICAL STUDIES OF NONTRUE–BREEDING MUTANTS IN SORGHUM OBTAINED AFTER COLCHICINE TREATMENT

Sanders , Mary E., and Clifford J. Franzke . (South Dakota State Coll.. Brookings.) Cytological studies of nontrue-breeding mutants in sorghum obtained after colchicine treatment. Amer. Jour. Bot. 49(9): 990–996. Illus. 1962.—Although pollen mother cells of nontrue-breeding mutant plants obtained after colchicine treatment of sorghum seedlings, line ‘Experimental 3,’ showed normal chromosome behavior (10 bivalents) at phases of meiosis I, some abnormalities were found at corresponding stages in first- and second-generation self-progeny plants of some of them. The most frequent chromosome irregularities were an increase over ‘Experimental 3’ in number of cells containing univalents, and mixoploid tissues with tetraploid and diploid cells. The higher polyploid groups (6n, 8n, 10n) also present in 2 plants might be related to their male-sterile condition rather than being an indication of the chromosome complement. Abnormalities in progenies suggest that some of the mutants might have been chimeras in which abnormalities were missed and raise the question whether chromosome changes are involved in the formation of the mutants in spite of the preponderance of normal diploid cells with 10 bivalents during prophase and metaphase of meiosis I. This could occur if sorghum contains a genetic mechanism which promotes bivalent rather than multivalent pairing. That such might be a possibility is indicated by the large numbers of bivalents and small numbers of multivalents found in polyploid cells or groups.