Segregation frequencies of radiation-induced viable mutants in Arabidopsis thaliana (L.) Heynh.

The segregation of viable mutants derived from various fast neutron and X-ray treatments of Arabidopsis seeds was studied in the M2- and M3-generation. An equal segregation frequency in the M2- and M3-generation was observed. This indicated that the M2-lines, each of which descended from a single silique from the top of the main inflorescence of an M1-plant, originated from non-chimeric tissue. Furthermore, it was found that neither radiation type nor radiation dose affected the segregation frequency of the mutants. The average segregation frequency of the mutants was 21.5 per cent and significantly below the Mendelian expectation of 25 per cent. It was found that the mutant deficit was mainly due to reduced transmission of the mutant gene through the gametophyte. These findings are discussed with reference to the transformation of mutant frequency scores to mutation frequency per cell.