Induced Premeiotic Exchange of Linked Markers in the Angiosperm Arabidopsis

is well known that X rays produce various types of chromosomal reCrrangements and deficiencies which may cause variegation, but induced reassortment of markers on homologous chromatids appears not to have been reported. In higher plants, somatic variegation can rarely be subjected to critical analysis. One major difficulty is the limited number of appropriate somatic markers usable to distinguish the mechanisms causing variegation. Another is that, although it may be possible, by dedifferentiating and redifferentiating somatic cells, to obtain progenies from the critical segments (cf. STEWARD, MAPES. KENT and HOLSTEN 1964) , this is not yet simple and practical for classical genetic analyses. The felicitous material used in this study reduced these barriers, and permitted several somatic sectors of interest to be subjected to genetic analysis (progeny test). Investigations on this problem would not have been initiated in Arabidopsis thaliana, a typical higher plant, had not twin spots appeared in some experiments designed primarily to induce and detect locus-specific mutations and deletions ( RBDEI 1960, unpublished; HIRONO and RBDEI 1963b). This report demonstrates induced premeiotic exchange of linked markers in an angiosperm, simulating crossing over. The analysis to follow indicates, however, a different mechanism, possibly a translocation between homologous chromatids.