GENETIC INTERACTIONS AMONG LATE-FLOWERING MUTANTS OF ARABIDOPSIS

Flowering time in Arabidopsis is controlled by a large number of genes , identified by induced mutations. Forty-two double mutants involving 10 of these loci were obtained and analyzed for their flowering behavi or under long-day conditions, with and without vernalization, and unde r short-day conditions. The genetic interactions between the various m utants proved to be complex, although a major epistatic group (called group A) could be identified corresponding to the mutants, which are r elatively insensitive to vernalization and daylength. In contrast, the genetic behavior of the mutants much more responsive to these environ mental factors (group B) is more complex. The vernalization responsive ness of the group B mutants did not compensate for the lateness of the group A mutants. This indicated that these genes do not control verna lization sensitivity as such, but provide a factor that becomes limiti ng in short days. The classification of these mutants in different phy siological groups is discussed in relation to the detected genetic int eractions, and based on these interactions a more detailed model of th eir role in flowering initiation is proposed.