THE PHENOTYPE OF SOME LATE-FLOWERING MUTANTS IS ENHANCED BY A LOCUS ON CHROMOSOME-5 THAT IS NOT EFFECTIVE IN THE LANDSBERG ERECTA WILD-TYPE

Late-flowering mutants that have been described in ecotypes other than Landsberg erecta (Ler) have been found to be dominant alleles of the FRI locus located on chromosome 4, which determines lateness in many v ery late ecotypes. The extreme lateness of dominant FRI alleles depend s on dominant alleles at the FLC locus that maps on the top of chromos ome 5. FLC alleles with this effect have been found in all ecotypes te sted (Col, Ws, S96, Est and Li) except Ler. Most likely the same locus confers lateness to the luminidependens (Id) mutant. Genotypes with a dominant FRI allele and the monogenic recessive id mutant are only sl ightly later with recessive Ler alleles at the FLC locus. Genotypes wh ere the dominant FLC alleles are combined with FRI or with the Id muta nt, are strongly responsive to vernalization, which is much less effec tive in the FLC-Ler background.