COMPARISON OF FLOWERING TIME GENES IN BRASSICA-RAPA, BRASSICA-NAPUS AND ARABIDOPSIS-THALIANA

The major difference between annual and biennial cultivars of oilseed Brassica napus and B. rapa is conferred by genes controlling vernaliza tion-responsive flowering time. These genes were compared between the species by aligning the map positions of flowering time quantitative t rait loci (QTLs) detected in a segregating population of each species. The results suggest that two major QTLs identified in B. mpa correspo nd to two major QTLs identified in B. napus. Since B, rapa is one of t he hypothesized diploid parents of the amphidiploid B. napus, the vern alization requirement of B. napus probably originated from B. rapa. Br assica genes also were compared to flowering time genes in Arabidopsis thaliana by mapping RFLP loci with the same probes in both B. napus a nd Arabidopsis. The region containing one pair of Brassica QTLs was co llinear with the top of chromosome 5 in A. thaliana where flowering ti me genes FLC, FY and CO are located. The region containing the second pair of QTLs showed fractured collinearity with Several regions of the Arabidopsis genome, including the top of chromosome 4 where FRI is lo cated. Thus, these Brassica genes may correspond to two genes (FLC and FRI) that regulate flowering time in the latest flowering ecotypes of Arabidopsis.