MAPPING LOCI CONTROLLING FLOWERING TIME IN BRASSICA-OLERACEA

The timing of the transition from vegetative to reproductive phase is a major determinant of the morphology and value of Brassica oleracea c rops. Quantitative trait loci (QTLs) controlling flowering time in B. oleracea were mapped using restriction fragment length polymorphism (R FLP) loci and flowering data of F-3 families derived from a cabbage by broccoli cross. Plants were grown in the field, and a total of 15 sur veys were made throughout the experiment at 5-15 day intervals, in whi ch plants were inspected for the presence of flower buds or open flowe rs. The flowering traits used for data analysis were the proportion of annual plants (PF) within each F-3 family at the end of the experimen t, and a flowering-time index (FT) that combined both qualitative (ann ual/biennial) and quantitative (days to flowering) information. Two QT Ls on different linkage groups were found associated with both PF and FT and one additional QTL was found associated only with FT. When comb ined in a multi-locus model, all three QTLs explained 54.1% of the phe notypic variation in FT. Epistasis was found between two genomic regio ns associated with FT. Comparisons of map positions of QTLs in B. oler acea with those in B. napus and B. rapa provided no evidence for conse rvation of genomic regions associated with flowering time between thes e species.