Abstract
The low temperature requirements for flower bud differentiation of Brussels sprouts were investigated. Five cultivars of plants were treated at 6 or 10 weeks old with a low temperature of 4℃ for 4 or 6 weeks. The plants were grown in a 16 hr day-length under fluorescent lights (PPFD 35 μmol・m^<-2>・s^<-1>) during the treatment. Budding of 'Family Seven' plants occurred when they were treated at 6 weeks old for 6 weeks, and at 10 weeks old for 4 weeks. Budding of 'Cluster', 'Early Green', and 'Wase Komochi' plants did not occur when they were treated at 6 weeks old, but did occur when they were treated at 10 weeks old for 4 weeks. Budding of 'Kodakara' plants occurred only when they were treated at 10 weeks old for 6 weeks. Flower buds of 'Family Seven' plants treated at 6 weeks old were differentiated at lower nodes and earlier than plants treated at 10 weeks old. When 'Family Seven', 'Cluster', 'Early Green', and 'Wase Komochi' plants were treated at 10 weeks old for 4 or 6 weeks, no difference was found in the number of nodes bearing first flower buds. From these results it was shown that Brussels sprouts have a low temperature requirement of plant vernalization for flower bud differentiation, and there were cultivar differences in low temperature requirement for flower bud differentiation.
