Breeding of Bolting Resistance in Chinese Cabbage. Critical Day Length for Flower Induction of Late Bolting Material with No Chilling Requirement.

The critical day length to induce bolting and flowering in the late bolting cultivar 'Osaka Shirona Bansei' of Brassica campestris L. (syn.B. rapa L.) ssp.pekinensis was examined.'Osaka Shirona Bansei', a non-heading leaf vegetable, was almost insensitive to the chilling treatment but sensitive to the long day length for the bolting and flowering.Regardless of chilling treatment, the critical day length was around 14 hr.The possibility of introducing this unique bolting character into the heading Chinese cabbage type is discussed.