Selection of useful purple sprouting broccoli (Brassica oleracea L. Italica Group) cultivars for cultivation in Japan

Purple sprouting broccoli (“PSB”) is a vegetable cultivated for commercial purposes primarily in Britain along the west coast with its marine climate, and the lateral branches are harvested. The results of a preliminary examination suggested the problem of it taking too long for the buds of the “PSB” cultivated in Japan, a country with a warm and wet climate, to sprout. Therefore, in order to introduce “PSB” to Japan, it is necessary to select and cultivate appropriate cultivars while taking the yields and characteristics of the bearing of buds into consideration. A survey was conducted to examine the yields of ‘Santee’, an early maturing cultivar, cultivated in fields of Japan, and the number of days for the plants to bear buds over two cropping seasons between 2014 and 2016. The yields of ‘Santee’ planted in August to September were equal to or higher than those of ‘Pixel’ (broccoli) and ‘Stick Señor’ (sprouting broccoli). However, the start of the harvest of ‘Santee’ planted in August to September was later than that of ‘Pixel’ and ‘Stick Señor’ planted around the same period. To examine the budding characteristics of “PSB” cultivars that can be harvested earlier than ‘Santee’, the morphological characteristics of nine “PSB” cultivars and the number of days for them to bear buds were compared. The number of days required for ‘Rioja’ to bear buds was significantly shorter than the period required for other cultivars. Regarding the morphological characteristics, the diameter of the stem of ‘Mendocino’ was significantly greater and its yield was higher compared with other cultivars. When considered from the viewpoint of characteristics, ‘Rioja’, which requires only a short period of time to bear buds, and fertile ‘Mendocino’, with its thick stems, are favorable PSB” cultivars to be cultivated in the warm and wet climate of Japan.