To facilitate the production of white asparagus (Asparagus officinalis L.) spears in winter, we studied spear blanching in rootstock planting forcing culture. A strong correlation was observed between the fresh weight of one-year-old rootstocks and their yields. Light conditions during the harvesting time had little influence on the yield, but, they influenced anthocyanin pigmentation in the spear. When asparagus spears were harvested under darkness maintained by an opaque film covering, anthocyanin pigments in the spears disappeared. There were differences between cultivar yields; these were caused by the differences in the extent of chilling exposure, which is necessary for each cultivar to break the dormancy of its rootstock. These results suggested that white asparagus spears can be produced with no anthocyanin pigment in forcing culture by using oneyear-old rootstocks of cultivars with a low level of dormancy ('UC-157 F 1 ', 'GrandeF 1 '), if spears are harvested under dark conditions maintained by opaque film covering.Key Words：anthocyanin, dormancy, light condition, opaque film covering

Sweetpotato has recently received much attention due to its many agricultural advantages such as its adaptability to different environmental conditions and its nutritional value. It has been grown in Japan for more than 400 years, and the bulk of the Japanese harvest is presently destined for fresh market consumption as well as for the food and beverage processing industry. This review begins by providing an overview of the commercial production and agronomic characteristics of sweetpotato cultivars in Japan. The paper deals with the possible ancestry of Japanese sweetpotatoes, and finally describes several orange- or purple-fleshed genotypes that are adapted well to cold northern climates and considered as valuable sources for enhancing the physiological functionality of this crop.

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