White asparagus production with opaque film in rootstock planting forcing culture

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 one-year-old rootstocks of cultivars with a low level of dormancy ('UC-157 Fsub(1)' 'GrandeFsub(1)') if spears are harvested under dark conditions maintained by opaque film covering.