New all-male asparagus hybrid 'Zuiyu'.

cool regions in Japan. This cultivar was released by Hokkaido National Agricultural Experiment Station (present name: National Agricultural Research Center for Hokkaido Region) and registered as Norin hybrid No.1' of asparagus with Japan's Ministry of Agriculture, Forestry and Fisheries (MAFF) in 1999. 'Zuiyu' is an F1 hybrid resulting from a cross of the clonal seed parent 'Zuiyo-2' and the pollen parent 'ZM-19'. 'Zuiyu' yield is higher than that of the standard cultivar 'Hokkai100', and its spear weight is slightly larger and spear emergence is earlier. 'Zuiyu' is an all-male cultivar, although up to 30% of plants bear berries in some years. The number of seeds, however, is very small. The color of spears is similar to that of 'Hokka i100' . Spear-head t ightness and spear uniformity are better than those of 'Hokkai100'. Anthocyanin pigmentation in leaves is slightly weaker than that of 'Hokkai100'. Plant height is larger than that of 'Hokkai100' and 'UC157'. 'Zuiyu' is a cultivar for green asparagus production, and it is suitable for the cold upland area in Honshu and in Tohoku and Hokkaido regions.