Productive Differences between Male and Female Plants in White Asparagus Production Using the Rootstock-planting Forcing Culture Technique

摘要

This study analyzes the first large-scale asparagus experiment in Japan to examine the productive differences between male and female plants using the rootstock-planting forcing culture technique. This technique has recently been developed in Japan and uses dug-up rootstocks for one-season harvests during the off-crop season. As larger spears and early sprouting are especially favored in this culture for higher yield, it is important to clarify and evaluate the productive traits of the male and female plants. We conducted collaborative research among eight institutes from Hokkaido to Kyushu to examine plants grown at different cultivation sites. There were two digging-up months and different low-temperature backgrounds. Plant rootstocks sourced from the eight different sites used in the experiment were cultured in an abandoned tunnel in Nagano Prefecture, Japan, in a large area with uniform temperature and high humidity throughout the year, and their white spears were harvested. The results of this study show that the female plants had a significantly higher rootstock weight, weight per spear per plant, and weight per early spear per plant, whereas the male plants had a significantly higher total spear number per plant, early spear number per plant, and significantly fewer days to first harvest. No significant differences were observed in soluble solid contents of roots, total spear weight per plant, or early spear weight per plant. It seems that male plants have a tendency to sprout earlier than female plants in response to reduced accumulated low temperature hours, and also to produce a higher total spear number per rootstock weight and total spear weight per rootstock weight. The ranges of most of the productive traits analyzed in this study completely overlapped between the sexes. However, female plants showed higher variation in weight per spear per plant and weight per early spear per plant.