S Preparation
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Ten Allium (A.) fistulosum species, six sp … Ten Allium (A.) fistulosum species, six spring onion cultivars, two scallions, and two Japanese-leek cultivars, rakkyo (A. chinense) and Oriental garlic (A. tuberosum), were purchased from a grocer in Kawasaki, Japan or harvested in a Japanese field (see Table 1 and Additional file 2). After removing the roots, a 10-cm length of the sheath and the basal plate of each plant sample were collected and chopped with stainless steel surgical blades (Feather, Tokyo, Japan). Out of the A. fistulosum cultivars, four were grown by applying a method (hilling) similar to that used for growing the leek A. ampeloprasum var. porrum to obtain longer white stems for consumption in Japan (Fig. 1f, g, h, l). Each sample was immediately frozen in liquid nitrogen and kept at −80 °C until use. As the group of samples of Mikata spring onion (class01) was gathered center of the PCA score scatter plot (Fig. 4), this cultivar was chosen as the control. , this cultivar was chosen as the control.
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