Abstract
”Tanbaguro” is a local variety of Japanese soybean (Glycine max) that is characterized by large seed size and a black seed coat. We intended to determine a method for determining the geographic origin of Tanbaguro seeds by their inorganic element composition. Seed samples of 48 Tanbaguro varieties and eight ”non-Tanbaguro” black soybean varieties cultivated in different years were collected in Japan and China. Eight inorganic elements (Al, Mn, Fe, Ni, Cu, Zn, Sr and Ba) of these samples were estimated using ICP-AES (Inductively coupled plasma atomic emission spectrometer). Significant differences were observed between Japanese and Chinese samples in the contents of four elements (Al, Fe, Cu and Sr). Principal component analysis samples could generally be divided into two groups : those cultivated in Japan and those cultivated in China. Various combinations of inorganic elemental contents were used to perform the linear discriminant analysis (LDA). LDA performed by eight elements classified with a confidence of 96%, and country of origin could be predicted with confidence of 100%. Even when four elements (Al, Mn, Sr and Ba) were used, it was possible to distinguish whether the country of cultivation was Japan or China. LDA performed by Al and Fe contents, selected by stepwise discriminant analysis, classified and predicted with a confidence of only 89% and 79%. However, since all samples cultivated in China could be correctly classified and predicted, this discriminant model was useful for the screening of samples. Therefore, the applicability of this method for determining the geographic origin of Tanbaguro bean varieties was demonstrated.
