Difference of ITS sequences of Akebia plants growing in various parts of Japan

The stem of the Akebia plant, "Mokutsu", is a crude diuretic and antiphlogistic drug. Japanese products prepared from wild Akebia plants cover most of the Mokutsu market. Two Akebia plants, Akebia quinata Decaisne (Aq) and A. trifoliata Koidzumi (At) of Lardizabalaceae, are standardized as Mokutsu in Japanese pharmacopoeia. These two Akebia plants along with A. x pentaphylla Makino (Ap), which is considered a hybrid with the morphology of Aq and At, can be distinguished by DNA sequence analysis of internal transcribed spacers 1 and 2 (ITS) of nuclear ribosome DNA. Here, we report the results of molecular genetic analysis of Akebia plants grown in various wild habitats in Japan. We found that each of three Akebia plants could be distinguished in terms of their locality according to their nucleotide sequence in ITS, specifically at positions 91, 128, 133, 134, and 221. Plants with a comparable habitat had similar nucleotide sequences at these five points. We also found Aq with ITS and nucleotide deletion at position 86 that was distributed only around Awajishima in Shikoku (A), Harimanada (B), and Kinki (C), including the chief production center of Akebia Caulis. The results of these ITS sequences enabled discrimination of plants originating from Akebia Caulis.