1. 1Subtropical Field Science Center, Faculty of Agriculture, University of the Ryukyus, Nishihara Cho, Okinawa, 903-0213, Japan
2. 2Okinawa Agricultural Experiment Station, Itoman Shi, Okinawa, 903-0814, Japan
3. 3Graduate School of Medicine, University of the Ryukyus, Nishihara Cho, Okinawa, 903-0215, Japan