Abstract
The soybean breeding program for high isoflavone content started in 1996 at the Kariwano Branch of the National Agriculture Research Center for Tohoku Region. The isoflavone content of seeds of more than 2,000 soybean [Glycine max (L.) Merr.] and wild soybean (Glycine soja Sieb. et Zucc.) were evaluated using high-performance liquid chromatography (HPLC) from 1996 to 2002 to select parents for cross-breeding and to investigate the yearly change of isoflavone content. Isofavone content ranged from 23.5 to 848.5 mg/100gDW and was generally lower in early maturing than in medium and late maturing groups. Moreover, the difference in isoflavone content among varieties and lines was small in the early maturing group but was large in the medium and late maturing groups. The ratio of the content of daidzein to that of the total isoflavones ranged from 18.6 to 81.7% and stable in each germplasm. Moreover, the yearly coefficient of variation of total isoflavone content investigated for six years by using 18 varieties was 13.1-60.7%, and did not correlate with isoflavone content. In addition, it did not correlate with the seed coat color, the cotyledon color, the weight of 100 seeds and the crude protein content in all germplasms used. The seeding time, i. e., regular or late season culture, was significantly correlated with isoflavone content in 15 varieties. These results suggest the possibility of the breeding and cultivation of soybean with a high isoflavone content soybean.
