Effects of Sowing Time and Temperature during Seed Filling Period on Yield and Seed Isoflavone Content of Soybean Variety

Abstract

We studied the effects of sowing time and temperature during the seed filling period on the yield and seed isoflavone content of two soybean varieties, Suzuyutaka containing an ordinary amount of isoflavone and Tohoku 126 containing a large amount of isoflavone. Tohoku 126 had a higher seed yield than Suzuyutaka regardless of sowing time and planting place. The late sowing soybeans had a higher isoflavone content, but lower seed yield than the standard sowing soybeans. The seed isoflavone content tended to increase by exposure to a low temperature during the seed filling period. The seed isoflavone content of Suzuyutaka grown under the low temperature condition during the latter half of the seed filling period, was similar to that of Tohoku 126 grown under the same condition. Thus the seed isoflavone content of soybean which varies with the variety was greatly influenced by temperature during the seed filling period, especially by the temperature during the latter half of the seed filling period.