XVI International Botanical Congess

Photoperiod is an important factor in the flowering of soybean [Glycine max (L.) Merr.]. Typically, soybeans develop flower buds rapidly under short day conditions (SDC) while several soybean varieties in low latitude area were reported to have a late flowering, or long juvenile (LJ) trait under SDC. It is still unclear, however, when floral initiation starts in LJ varieties. In this study, we investigated the differences between conventional juvenile (CJ) types and LJ types of soybean isogenic pairs in floral initiation under SDC (12 h L, 25 C). In LJ lines, the first floral buds were observed later and on the upper nodes than CJ lines. We concluded that under SDC, LJ soybeans are late not only in flowering, but also in floral initiation. This suggests that these LJ lines have longer juvenile phase than CJ lines.