Optimization of somatic embryogenesis and embryo germination in soybean

Summary Somatic embryos of soybean [Glycine max (L.) Merr.] are induced on immature cotyledons explanted onto a medium containing moderately high levels of auxin. Germinability of embryos is related to morphologic normality, and both are reduced by excessive exposure to auxin during the induction process. Shoot meristem development was improved by reducing exposure of cotyledonary explants from 30 to 10 to 14 d on 10 mg/liter α-naphthaleneacetic acid (NAA). A 3-d exposure was sufficient to induce embryos, and embryo frequency was not significantly increased by exposures to NAA for more than 1 wk. Embryo frequency was enhanced, however, by transfer after 9 d to fresh medium containing 10 mg/liter NAA. Germination of morphologically normal embryos was achieved without growth regulators, after maturation for 1 mo. on hormone-free medium and desiccation for 1 wk in a sealed, dry container. This research was funded by Lubrizol Genetics, Inc., Madison, WI.