In vitro Culture of Immature Soybean Embryos

Immature embryos of soybean [Glycine max (L.) Merr., cvs. Beeson, Chippewa, Swift, and Tonica] ranging from globular to cotyledon stages were cultured in vitro. A variety of media consisting of 24 combinations of basic media salts, growth regulators, and carbon sources was tested in conjunction with initial exposure of cultures to light or darkness. The best combination tested was B5 medium supplemented with 0.1 mg · 1(-1) indole-3-butyric acid (IBA) and an intitial exposure to darkness for two weeks. The survival rate increased progressively with embryo age and stage of development. Approximately 10% of late globular-early heart stage embryos survived to sexual maturity and produced seed whereas virtually 100% of the cotyledon stage embryos produced plants which flowered and set fruit. Approximately 25% of the globular stage embryos were induced to initiate a hypophysis but they subsequently either formed callus or died within a week. Although plants resulting from in vitro culture of immature embryos were diminutive, they otherwise were morphologically normal and produced seed of normal size and weight, as did their progeny.