Soybean (<i>Glycine max</i>) Transformation Using Immature Cotyledon Explants

Agrobacterium tumefaciens-mediated transformation of soybeans can be accomplished using immature zygotic cotyledons as target tissues providing an alternate explant to embryogenic tissue cultures, proliferating meristems, and cotyledonary nodes. The immature cotyledon method includes direct induction of transgenic somatic embryos from the explant plated on selective media after cocultivation, followed by maturation and regeneration of individual somatic embryos into whole plants. Although this method has been improved to be simple, rapid, reproducible, and applicable to a range of cultivars in different maturity groups, the transformation efficiency (Southern-positive, independent plants produced per 100 immature cotyledon explants) is 1.7% and needs to be further increased to make this a robust soybean transformation system. Further refinements of cocultivation conditions, tissue culture, and selection of regenerated transgenic plants will probably result in increases in transformation efficiency.