Stable transformation of soybean by electroporation and root formation from transformed callus.

Soybean protoplasts from a number of commercially important cultivars have been genetically engineered by way of electroporation using chimeric genes coding for resistance to the aminoglycoside antibiotics kanamycin and G418. Effective electroporation conditions were determined by monitoring transient expression from aminoglycoside 3'-phosphotransferase II (APHII) expression plasmids. Electroporation of protoplasts with a chimeric APHII gene and subsequent selection on media supplemented with kanamycin resulted in the recovery of calli resistant to the antibiotic. Enzyme assays for APHII activity and Southern blot hybridization confirmed the expression of the foreign DNA and its stable integration into the soybean genome. Root formation was induced from transformed calli, and these roots maintained expression of the APHII gene.