Abstract:

Soybean (Glycine max (L.) Merrill) is one of the recalcitrant crops to be manipulated in vitro. To improve Agrobacterium-mediated soybean cotyledonary node transformation efficiency, a new solidliquid medium selection system based on using the bar gene as the selectable marker has been developed. The cotyledonary nodes were first cultured in MS solid medium modified with 2 mg/L 6-BA and 5 mg/L glufosinate for two weeks, and the surviving explants were transferred into a liquid selection medium with 2 mg/L glufosinate and 0.01 mg/L thidanzuron (TDZ) instead of 6-BA for further selection. The liquid medium was changed every week until the transgenic shoots were regenerated from the liquid selection medium. Several factors affecting the transformation efficiency have also been evaluated. GUS assay and Southern blotting analyses confirmed the integration of the transgenes into the soybean genome. This transformation system is genotype-independent and efficient, and has less escape due to the tight selection.

Key words: soybean, cotyledonary node, Agrobacterium tumefaciens, transformation, liquid selection