Improved and reliable plant regeneration and Agrobacterium -mediated genetic transformation in soybean ( Glycine max L.)

An efficient plant regeneration and transformation system is a prerequisite for soybean crop improvement. To establish such a regeneration system for soybean genotype JS 335, the combination of plant hormones benzyladenine purine (BAP), indole-3-butyric acid (IBA) and kinetin (Kn) at a concentration of 3.0 mg L −1 , 0.2 mg L −1 and 0.5 mg L −1 , respectively, produced the best results using the whole cotyledonary nodes as explants. Furthermore, there is a necessity to improve the efficiency of transformation for gene function studies and to develop soybean transgenics with new traits. There have been decades of research in the field, nonetheless, due to the recalcitrant nature of soybean, the transformation efficiency continues to remain low. This study used the Agrobacterium -mediated cotyledonary node transformation system and the bar gene as the plant selectable marker coupled with glufosinate as a selective agent. Explants were cultured on Gamborg’s B5 medium supplemented with 1.67 mg L −1 BAP and glufosinate at 3 mg L −1 for the selection of transformants. The transformation status of the primary transformants (T 0 ) and T 1 generation progeny was confirmed by various molecular analyses. Using the cotyledonary node explants and the bar selection system, we have successfully developed an improved and reliable transformation system than the earlier reported work on Indian genotypes of soybean, and this established protocol could provide a useful tool for genetic improvement and functional genome studies in soybean.