Reproducible transformation in two grain legumes--soybean and azuki bean--using different systems

Two plasmid vectors were introduced into soybean (Glycine max (L.) Merr.) and azuki bean (Vigna angularis Willd. Ohwi and Ohashi) using different transformation systems. Azuki bean epicotyl explants were prepared from etiolated seedlings and co-cultivated with Agrobacterium tumefaciens for 2 days. Adventitious shoots were developed from the callus of the explants on a regeneration medium containing hygromycin, and the shoots were excised and transferred to a rooting medium containing hygromycin at the same concentration. Rooting shoots were transferred to soil and grown in a glass-house to produce viable seeds. PCR analysis confirmed clearly the presence of the hpt gene in most of the azuki beans regenerated under hygromycin selection. A soybean embryogenic suspension culture was generated from immature cotyledons, and used for the introduction of plasmids by particle bombardment. Hygromycin-resistant embryogenic clones were isolated after 8 weeks of hygromycin selection, and then the green clones were matured on the differentiation medium. After desiccation, the embryos were germinated on the rooting medium, and the plants were transferred to soil in a glass-house. More than 50% of the regenerated soybean plants tolerant to hygromycin yielded the hpt fragment on PCR analysis. The azuki bean transformants were obtained more rapidly and with higher efficiency than the soybean transformants.