Optimization of Agrobacterium-mediated transformation parameters for sweet potato embryogenic callus using beta -glucuronidase (GUS) as a reporter

Agrobacterium-mediated transformation factors for sweet potato embryogenic calli were optimized using beta -glucuronidase (GUS) as a reporter. The binary vector pTCK303 harboring the modified GUS gene driven by the CaMV 35S promoter was used. Transformation parameters were optimized including bacterial concentration, pre-culture period, co-cultivation period, immersion time, acetosyringone (AS) concentration and mannitol treated time. Results were obtained based on the percentage of GUS expression. Agrobacterium tumefaciens strain EHA105 at concentration OD sub(600 nm) = 0.8 showed the highest virulence on sweet potato embryogenic callus. Four days of pre-culture, four days of co-cultivation, 10 min of immersion, 200 mu M acetosyringone and 60 min of mannitol-treated embryogenic callus gave the highest percentage of GUS positive transformants.