[Factors influencing agrobacterium-mediated transformation of maize elite inbred lines]

Using the maize elite inbred lines 9046, Qi319, 414, Mo17 as target genotypes, a highly efficient transformation system was developed based on the study of factors influencing the Agrobacterium-mediated maize transformation. The results showed that the immature embryos of 1.0-2.0 mm in length were optimal transformation explants. Inclusion of acetosyringone (200 micromol/L) and ascorbatic acid (50 mg/L) in both infection medium and co-cultivation medium led to a significantly increase in the transformation efficiency. However, high osmotic treatment on the explants before inoculation didn't improve transformation efficiency. Delaying selection was beneficial to the survival of resistant calli. Using the optimized transformation procedure, 42 PCR-positive transgenic plants were obtained from the 4 elite inbred lines and the frequency of PCR-positive plant ranged from 1.71%-4.09%. The integration of the transgenes into the maize nuclear genome was confirmed by PCR analysis using bar- and gus-specific primers and by Southern blot using gus- specific probe. Most of transgenic plants (71.4%) had one copy of T-DNA insert. The establishment of the transformation system in maize provides an efficient way for transferring useful foreign genes to maize plants.