EFFICIENT TRANSFORMATION OF SCUTELLAR TISSUE OF IMMATURE MAIZE EMBRYOS

An efficient transformation system for maize was established by improv ing transformation conditions for the particle bombardment of the scut ellar tissue of immature embryos. Particle bombardment was carried out using constructs containing the pat gene as the selection marker and a PDS 1000/He gun (Biorad). Transformation parameters, such as the amo unt of gold particles used per bombardment, particle velocity, precult ure time of the scutellum prior to bombardment and osmotic treatment o f the target tissue before and after bombardment, were analysed. Ferti le transgenic regenerants of the maize inbred lines H99, A188 and Pa91 and the crosses A188 x H99 and Pa91 x H99 were selected on Basta-cont aining medium. The transformation frequency was between 2% and 4%. A t otal of 29 transgenic plant lines was obtained and verified with South ern blot analysis. All of the transgenic plants were fertile and set s eeds. The R1 progeny of single plants was analysed. A Mendelian segreg ation of the transgenes was observed for all of the transformants test ed. For 1 candidate, stable inheritance and stable expression of the t ransgenes were followed up to the R-4 generation.