Further improvement of N6 medium for callus induction and plant regeneration from maize immature embryos

To explore the possibility to improve N6 medium for callus induction and plant regeneration from maize immature embryos, comparative experiments were conducted to screen the optimal calcium concentration for the callus induction medium and the subculture medium modified from N6 medium and to examine the effects of uniconazole and ABT root promoting powder supplement on plant regeneration and root generation. According to the results, the calcium concentration of N6 medium was increased from 1.13 to 5 mmol/l for callus induction and subculture. Uniconazole from 0.25 and 0.5 mg/l and ABT root promoting powder of 0.5 mg/l were suggested to be supplemented to the regeneration medium and the root generation, separately. On these improved media, the frequency of callus induction, the relative proliferation rate of callus subculture, the regeneration rate and the average root biomass of the regenerated plantlets increased significantly. All these improvements facilitate the establishment of acceptor system from elite parental inbred lines of commercial hybrids and provide a solid basis for transgenic manipulation of maize. Keywords: ABT root-promoting powder, calcium, callus induction, immature embryo, maize, N6 medium, plant regeneration, uniconazole