Plant regeneration through callus initiation from mature embryos of maize (Zea mays L.)

An efficient maize regeneration system was developed using mature embryos. The use of mature embryos from dry seeds possesses several advantages: mature embryos are easy to handle and available throughout the year and in bulk quantities. In this study، mature dry seeds of five maize inbred lines (K126، L105، B73، Mo17 and S61) were used. Embryos were removed from surface-sterilized mature seeds and sliced into halves. They were used as explants to initiate callus on induction medium containing 4 mg/l 2،4-dichlorophenoxyacetic acid (2،4-D). Mature embryos were incubated at 27 °C in darkness. The induction frequency of primary calli was over 90% for all tested inbred lines. Then، the primary calli were transferred onto subculture medium supplemented with 2. 0 mg/l 2،4-D concentrations 0. 2 or 0. 5 mg/l of 6-benzylaminopurine (BA) or Thidiazuron (TDZ) and 10 mg/l AgNO3. Embryogenic callus readily formed plantlets on regeneration medium supplemented with 0. 2 or 0. 5 mg/l BA or TDZ. The regenerated plantlets were transferred to half-strength Murashige and Skoog (MS) medium supplemented with 0. 6 mg/l indole-3-butyric acid (IBA) to develop roots. The frequency of green shoot formation ranged from 18. 3-40. 25%. The highest mean percent (40. 25%) was observed for S61 genotype on medium containing 0. 2 mg/l TDZ and 10 mg/l AgNO3. This efficient regeneration system provided a solid basis for genetic transformation of maize.