In vitro REGENERATION OF SOME ETHIOPIAN MAIZE (Zea mays L.) LINES AND VARIETIES FROM IMMATURE EMBRYOS THROUGH CALLUS INDUCTION
TAREKEGN GEBREYESUS ABISSO *
College of Life Science and Bio-engineering, Beijing University of Technology, Beijing 100124, P. R. China
BEKELE CHAKISO GUGERO
Department of Biology, College of Natural and Computational Science, Wachemo University, Hossana, P.O.Box 667, Ethiopia
*Author to whom correspondence should be addressed.
Maize is an important food crop in Ethiopia. Among major factors contributing to the low productivity of maize in Ethiopia include, absence of improved varieties and significant yield reduction due to high incidences of biotic and abiotic stresses. Success in genetic transformation requires efficient in vitro regeneration protocols. However, inadequate information is available on in vitro regeneration of maize varieties/lines developed for Ethiopian climate. Therefore, this study was initiated to optimize the in vitro regeneration protocols for some inbred lines and open pollinated maize varieties from immature embryos. Immature embryos evaluated for their ability to form callus were cultured in N6 medium and incubated at room temperature in dark to initiate callus. Embryogenic calli were transferred from callus maintenance medium to embryo maturation medium supplemented with 2 mg/l glycine, 1 mg/l NAA and different levels of sucrose (55, 60, 65 or 70 g/l). Matured somatic embryos were subcultured in shoot regeneration medium consisting of MS medium supplemented with 2 mg/l glycine, 2% sucrose and different levels (0, 0.1, 0.2 and 0.3 mg/l) of BAP. Roots were induced by subculturing individual shoots on half strength MS medium supplemented with 2 mg/l glycine, 2% sucrose and different levels (0, 0.1, 0.2 and 0.3 mg/l) of NAA. Immature embryos harvested in between 16-20 days after pollination, depending on the variety responded better than early harvested immature embryos for average callus induction. Better plant regeneration was obtained at basal (hormone free) MS medium. Better root formation was at 0.1 mg/l NAA with average of 2.82- 4.50 roots per shoot. Regenerated plantlets were successfully acclimatized in greenhouse and field conditions with survival rates of 83.7% and 75.6% respectively. This study established a regeneration scheme for maize lines/ varieties via somatic embryogenesis from immature embryos and high performing maize verities/ lines were identified.
Keywords: Acclimatization, immature embryos, maize, medium, plantlet regeneration