Full Length Research Paper

Regeneration of tropical maize lines (Zea mays l.) from mature zygotic embryo through callus initiation

D. Zerihun Abebe¹, Wondyifraw Teffera¹ and Jesse S. Machuka²*

¹Agricultural Research Center, Ethiopian Agricultural Research Institute, P. O. Box 192, Jimma, Ethiopia.

²Department of Biochemistry and Biotechnology, Kenyatta University, P. O. Box 43844, Nairobi, Kenya.

*Corresponding author. E-mail: Machuka@mitsumi.net or Machuka@ku.ac.ke. Tel: +251-20-810245. Fax: +254-20-811575.

Abbreviations: 2,4-D, 2,4-dichloroaceticacid; BAP, benzyl aminopurine; DAP, days after pollination; KT, kinetin; KAT, Katumani and CML 216, CIMMYT maize line 216.

Accepted 4 January, 2008

The use of immature zygotic embryos as an explant for maize regeneration has been hampered by the strictly limited suitable duration of immature embryos for culture. In contrast, mature zygotic embryos harvested from dry seeds are ubiquitous. However, generally mature embryos and especially tropical maize genotypes have been considered as the most recalcitrant for tissue culture work. Consequently tropical maize regeneration from mature embryos has not been reported so far. Here, we report successful regeneration of one inbred and one open pollinated tropical maize line from mature zygotic embryos using split seed technique. The maximum average callus induction recorded using LS basal salts and B5 vitamins supplemented with 3 mg l^-1 2,4-D alone was 90% and 52.5% when same level of 2,4-D was combined with Kinetin. A maximum of 75.6% Type II and 62.3% Type I callus was produced after maintaining calli on media composed of LS basal salts and B5 vitamins supplemented with 2 mg l^-1 of 2,4-D. The frequency of regenerable calli induced was 21.14% for CIMMYT maize line 216 and 16.51% for Katumani. The number of shoots regenerated per callus induced on single split seed ranged from 1-5.

Key words: Maize tissue culture, scutellum, plumule, organogenic callus, embryogenic callus.