In vitro regeneration of selected commercial Tanzanian open pollinated maize varieties

Four Tanzanian open pollinated maize varieties namely; Kito, Situka M-1, Staha and TMV-1 were regenerated in vitro using immature zygotic embryos as ex-plants. Callus induction was achieved using Murashige and Skoog (MS) basal medium supplemented with 1, 1.5, 2 or 2.5 mg/l of 2, 4-D. Callus induction was significantly affected by the genotype of the varieties. Among the varieties tested, Kito, Situka M-1 and Staha had significantly higher callus induction frequency of 84.4, 92.7 and 88.7%, respectively compared to TMV-1 (43.3%). Embryogenic callus induction percentage was significantly influenced by the genotype, 2, 4-D concentrations and their interaction effect implying differential response of the genotypes to 2, 4-D concentrations. Among the genotypes tested, Kito gave significantly (p<0.05) the highest embryogenic callus frequency of 69.5%. Great variations were observed among the genotypes with regard to regeneration frequencies. Staha was comparatively the most regenerable variety with RF of 32.6% than even Kito which had the highest callus induction and embryogenic callus formation. MS medium amended with 1 mg/l 2, 4-D was observed to be the optimum formulation for the induction of embryogenic calli for genotypes tested in this study. Using this regeneration system Situka M-1, Staha and TMV-1 can now be improved against various production constraints through genetic engineering.Key words: 2, 4-dichlorophexyacetic acid, embryogenic callus, immature zygotic embryos, regeneration frequency, somatic embryos, Tanzanian open pollinated maize

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

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 embryosharvested 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. Consequentlytropical 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 zygoticembryos 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 of2,4-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  itamins supplemented with 2 mg l-1of 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