Plant Regeneration of Ethiopian Tropical Maize (Zea mays L.) Genotypes

Five Ethiopian tropical maize genotypes were evaluated for their regeneration potential through somatic embryogenesis to establish regeneration system and select regenerable genotypes as prerequisites in applying genetic transformation for improved drought stress tolerance. Immature zygotic embryos were incubated for callus induction on Murashige and Skoog basal salts supplemented with 1.0, 1.5, 2.0 and 2.5 mg L-1 2, 4-dichlorophenoxyacetic acid. The genotypes differed significantly (p<0.01) in callus induction frequency, formation of embryogenic callus, number of shoots per embryogenic callus regenerating plants, percent of embryogenic callus forming shoots and regeneration efficiency. Among the genotypes investigated, [CML387/CML176]-B-B-2-3-2-B [QPM] and Melkassa-6Q had higher capacity in embryogenic callus formation, regeneration efficiency and higher proportion of embryogenic calli forming shoots. Melkassa-6Q and Melkassa-2 produced significantly (p<0.05) higher number of shoots per regenerated embryogenic callus. Higher frequencies of primary and embryogenic callus and regeneration efficiency were obtained from the use of 1 mg L-1 2,4-dichlorophenoxyacetic acid indicating this as optimal level for regenerating these genotypes. Except [CML312/CML206]-B-3-2-1-1-1 fertile plants were regenerated from all genotypes and set seeds which were viable to germinate and produce phenotypically normal plants. Melkassa-6Q, [CML387/CML176]-B-B-2-3-2-B [QPM] and Melkassa-2 were selected for use in genetic transformation.