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Selection and in-vitro propagation of five cassava (Manihot esculenta, Crantz) cultivars
Thirteen cassava cultivars were collected from farmers in the Greater Accra Region using a structured questionanire. Five cultivars namely, Ankrah, Bosom nsia, Biafra, Santom and Afisiafi were selected based on popularity, duration to maturity and tolerance to African Cassava Mosaic Virus (ACMV) disease. The cultivars were propagated in vitro using meristem, multiple shoots culture, and somatic embryogenesis. Meristematic explants were cultured on Murashige and Skoog (1962) basal salts and vitamins (MS) amended with NAA 0.1 mg/l, GA3 0.1 mg/l BA (0.0-0.15 mg/l BA). There was profuse callus formation in all the cultivars. The optimal concentration for shoot proliferation was 0.10 mg/l BA or 0.15 mg/l BA. With reduced NAA and GA3 concentrations (0.02 and 0.04 mg/l respectively) in the culture medium BA 0.05 mg/l was optimum with 100% and 46% shoot regeneration respectively in Bosom nsia and Santom compared to 37% and 0% in the ptevious treatment. All the selected cultivars formed multiple shoots from single bud cutting of in vitro plantlets. However, the number of apical shoots formed was dependent on BA concentration in the medium. Embryogenic calli formation on MS amended 2,4-D 0.0-16 mg/l depended on the type of explants. For greenhouse grown plants development of embryogenic calli from young leaf lobe and apical meristem explants was significantly higher than stipule explants. However, none of the calli were able to induce primary embryos when transferred to a maturation medium (MS plus 0.1 mg/l BA). Similarly embryogenic calli formation from tissue-cultured young leaf lobe explants on the same media were high in all the 2,4-D treatments. Subsequent production of primary embryo was low on the maturation medium and was found to depend on the cultivar and 2,4-D concentration. Somatic embryo formation was higher on 2,4-D 16 mg/l medium than on 4 mg/l or 8 mg/l 2,4-D medium. Santom produced the highest percentage of embryo (25%) among the cultivars used. Embryogenic calli which did not form somatic embryos formed roots which depended on the 2,4-D concentration of the induction medium.
JOURNAL OF THE GHANA SCIENCE ASSOCIATION Volume 1 Number 3, July (1999) pp. 31-41