Evaluation of Ten Elite Nigerian Cassava (Manihot esculenta Crantz) Cultivars for Somatic Embryogenesis and Regeneration Potentials
F. A. Nkaa *
Department of Plant Science and Biotechnology, Michael Okpara University of Agriculture, Umudike, Abia State, Nigeria.
E. E. Ene-Obong
Department of Genetics and Biotechnology, University of Calabar, Cross River State, Nigeria.
N. J. Taylor
International Laboratory for Tropical Agricultural Biotechnology now IICI Trait Improvement Laboratory, Donald Danforth Plant Science Center, St. Louis MO, USA.
C. M. Fauquet
International Laboratory for Tropical Agricultural Biotechnology now IICI Trait Improvement Laboratory, Donald Danforth Plant Science Center, St. Louis MO, USA.
C. N. Egesi
Biotechnology Programme, National Root Crops Research Institute, Umudike, Abia State, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
Development of an efficient regeneration system is one of the basic requirements for cassava genetic transformation. Ten elite Nigerian cassava cultivars consisting of seven improved genotypes and three local landraces were evaluated for their ability to produce somatic embryos in vitro. Responses of these cassava cultivars were compared with that of a model cultivar TMS 60444 known for its potential in somatic embryo production. Somatic embryogenesis in cassava is variety dependent probably due to its recalcitrant nature to in vitro manipulations. Production of somatic embryos in cassava is of two kinds – organized embryogenic structure (OES) and friable embryogenic callus (FEC). All the ten cassava cultivars screened produced organized embryogenic structures on DKW induction medium supplemented with 20 g/l sucrose, 8 g/l Difco noble agar and 50 µM Picloram. Friable embryogenic callus generation in cassava is usually achieved by subsequent transfer of the high quality OES formed to another induction medium Gresshoff and Doy (GD) medium supplemented with 20 g/l sucrose, 50 µM Picloram and solidified with 8 g/l Difco noble agar. Out of the ten cassava cultivars screened only four possessed the capacity for FEC production. Among the ten cassava cultivars screened for somatic embryogenesis, more than half of them had the potential for plantlet regeneration from the two types of somatic embryos.
Keywords: Friable embryogenic callus, in vitro, manihot esculenta, organized embryogenic structure, picloram, somatic embryogenesis