Differing Sucrose Requirements for In-vitro Conservation of Cassava Genotypes

Field conservation of vegetative propagated crops poses a major problem to curators of germplasm, especially in developing countries. An alternative method to ensure security of germplasm is the use of tissue culture techniques in media formulated for slow growth. However, tissues of plant species may require different nutrients for optimum growth. The objectives of this study were to a) assess the effects of sucrose on the performance of different cassava genotypes and b) recommend sucrose levels for in-vitro conservation of the genotypes. Four sucrose levels (0, 10, 20, and 30 g l-1) and apical meristems of five cassava genotypes (Bankye Hemaah, Bankye Botan, Tek Bankye, Doku Duade, and Essam Bankye) cultured in-vitro was studied at the Kwame Nkrumah University of Science and Technology’s plant biotechnology laboratory. Growth media were prepared using hormone-free Murashige and Skoog (MS) basal media formulation. Inoculated cultures were exposed to 16 hours of light and 8 hours of darkness with light illuminance of 3500 lux and also maintained at 24±2°C temperature and relative humidity of 70%. All genotypes showed a direct regeneration without callus formation. Generally, sucrose enhanced the growth performance of plantlets; however, the genotypes responded differently to sucrose in leaf formation, plant height, and rooting ability with time. For long term conservation, growth medium must sustain the health of plantlets with infrequent need for sub-culturing. As such, sucrose levels of 10 g l-1 for Essam Bankye, 20 g l-1for Doku Duade and Tek Bankye, and 30 g l-1 for Bankye Hemaa and Bankye Botan were the recommended rates for in-vitro conservation.