Effect of Osmotic Regulators on In Vitro Conservation of Brazilian Ginseng, Potato and Cassava Germplasms

Slow growth in vitro conservation is widely used in the conservation of germplasm of various species. Changes in the chemical conditions of the culture medium, using e.g., osmotic regulators, has been used as a strategy for reducing the in vitro plant metabolism and prolonging the cultivation period. The objective of this study is to evaluate the use of osmotic regulators on the in vitro conservation of Brazilian ginseng (Pfaffia glomerata), potato (Solanum tuberosum) and cassava (Manihot esculenta) germplasms for reducing the in vitro plant growth and prolonging the cultivation period. Nodal segments from in vitro grown plantlets were cultured on MD medium (modified MS salts and vitamins, 0.02 mg/L BAP, 0.01 mg/L NAA, 0.1 mg/L GA(3)) for cassava or MS0 medium (MS medium without growth regulator) for Brazilian ginseng and potato, added sorbitol (0, 20, 40, or 60 g/L) or mannitol (0 to 20 g/L) as osmotic regulator, maintained for 9 months at 20 degrees C and 45 mu mol m(-2) s(-1) photosynthetic photon flux density of light intensity with a 12-h photoperiod. Effects of the osmotic regulators were different depending on the culture period and species. The sorbitol at concentrations of 20 and 40 g/L delayed the shoot growth and could be used for the in vitro conservation of potato and Brazilian ginseng germplasms. For the conservation of cassava germplasms, mannitol at a concentration of 20 g/L was suitable as an osmotic regulator.