Optimization of culture conditions for in vitro rooting of argan (Argania spinosa L.)]

The root system produced of in vitro organ plantlets is of poor quality and not efficient for the transfer to out-door conditions. To overcome such problems, experimentation was undertaken where the effects of growth regulators, nitrogen, sugar, activated charcoal and coconut fiber were tested on root induction and elongation. Modified Murashige and Skoog with half strength salt was used as a basal medium. Root induction (85%) with a mean of 16 roots per explant was obtained when shoots were grown, under dark conditions for 14 days, with a combination of two auxins (IBA and NNA), added at equal concentrations (5 mg.L-1). Secondary roots, 10 cm long, were initiated in 12% of the cultures in presence of 5 g.L-1 activated charcoal. Further improvements in the growth of the primary and secondary roots were obtained when semi-solid medium was substituted with a substrate composed of coconut fibers (80 g) mixed with semi-solid medium (35 mL) and agar (2.5 g.L-1).