In vitro propagation of the gum arabic tree (Acacia Senegal (L.) Willd.) 1. Developing a rapid method for producing plants

The method described herein permitted production of three to four micropropagules of Acacia Senegal from one uninodal explant. The explants were taken from plants produced either in a sterile environment or during four years in a greenhouse. Zeatin or 6-benzylaminopurine (BAP) were mixed, at different concentrations, with Murashige and Skoog's medium (MS) of which the amount of macroelements was divided in half (MS mod.). At a concentration of 5.0×10(-5) M, zeatin produced a better multiplication rate after 60 d for the two types of plant stock than did BAP. A two stage process was necessary to obtain a rooting rate of the small cuttings close to 100%. The first stage, called induction, consisted of leaving the cuttings for 6 to 12 d on a Jordan's medium (JN) of which the amount of macroelements was reduced by half (JN mod.) and in which NAA at a concentration of 5.0×10(-5) M was added. The second stage, called root extension, required that the small cuttings be planted on this second hormone-free medium. Roots appeared after a few days. Acclimatization in a greenhouse occured with a survival rate of close to 100% when the rooted in vitro plants were transplanted to pots containing a mixture of vermiculite and top soil (1∶1; v/v).