Transient auxin treatment for in vitro rooting of microcuttings of Acacia tortilis subsp raddiana

An auxin in vitro pretreatment (IBA or NAA at 10 to 20 mg L-1) combined wit h a low concentration of Kinetin (0.01 mg L-1) during 10 or 20 days allowed to improve the rooting (number and root length) of Acacia tortilis raddian a microcuttings after transfer on Lloyd and Mc Cown medium (WPM) without ho rmone. After microcuttings transfer in expression medium, 56% are rooted an d the rooting frequency can reach 80% after pretreatment with IBA at 10 mg L-1. Measurements made after 28 days show that the auxin type used for indu cing rhizogenesis has a significant effect, both on rooting percentage and rooting system morphology. For 80% of plantlets, the number of roots is low with NAA (1 to 5) but roots are strong and orthotropic (4.5 to 5 cm on ave rage) when with IBA roots are numerous (10 to 15), but thin and plagiotropi c (3 to 3.7 cm) for 68% of rooted plantlets.