In vitro rhizogenesis on shoots of Luehea divaricata Mart. & Zucc

Luehea divaricata is a native forest species of the Atlantic Rainforest biome widely used for the recovery of degraded areas. Its wood can be used for the most diverse purposes, which has contributed to a reduction in its natural populations and is causing difficulties to find seeds with genetic, physiological and sanitary quality for using in the seedling production. Therefore, micropropagation is an alternative with the potential for producing seedlings to use in environmental projects. The objective of this work was to optimize the in vitro rhizogenesis processes, in which different concentrations of salts of the WPM nutritive medium were initially evaluated. Next, Indolbutyric Acid (IBA) was added to the medium as the "pulse" treatment for 15 days, and Naphthaleneacetic Acid (NAA) in both cases to the in vitro culture in WPM nutritive medium was reduced to half of its initial concentration (WPM/2) and the rhizogenesis effects were analyzed. Finally, the effect of combining vermiculite volumes with WPM/2 was also analyzed. The results showed that the WPM/2 medium produced the most promising results of the in vitro establishment (98%), and the highest average (40.52%) regarding the formation of primary adventitious roots after 45 days of in vitro culture was observed regardless the concentration of salts in the medium. The "pulse" treatment after 30 days of in vitro culture, regardless of IBA concentration, resulted in an average of only 25.18% of primary adventitious root formation. The combinations of 20 mL + 15 cm(3), 20 mL + 30 cm(3) and 30 mL + 30 cm(3) of nutritive medium and vermiculite, respectively, were the most favorable for forming second order lateral adventitious roots, providing averages between 38 and 49.5% after 45 days of in vitro culture. Therefore, in order to optimize the rhizogenesis process of Luehea divaricata, it is indicated to grow the in vitro culture for 45 days in WPM/2 nutritive medium combined with vermiculite without the addition of auxins.