Rizogênese in vitro e aclimatização de plantas micropropagadas de Peltophorum dubium (Sprengel) Taubert

Abstract

Peltophorum dubium (Sprengel) Taubert, is native forest species of Brazil, and due to its rusticity and fast growth presents great ecological importance for projects to recovery of degraded areas. The present study proposes to optimize the phases of in vitro rhizogenesis and in vitro and ex vitro acclimatization of Peltophorum dubium micropropagated plants. In the in vitro rhizogenesis, four experiments were carried out, in which the micropropagated buds were evaluated in relation to the effects of culture media [composed of WPM nutrient medium reduced to half the concentration of the salts (WPM/2) in presence (30 g L-1) or absence of vermiculite previously autoclaved or not], of pH values (4,8; 5,8; or 6,8), in agar concentrations (4,0; 5,5 or 7,0 gL-1), and two seed lots (lot 2010 or lot 2012) explants donors. Two experiments were performed in the in vitro and ex vitro acclimatization, in which the effect of explant donor lots and culture medium used in the rhizogenesis stage were tested. The best results (average of 95%) of rhizogenesis occur in culture medium containing vermiculite, regardless of whether or not it was previously autoclaved, however, neither the different pH levels nor the concentrations of agar tested have a significant effect on in vitro root formation. In acclimatization there are differences in the in vitro performance of the seed lots that originated the initial explants, being the 2012 lot the one that shows the best results. The absence of vermiculite in the culture medium of the rhizogenesis propitiate, in acclimatization, a greater increase in height and vigor, but does not interfere in the survival of the plants. Among the conclusions obtained, the following can be highlighted: the use of vermiculite combined with the nutritive medium WPM/2 favors in vitro rhizogenesis; neither the pH nor the agar influence the in vitro formation of roots; the use of the 2012 seeds lot allows greater development of the explants compared to the 2010 lot. In acclimatization, the absence of vermiculite in the culture medium in the in vitro rhizogenesis stage leads to a better performance, but does not interfere in the survival of the micropropagated plants; and there are differences in the seed lots that originated the initial explants, being the 2012 lot superior. Finally, we emphasize that, in the present work, the increment obtained in the rhizogenesis in comparison to previous works, besides being a consequence of an accumulated experimentation, was due to the use of a lot of seeds with superior performance and, perhaps, the option of not transferring the cultures to fresh culture medium after the first 30 days of in vitro rhizogenesis, which yielded, simultaneously, higher averages of formation and length of roots formed.