Desinfestação e estabelecimento in vitro de Louro-pardo (Cordia trichotoma (Vell.) Arrabida ex Steudel)

Abstract

In order to meet the growing demand for good quality wood, studies have been carried out. The Louro-pardo (Cordia trichotoma (Vell.) Arrabida ex Steudel) is a native forest species, with good quality wood and wide application. The production of seedlings for comercial plantations of louro-pardo by means of seeds is not the best strategy, due to recalcitrance, slow and irregular germination and heterogeneity obtained by sexual propagation. Vegetative propagation is an alternative to obtain uniform and high-standard plantations. Micropropagation is an alternative to meet the demand for seedlings of this species. In order for micropropagation to be carried out, it is necessary to have an efficient protocol for disinfestation and in vitro establishment, enabling subsequent steps. In this sense, the presente study aimed to evaluate different strategies for disinfestation and in vitro establishment of louro-pardo. The explants used were nodal segments from trees of high productivity, located at UNEPE Caprinovinocultura, at UTFPR Campus-DV. Sealing and sterility assays and in vitro disinfestation and establishment were performed. The sealing and sterility test tested four sealing methods: Aluminum foil (T1), cotton cap (T2), kimble cap (T3) and Falcon tube (T4). Five repetitions of each treatment were performed. Three disinfestation and in vitro establishment trials were carried out. The first trial evaluated the efficiency of 70% alcohol for one minute, followed by sodium hypochlorite, with 1.0%, of active chlorine for five minutes, in the disinfestation of the explants, in addition to evaluating both the previous washing in a solution of ascorbic acid (250 mg L-1) and citric acid (150 mg L-1), as well as the addition of activated charcoal (2 g L-1), in the control of oxidation. There were four treatments with eight replicates of each. The second trial evaluated the effect of washing in a 40000 iu/L nystatin solution in the control of fungal contamination and the efficiency of disinfestation using 70% alcohol for one minute, followed by sodium hypochlorite with 1.0% of active chlorine for ten minutes. There were four treatments, with eight replications of each. The third trial evaluated the efficiency of sodium hypochlorite, with 1.0% or 1.5% active chlorine, alone or combined with Lysoform 40%, in addition to the use of Lysoform alone, in controlling contamination. There were 10 treatments with eight replications of each. The evaluations were made visually, after seven days. For the sealing and sterility test, the percentage of tubes with no apparent contamination was evaluated. In the in vitro disinfestation and establishment trials, the percentages of survival, oxidation and contamination were evaluated. The results showed that the Falcon tube showed greater efficiency in sealing the tubes and that the previous washing with citric and ascorbic acid solution reduced the oxidation levels. The levels of contamination remained high, indicating endogenous contamination and/or the need for phytosanitary treatment of the mother plant The present work serves as a basis for further studies on the in vitro establishment of the species.