Estabelecimento in vitro de Annona crassiflora e Annona squamosa utilizando segmentos nodais

Abstract

The species of the Annonaceae family can be propagated by seeds and vegetative methods. However, most species of this family shows inhibition of germination, dormancy imposed by the result of the presence of inhibitors, which slow the germination process, which usually happens irregularly precluding the production of seedlings evenly. An alternative to its spread is the asexual reproduction via cloning or in vitro micropropagation. This study aimed to establish a protocol for disinfection and in vitro establishment of shoot explants of two species of Annonaceae (Annona crassiflora Mart. and Annona squamosa L.) using micropropagation as a new alternative for the production of seedlings. The plant material was obtained from young vegetative branches collected from plants found in Cerrado region of cities Campo Grande and Dourados, Mato Grosso do Sul. To achieve the proposed objectives five separate experiments were performed with both species. Experiment 1: Effect of time of exposure ( 10, 15 and 20 minutes ) and disinfest (calcium hypochlorite and sodium hypochlorite at 2.5 %) in vitro establishment of Annona crassiflora; Experiment 2: Effect of the type of medium culture (WPM and MS) and growth pH ( 5.2, 5.4 and 5.8 ) in vitro establishment of Annona crassiflora; Experiment 3: Effect of exposure time ( 10, 15 and 20 minutes ) and disinfest (calcium hypochlorite, sodium hypochlorite and 2.5 %) in vitro Annona squamosal establishment; Experiment 4: Effect of different concentrations treatment with mercuric chloride (0.0 - control; 0.025, 0.050, 0.075 and 0.100 %) in vitro establishment of Annona squamosa; Experiment 5: Effect of different concentrations of hydrogen peroxide (10, 20,30 and 40 %) is added to sodium hypochlorite (2.5 %) in the disinfestation of explants in vitro establishment Annona squamosa. The evaluations were performed at 7, 14 and 28 and or 56 days, with the final evaluation computed as before. The variables analyzed were: percentage of bacterial contamination, percentage of fungal contamination, percentage of oxidized explants and percentage of explants in vitro established (considering its those issued shoots). From the results obtained it is concluded that during the initial in vitro A.crassiflora, the sodium hypochlorite has greater efficiency in the control of bacterial contamination while for the same variable, 15 minutes of exposure to the agent reduces disinfest at approximately 50% explant, regardless of the type of hypochlorite (calcium or sodium). The explants cultured on WPM medium with pH 5.8 have a lower percentage of fungal contamination. With pH 5.8, the culture medium MS causes less oxidation of explants. But with pH 5.4, the WPM is more effective in controlling this variable. To establishing in vitro A. squamosa it was concluded that the longer the duration of exposure to sodium hypochlorite, more low the fungal contamination. The reverse is observed on the disinfection with calcium hypochlorite. These same treatments were not effective in controlling bacterial contamination and did not influence the oxidation of explants. Treatment with mercuric chloride at concentrations 0.075 %, there is a reduction of bacterial contamination, however, none of the concentrations was effective in controlling fungal contamination. The addition of hydrogen peroxide to sodium hypochlorite, as well as the control treatment only with sodium hypochlorite at all concentrations tested allowed to obtain a large number of established explants (25%). However, the data obtained in other variables fungal contamination and bacterial oxidation did not differ between treatments.