Evaluation of three disinfection protocols and three protocols for the use of anti-oxidants in in vitro cultivation of cherimoya (Annona cherimoia mill.) and the quantitative determination of branch phenolic content

In vitro propagation of cherimoya presents several problems, the most important among them being the high contamination rate when field material is used and the material's strong oxidative capacity due to the high content of phenolic compounds. Two trials were carried out to evaluate protocols for the disinfecting nodal sections of adult cherimoya material and to evaluate protocols for the use of anti-oxidants in culture medium of meristematic apexes to avoid oxidation losses during establishment. A third trial was carried out to determine the period with the lowest phenolic content. Monthly determinations were made of phenolic concentrations in the apical, medium and basal parts of branches by the method of Swain et al. (1959), relating phenolic contents to fresh weight. The branches were herbaceous, semi-woody or woody, depending on phenological stage and/or the time of the year at which they were collected. The first trial, carried out monthly from June to January, did not show any effect of disinfectant or of the part of the branch used (apical, medium or basal). On the contrary, there was a phenological (seasonal) effect. For phenological reasons, the second trial was only carried out in January. No positive effect was obtained with either of the evaluated oxidants (PVP-6755, ascorbic acid + citric acid, and DIECA). The results obtained in the third trial showed that the lowest phenolic levels for all branch sections are found in June, whereas the highest occur in August and September when vegetative growth of cherimoya decreases and lignification increases.