Evaluation of different antioxidants during in vitro establishment of allspice (Pimenta dioica L. Merrill): a recalcitrant species

Abstract

Background: Pimenta dioica L. Merrill is a tree whose fruits are used as a spice due to their culinary and therapeutic uses. Conventional propagation techniques using seeds and cuttings do not guarantee the phytosanitary quality of this crop. Therefore, the use of Plant Tissue Culture techniques are an option for in vitro establishment. The aim of this study was to evaluate the effect of different antioxidant agents (Methylene blue, L-cysteine and silver nanoparticles) added to MS (Murashige and Skoog) culture medium at different concentrations (0, 50, 100 and 200 mg L-1) during axenic establishment of buds used as explants of P. dioica. Results: The percentage of survival, oxidation and contamination was determined, as well as the content of soluble phenols, cell wall-linked phenols, antioxidant capacity and lipid peroxidation. Results showed significant differences among the different antioxidants for the evaluated variables; the highest survival occurred in the treatments with the addition of L-cysteine with percentages greater than 40 %, while the lowest survival occurred in the control treatment, 100 and 200 mg L-1 methylene blue, with 0, 3.3 and 0% survival, respectively. The highest percentage of oxidation was observed in the control treatments, 100 and 200 mg L-1 methylene blue with 96.67% oxidation, while the lowest percentages were observed in explants treated with L-cysteine, with 30% oxidation. Treatments with 100 and 200 mg L-1 AgNPs had the lowest contamination values, with 20%. Biochemical determinations showed that L-cysteine and 50 and 100 mgL-1 AgNPs resulted in an increase in the content of soluble phenols. The highest contents of cell wall-linked phenols were obtained in treatments with 200 mg L-1 methylene blue, L-cysteine, and 200 mg L-1 AgNPs. Analysis of antioxidant capacity revealed that all treatments had a reaction of scavenging / reduction mechanisms free radicals. Regarding lipid peroxidation, the highest content of malondialdehydes was observed in the control treatment and 200 mgL-1 methylene blue. Conclusion: the addition of L-cysteine to the culture medium showed a higher survival rate, decreased oxidation, greater production of phenolic compounds, increased antioxidant capacity and decreased lipid peroxidation, this amino acid being an alternative to reduce oxidation during in vitro introduction of allspice and other species that exhibit recalcitrance in vitro during establishment.