Effect of chemical and physical factors in in vitro propagation and volatile fraction analysis of Aloysia triphylla (L'Herit) Britton

Abstract

Aloysia triphylla is a deciduous shrub, which has essential oil rich in citral. The objectives of this work were to study the influence of explant sources, basal nutrient media, explant orientation and nitrogen concentration on in vitro plantlet growth as well as on the volatile compounds of Aloysia triphylla. In the establishment phase different explant sources (1, 2, 3 and 4° nodal segment) and different media were tested. Nodal segments were obtained from mother plant to establish primary explants. Segments were washed in running tap water, surface-sterilized with ethanol followed by immersion in bleach solution and then rinsed five times in sterile distilled water. The explants were cut into segments of approximately 1.0 cm in length and inoculated on MS, B5 or WPM medium. After the establishment phase the influence of explant orientation on growth was evaluated and nodal segment with 1 or 2 buds were cultured on MS medium in vertical or horizontal position. Another experiment was done to evaluate the effect of nitrogen concentration. Nodal segments of 1.0 cm were cultured on MS with 15, 30, 60 or 120 mM of nitrogen. The 1 and 2° node were shown to be suitable for the establishment phase, independently from the medium. The number of shoots and dry biomass accumulation were higher when explants were horizontally cultured. The HS-GC-MS analysis of the volatile fraction of plantlets developed in MS medium detected the presence of 6-methyl-5-hepten-2-one in high amounts, while plantlets developed in WPM medium produced higher levels of citral. Increasing the levels of nitrogen in the medium led to a decrease in the yield of major volatile constituents.