S04 - Session O4 - Molecular insights to understand micropropagation - Influence of flavonoids and phenolic acids in the in vitro propagation of tamarillo

Authors: André Caeiro *, Jorge Canhoto, Sandra Correia

Tamarillo ( Solanum betaceum Cav.) is a Solanaceae tree indigenous to South America. Because of its agronomical importance and the problems associated with traditional propagation methods, several biotechnological processes have been employed to clone this plant. Previous studies have shown that the presence of certain secondary compounds in the culture medium, namely flavonoids and phenolic acids, influence the cellular response in terms of callus formation. As some of these compounds may be naturally produced by the plant, the objective of this work was to evaluate if exogenous concentrations influence in vitro plant growth. Phytomers from in vitro established clones were cultivated in jellified Murashige and Skoog medium supplemented with sucrose (8.6 mM) and 6-Benzylaminopurine (0.88 µM). To test the influence of secondary metabolites, either caffeic acid (896 µM), rutin (197.5 µM) or anthranilic acid (1.164 mM) were added to the medium. The initial shoot length was measured, and the shoots kept in a growth chamber for 7 to 8 weeks. After this period, growth rates were calculated as the final lengthninitial length/time of growth. Root development was observed, as well as the length of the longest root and number of leaves produced. Results show anthranilic and caffeic acid as severe inhibitors of plant growth and adventitious root formation, with growth rates close to 0 and no rooting observed in the presence of anthranilic acid. Roots grew from basal callus that likely developed because of the presence of 6-Benzylaminopurine. Assays are underway to determine the influence of this hormone in rooting process. Rutin grown plants show higher growth rates and number of leaves when compared to control (0.6473 +- 0.1703 cm/week and 9 +- 3 per plant, respectively). However, the presence of this compound decreases the rooting success (52 % of rooted explants) whereas the root length appears to be unaffected.