Abstract
An efficient protocol for the in vitro germination and propagation of Larrea divaricata CAV. (Jarilla) was established. To determine the effect of different growth regulators on the growth rates and phenol production, apical-node microshoots from in vitro germinated plantlets were incubated on the following media: 1) full-strength MS (Murashige and Skoog) salt medium with different ratios of α-naphthaleneacetic acid (NAA) and N6-benzyladenine (BA); 2) after pre-treatment with indolebutyric acid (IBA), transfer to MS medium of different inorganic salt strengths; and 3) full-strength MS salt medium with different ratios of sucrose and IBA. Successful microshoot rooting percentages were achieved by the second and third strategies, the highest being 87.5—100%. The maximum principal shoot length and node number obtained by the second strategy corresponded to the plantlets previously induced with 50 μM IBA, and grown on half- or full-strength MS salt media (7.03±0.93 and 9.86±1.07 cm, respectively) while in the third strategy the most efficient micropropagation medium was full-strength MS salt medium supplemented with 7.5 μM IBA: 3% (w/v) sucrose (7.05±1.08 and 7.0±1.51 cm, respectively). The phenol concentration was determined by analytical HPLC. The highest content of nordihydroguiaretic acid (NDGA) accumulated in microplants of L. divaricata cultivated on half-strength MS salt medium (35.90±3.82 mg/g DW). Reducing the MS medium salt concentration by half, in the absence of IBA, it resulted in a higher NDGA production. NDGA production was not sensitive to the variation of IBA concentration. The medium supplemented with 5% (w/v) sucrose and 2.5 μM IBA induced not only a higher NDGA production but also a higher quercetin production.
