Abstract

This study aimed to investigate the effects of various growth media and three types of auxins on glucosinolate biosynthesis in hairy root cultures of kale. Four different glucosinolates (4-hydroxyglucobrassicin, glucobrassicin, 4-methoxyglucobrassicin, and neoglucobrassicin) were used in this study. The accumulation of glucosinolates was influenced by both media and auxin treatments. Of the media treatments, full-strength Gamborg’s B5 medium (B5) supported the highest accumulation of total glucosinolates, followed by full-strength Murashige–Skoog medium (MS), whereas the lowest glucosinolates accumulation was in the half-strength MS medium treatment. The accumulation of glucobrassicin was very high, followed by 4-methoxyglucobrassicin, irrespective of the growth medium used. The highest content of glucobrassicin was measured in cultures in B5 medium, while MS medium resulted in the highest accumulation of 4-methoxyglucobrassicin. Half-strength B5 medium resulted in the highest content of neoglucobrassicin, and Schenk and Hildebrandt medium (SH) supported the highest content of 4-hydroxyglucobrassicin. The total and individual levels of glucosinolates in hairy root cultures of kale were all influenced by exposure to the nine auxin treatments, with the exception glucobrassicin. In general, levels of glucosinolate decreased with increasing concentrations of auxins. Treatment with the auxin indole-3-butyric acid (IBA) 0.1 resulted in the highest total concentration of glucosinolates, measuring 1.83 times higher than that of hairy root cultures treated with naphthalene acetic acid (NAA) 1.0, which resulted in the lowest glucosinolate concentrations. Of the four glucosinolates, glucobrassicin and 4-methoxyglucobrassicin contents were considerably higher. The auxin IBA 0.1 promoted the highest 4-methoxyglucobrassicin accumulation in the hairy root cultures of kale. The auxin treatment indole-3-acetic acid (IAA) 0.1 resulted in the highest amount of 4-hydroxyglucobrassicin and neoglucobrassicin. Hairy root cultures could be a valuable alternative approach for the production of glucosinolate compounds from kale.

Key words: Glucosinolates, growth media, auxin, hairy root, kale