Rooting and shooting: dual function of thidiazuron in in vitro regeneration of soybean (<Emphasis Type="Italic">Glycine max.</Emphasis> L)

Thidiazuron (TDZ), primarily a cotton defoliant, has been later accepted as a plant growth regulator. In spite of extensive studies, the physiological function of TDZ is still uncertain. The aim of the present experiment was to study the activity of TDZ in in vitro regeneration of soybean. The seeds of soybean were cultured separately on MS and B5 medium supplemented with TDZ. The hypocotyls, cotyledons, cotyledonary nodes without axillary buds and cotyledonary nodes with axillary buds were used as explants and their capacity to direct regeneration was tested on both MS and B5 media containing TDZ (0.9–5.4 μM). Shoot formation was observed only on cotyledonary nodes with axillary buds cultured on MS and B5 basal media with TDZ (0.9–5.4 μM). All tested explants cultured on B5 medium with TDZ produced roots. Root formation was not observed on MS basal media supplemented with TDZ. Results show that TDZ functions as cytokinin (to produce the shoots) and auxin (to produce the roots) on various explants depending on the basal medium used.