Effect of proline and thymine on the establishment of friable callus and cell suspension culture of Dalbergia sissoo from the nodal region of over twenty-year-old trees

Dalbergia sissoo is an economically important timber species present throughout the Indian subcontinent. Vegetative propagation is difficult for this species, and in this study, nodal explants from a mature twenty-six-year-old tree were used to induce friable callus. Murashige and Skoog (MS) medium was optimized for converting compact callus into friable callus by adding different concentrations and combinations of proline (10–30 µM) and thymine (50–150 µM). The callus induction frequency of 100% was observed in the nodal segments. The modified MS medium increased the callus fresh weight (294.53%) compared to the control. Protocol for initiating cell suspension culture was also developed, and the growth of cells was measured every third day based on fresh and dry weights. The maximum fresh weight of cells, 8.4 g/mL, was observed after the 30th day, while the maximum dry weight, 3.8 g/mL, was recorded after the 33rd day. The viability of cells was observed at over 70% throughout the culture period when estimated using a trypan blue assay. This study provides a robust protocol for developing friable callus and suspension culture from nodal explants of D. sissoo, which could be utilized further for metabolic studies.