The effect of different concentrations of TDZ and BA on in vitro regeneration of Iranian cannabis (Cannabis sativa) using cotyledon and epicotyl explants

The present study was carried out to investigate micropropagation possibility and determine the optimal medium composition and plant growth regulators (PGRs) combinations under in vitro conditions. The cotyledon and epicotyl explants obtained from 1 month old in vitro grown seedlings were used in MS medium containing BA (0.1, 0.2, 0.5, 1, 2 and 3 mg-1) and TDZ (0.1, 0.2, 0.5, 1, 2 and 3 mg-1) either alone or in combination with 0.5 mg-1 IBA. The response of cannabis explants to PGRs treatments was much different from those observed in most of plant species. That is, callus formation had priority over direct regeneration in most of the PGRs treatments. Comparing the two explants, cotyledon had higher callus formation frequency and the largest callus volume was obtained for this explant in MS medium supplemented with 3 mg-1 TDZ + 0.5 mg-1 IBA. The highest callus fresh weight (3.15 gr) was obtained for cotyledon explant treated with 2 mg-1 TDZ+ 0.5 mg-1 IBA. In shoot formation step, the highest rate of shoot regeneration was achieved in the calli produced from epicotyl explant treated with 2 mg-1 BA + 0.5 mg-1 IBA; and the highest length of regenerated shoots (1.23 cm) was observed in 2 mg-1 BA + 0.5 mg-1 IBA treatment. In general, cotyledon was the best explant and TDZ in combination with IBA was the best treatment for callus formation. Epicotyl explant also showed better regeneration compared to cotyledon.