In Vitro Callus Induction and Regeneration of Gleditsia caspica Desf

Gleditschia  caspica Desf is one of the one of the tree species of the Hyrcanian forests. Extreme grazing, overexploitation of livestock, and the lack of natural regeneration system in diverse ecosystems have put Gleditsia caspica in danger of extinction. In this study, the conditions of the callus induction and regeneration were investigated under different growth regulators treatments. For this purpose, Stem, hypocotyl and root specimens were cut from sterile intact seedlings and considered as a separate explant. The MS medium supplemented with IBA, NAA and 2,4-D at different concentrated levels (0.5, 1.5, 3 and 4 mg / l) and TDZ, 2ip, BAP and Kin at different concentrations (0.1, 0.5 and 1 mg/l) were used for callus induction. Growth regulators of TDZ and 2,4-D on 0.5, 1 and 2 mg/l concentration in MS medium were used to regeneration. Regarding rooting, callus-derived plantlets exposed to 5 µM IBA in MS media. The characteristics of callus percentage, fresh and dry weight, callus area, color, type and growth curve of calluses were compared. Also, the proliferation percentage and mean number of shoots in each explant were examined. The results showed that the effect of explants and hormone type on the callus induction percentage showed a significant difference at the level of 99%. The percentage of callus induction in the stem explants were much higher than that of the hypocotyl and roots. The effect of different hormones on all stem explant characteristics was significantly different at 99%. The results showed that the 2,4-D yielded the highest and IBA resulted to the lowest percentage of callus induction among the studied auxins. Among the cytokines, Kin had the lowest and TDZ leads to the highest percentage of callus induction. The growth curve of fresh and dry weight in regenerated calli indicated the privilege of 2,4-D compared to other hormones(P<0.05). In general, according to the obtained results, it is recommended to use MS + 0.5 mg/l 2.4-D + 0.5 mg/l TDZ formula for indirect regeneration of Gleditschia  caspica.