Mannitol-induced drought stress on calli of Trigonella foenum-graecum L. Var. RMt-303.

Different explants of fenugreek, T. foenum-graecum L. (Var. RMt-303), were compared for their callus induction and subsequent shoot regeneration capabilities on Murashige and Skoog media supplemented with different phytohormones in varying concentration. The highest percentage of callus induction frequency was observed in 1ppm benzylaminopurine (BAP). Maximum shoots were induced on media supplemented with 0.5ppm BAP using leaf and stem tissues as explants. However, root tissues showed only callusing with no subsequent shooting. Cotyledonary node responded better than hypocotyls in terms of shoot induction on media supplemented with thidiazuron (0.1ppm). The callus was subjected to drought stress as simulated by reduced water potential of growth media due to addition of mannitol. Calli could withstand -2 MPa water potential till 30 days indicating that the drought stress tolerance mechanisms are functional in this variety. Chlorophyll a and b and total chlorophyll, proline and total phenolic contents, total peroxidase and catalase activities increased under stress conditions suggesting the tolerance of callus to drought stress. However, ascorbate peroxidase, guaiacol peroxidase activities were found to decrease slightly. Malondialdehyde and H2O2 contents were found to decrease while only a slight disturbance was found in membrane stability index. These results underline the mechanisms that are crucial for drought stress tolerance in fenugreek.