In vitro regeneration of chickpea (Cicer arietinum L.): Stimulation of direct organogenesis and somatic embryogenesis by thidiazuron

In vitro regeneration in chickpea (Cicer arietinum L.) was achieved by direct culture of mature seeds on Murashige and Skoog (MS) medium supplemented with either N-phenyl-N'(-1,2,3-thidiazol-5-yl) urea (thidiazuron, TDZ) or N6-benzylaminopurine (BAP). Multiple shoots formed de novo without an intermediary callus phase at the cotyledonary notch region of the seedlings within 2 to 3 weeks of culture initiation. TDZ was found to be more effective compared to BAP as an inductive signal of regeneration. The former induced multiple shoot formation at all the concentrations tested (1 µM to 100 µM), although, maximum morphogenic response was observed at 10 µM concentration. Addition of naphthaleneacetic acid (NAA) alone or in combination with BAP to the MS medium failed to invoke a similar response. When the TDZ supplemented medium was amended with L-proline, the resultant regenerants were mostly somatic embryos. Histological investigations confirmed the switch in the regeneration pathway from directly formed adventitious shoots to embryogenesis. For obtaining plantlets, adventitious shoots were rooted on MS medium supplemented with 2.5 µM NAA; somatic embryos were germinated and established on MS medium. Normal plants were regenerated from both adventitious shoots and somatic embryos and transferred to soil.