Somatic embryogenesis and plantlet regeneration from cell suspension cultures of palmarosa grass (Cymbopogon martinii)

A cell suspension culture was established from nodal callus of Cymbopogon martinii (Roxb.) Wats in a liquid medium containing Murashige and Skoog (1962) basal salts, vitamins, 100 mg l-1 myo-inositol and 20 g l-1 of sucrose (MS) that was supplemented with 13.6μM 2,4-dichlorophenoxyacetic acid and 1.15 μM kinetin. An initial inoculum density of 2 x 104 cells ml-1 exhibited optimum cell growth. Calli were obtained 12-15 days after the suspension was plated onto semisolid medium of a similar composition. When calli were transferred to semisolid regeneration medium containing MS + 6.7 μM N6-benzyladenine + 1.15 μM kinetin, somatic embryogenesis and plantlet regeneration occurred after 10-25 days. There was no significant decrease in the regeneration potential of the calli even when the cultures were initiated from 47-week-old cell suspensions. Chromosome counts of cells in suspensions, calli and somatic embryos derived from cultures of different ages revealed the presence of diploids, tetraploids and octaploids. However, the 33 regenerated plants tested were all diploid, indicating that only diploid cells were capable of regeneration in vitro.