Production of phytoplasma-free plants from yellow leaf diseased Catharanthus roseus L. (G.) Don

摘要

Catharanthus roseus L. (G.) Don., an important medicinal plant, is a susceptible host of phytoplasma. An attempt was made to obtain phytoplasma-free plants employing in vitro chemotherapy. Plants showing reduction in the size of leaves with pale-greenor yellow colour and virescence of flowers were the source of tissue culture experiment. Shoot tips excised from phytoplasma-infected plants grew optimally in Murashige and Skoog's (MS) medium supplemented with kinetin (2.0 mgl~(-1)), 6-benzylaminopurine CO.75 mgl~(-1)) andindole-3-butyricacid (0.1 mg 1~(-1)). Phytoplasma-infected shoot-tip explants, maintained on MS medium, were subjected to different concentration of oxytetracycline (25-100 mg 1~(-1)) for 2 weeks and then transferred to antibiotic-free medium for six subsequent serial transfers. Established shoot cultures, with newly emerged shoots showing no phytoplasma symptoms were selected and subcultured for the induction of roots. An oxytetracycline concentration of 75 mg 1~(-1) was optimal for freeing phytoplasma from the infected tissues. About 50% of regenerated plants were phytoplasma free as confirmed by polymerase chain reaction, and they remained healthy for more than 3 years.