Elimination of ‘Candidatus Phytoplasma aurantifolia’ from Chrysamthemum morifolium cv. Ajay Orange by application of oxytetracycline by in vivo and in vitro treatments

Abstract

Chrysanthemum morifolium is severely affected by a phytoplasma disease which causes significant loss in market quality of the flowers. So far, no real control strategy is available to manage phytoplasma diseases in chrysanthemum. An attempt was made in the present study to obtain phytoplasma free C. morifolium cv. Ajay Orange plants by employing different concentrations of oxytetracycline treatments both in vivo and in vitro. Chrysanthemum plants showing little leaf, virescence and phyllody symptoms infected with ‘Candidatus Phytoplasma australasia’ (16SrII-D) were selected as the source plant. The chrysanthemum cuttings from six months old mother plants were treated with different concentrations of oxytetracycline for in vivo screening with two sets of experiments. In the dip method, the cuttings were dipped in different concentrations of oxytetracycline treatments for 16 hours. The foliar spray method was carried out with different concentrations of oxytetracycline on plants raised from the infected cuttings. In the in vitro method nodal segments maintained on MS medium, were transferred to media with the different concentrations of oxytetracycline. The oxytetracycline concentration of 80 mg/l was found optimal for the foliar spray in in vivo method with phytoplasma elimination of 80%, whereas in the dip method, both 80 and 100 mg/l were found to be optimal for phytoplasma elimination of 80 and 100%, respectively. The results of in vitro oxytetracycline treated plants showed 91.3% elimination at 80 mg/l of oxytetracycline concentration. Phytoplasma absence was confirmed by nested polymerase chain reaction analysis in all the treated plants in vivo and in vitro at a monthly interval up to three months. The result of the present study revealed that in vitro method of using oxytetracycline at 80 mg/l was the most efficient in elimination of phytoplasmas from infected C. morifolium plants.