Abstract: The effects of oxytetracycline on the morphology of the seedling with witches' broom and global DNA methylation level of Paulownia tomentosa × Paulownia fortunei were investigated.The results indicated that the infected seedlings by phytoplasma recovered to normal morphology of the healthy seedlings after being treated with more than 20 mg L^-1 oxytetracycline,and the pathogen could not be detected with PCR in the seedlings.The global DNA methylation level of diseased seedlings was lower than that of healthy one.The oxytetracycline treatment was able to increase the DNA methylation level,and the methylation level of the diseased seedlings increased with the dose of applied oxytetracycline.However the increased methylation of infected seedlings with oxytetracycline treatment could still not reach to level of healthy seedling(CK),even the seedlings treated with lethal oxytetracycline concentration.

Key words: Paulownia tomentosa×P.fortunei, witches' broom plantlet morphology, oxytetracycline, DNA methylation