Abstract:On a series of Murashige and Tucker (MT) media supplemented with different growth regulators, the 8-week-old unfertilized ovules of Washington navel orange (Citrus sinensis) were able to regenerate perfect plantlets via somatic embryogenesis or organogenesis. The sorts and combinations of exogenous hormones had remarkable effects on the induction, growth and differentiation of its callus. It was found that the most suitable induction medium was MT medium supplemented with 1.0 mg/l BA and 0.5mg/l 1AA. The most suitable differentiation medium was MT medium supplemented with 1.0 mg/l IBA. It was proved by indicator plant examination that the nucellar plantlets free of citrus exocortis virus (CEV) and citrus tristeza virus (CTV) had been obtained from infected trees.