Abstract:

Measures to promote rooting of in vitro shoots were conducted with six precocious walnut cultivars which had been subcultured for 4 years. It was found that successful rooting was closely related to inducing method, duration of IBA treatments, IBA concentrations, light conditions, and developing state of the shoots. The rooting rates of 60.5%～89.7% and 2.0～3.6 roots per shoot were achieved in six cultivars by adopting tender shoot with smaller leaves and longer internodes and using the two steps method that was firstly induced on 1/4 DKW medium with IBA between 5.0 to 10.0 mg·L^-1 for 10～15 days under dark condition, then transferred to the DKW medium without IBA under light. Meanwhile, changes of IAA and ABA level in shoots were monitored during rooting inducing. The regulations and control of hormones during walnut shoot rooting was discussed in this paper. The rooted shoots have been successfully transplanted to field.

Key words: Juglans regia L. cultivar, Shoot in vitro, Root promoting, Shoot developmental state, Endogenous hormone