Shoot Regeneration from Rhododendron Leaf Explants and Callus

Abstract

Shoots were regenerated adventitiously from leaf explants and from callus to determine if there is any effect on somaclonal variation and tissue proliferation of the three rhododendron cultivars, Arctic Pearl, P.J.M. Elite, and Purple Gem. The focus of this paper is regeneration. Leaves from shoot cultures were placed on a pre-conditioning medium for 2 weeks containing 10 μM indolebutyric acid (IBA) and 50 μM isopentenyladenine (2iP) and then transferred to treatment media. The six media tested were 0.1, 1.0, or 10.0 μM thidiazuron (TDZ) or 25.0, 50.0, or 75.0 μM 2iP. All treatment media contained 10 μM IBA. Data were collected on shoot regeneration after 24 weeks. Shoot number increased with increasing levels of TDZ for `P.J.M. Elite', but decreased with increasing concentrations of TDZ for `Arctic Pearl'. Shoot number for `Purple Gem' leaf explants was greatest when there was 1.0 μM TDZ in the medium. In another experiment, leaf explants were placed on the same preconditioning medium for 2 weeks as above and then transferred to three treatment media containing 0.1, 1.0, or 10.0 μM TDZ and 100 μM IBA. Callus was produced on leaf explants after 4 weeks, regardless of cultivar or level of TDZ. After 11 weeks, adventitious shoots regenerated from `Purple Gem' callus regardless of level of TDZ and from `Arctic Pearl' callus when the medium contained 0.1 or 10.0 μM TDZ. After 11 weeks, there were no visible shoots on `P.J.M. Elite' callus.