The genus Rhododendron L. includes many popular gardening species of azalea widely
used in landscaping, which illustrates their great commercial value. Their large-scale production
can be achieved by in vitro propagation, and such techniques can also be used as a protocol
to recover certain endangered Rhododendron species. However, frequent subculturing for longterm
maintenance of tissue-cultured materials may lead to a risk of somaclonal variations and
contamination. Therefore, the present study was conducted to develop a slow-growth storage
method to reduce the growth of explants, thus prolonging the interval between subcultures.
Based on a proliferation medium for the micropropagation of R. simsii Planch., sucrose was
replaced by mannitol and sorbitol or in combination with sucrose in different concentrations as
the osmoticum. Three storage temperatures (4, 10, and 22℃) were synchronously investigated
to conserve the in vitro shoots of R. simsii in the dark. An optimal storage protocol was thus
determined based on the shoot survival rate and recovery growth from storage. The removal of
cytokinin from the storage medium and manipulating the illumination condition were further
investigated. After 8 mo of storage in a medium containing 3%(w v-1) sucrose, 33.6 μM 6-(γ-γ-
dimethylallylamino) purine (2iP) at 22℃/illumination, the shoots of R. simsii still maintained
their recovery growth with no subculturing. The explant rooting capability and subsequent acclimatization
were both unaffected.