Micropropagation of Flame Azalea

Shoots tips excised from an actively growing stock plant of flame azalea [Rhododendron calendulaceum (Michx.) Torr.] were surface sterilized, the terminal portions were removed (decapitated) and the shoots placed horizontally on agar-solidified Woody Plant Medium (WPM) supplemented with 15 ppm 6-(γ, γ-dimethylallylamino)-purine (2iP). Within 4 to 6 months multiple shoot formation commenced. After 2 to 3 additional months of growth, axillary shoots were excised from the original explants. The shoots were decapitated and placed on WPM. After 2 subcultures, 8-node axillary shoots were excised, decapitated and cultured on agar-solidified WPM supplemented with 0, 4, 8, 12, 16, 24, and 32 ppm 2iP. The greatest number of shoots (microcuttings) ≥ 5 mm (0.2 in) were produced at 12 ppm 2iP. Microcuttings ≥ 10 mm (0.4 in) were rooted using ex vitro procedures. Enhancement of both axillary shoot multiplication and shoot length was achieved by addition to the medium of 80 ppm adenine sulfate and 200 ppm NaH2PO4.

Micropropagation of Rhododendron chapmanii

Shoot tips excised from Chapman's rhododendron (Rhododendron chapmanii A. Gray) were surface sterilized, the terminal portions were removed (decapitated) and the shoots placed in liquid Woody Plant Medium (WPM) supplemented with 8 μM (1.6 ppm) 6(γ, γ-dimethylallylamino)-purine (2iP). Within 2 to 3 months axillary shoots excised, decapitated and cultured on agarsolidified WPM supplemented with 49 μM (10 ppm) 2iP. Multiple shoot formation consisting of adventitious and axillary shoots was observed within 4 to 6 months. These shoots were transferred to WPM supplemented With 8 μM (1.6 ppm) 2iP and cultured under reduced light levels to stimulate shoot elongation. Shoots ≥ 10 mm (0.4 in.) were harvested (microcuttings) and rooted using non-in vitro procedures. Enhancement of axillary shoot multiplication was achieved by culturing decapitated axillary shoots under reduced light levels in a horizontal position on WPM supplemented WIth 8 μM (1.6 ppm) 2iP.