Adventitious shoot formation from leaf explants of Rhododendron
A protocol for high frequency adventitious shoot regeneration adventitious shoot regeneration from leaf explants of Rhododendron spp. has been developed. The highest percentage of regeneration and the greatest number of shoots were obtained when leaf explants were cultured on Anderson's medium containing 4.9 μM IBA and 73.8 μM 2iP. Genotypic variation was observed for adventitious shoot regeneration potential among the seven cultivars tested. Regeneration frequencies ranged from 0 to 96%. ‘Lodestar’ had the highest rate of regeneration after 3 months of culture with 96% shoot regeneration and an average of 14 shoots per explant. Regenerated shoots were rooted in soil in about 2 months. This protocol should be useful in applying gene transfer techniques to Rhododendron improvement.
Adventitious Shoot Regeneration from in Vitro Subcultured Callus of Rhododendron Exbury Hybrids

Callus culture establishment and adventitious shoot development from callus of Rhododendron × ‘Gibraltar’ (G) and R. × ‘Old Gold’ (OG) after serial subculture were determined. Callus grew on Anderson's Rhododendron medium containing 2,4- D at 0.0045, 0.009, or 0.018 mm, but was optimum at 0.018 mm, since shoot organogenesis was suppressed at that level. After two callus subcultures, adventitious shoot development from callus on media containing 0, 0.017, 0.034, 0.068, or 0.136 mm zeatin (mixed isomers) was optimum at 0.034 and 0.068 mm zeatin for G and OG, respectively. After 17 weeks (five subcultures), 70- to 75-mg pieces of G and OG callus regenerated ≈20 shoots each. Adventitious shoot regeneration from callus declined with prolonged callus subculture. Regenerated plants are currently being evaluated for somaclonal variation. Chemical names used: (2,4-dichlorophenoxy)acetic acid (2,4-D); (E)-2-methyl-4-(1H-purin-6-ylamino)-2-buren-1-ol (zeatin).
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 th...