In vitro regeneration systems for mutation breeding and genetic modification of azaleas

In vitro regeneration is an important breeding technique that can be used for mutation or genetic modification for azalea plants (Rhododendron subgenus Tsutsusi section Tsutsusi [Ericaceae]) with long breeding periods.
The in vitro reactions of leaf explants of several wild species and cultivars of azalea were assayed using the following two in vitro adventitious shoot regeneration protocols: a direct regeneration protocol without callus induction and a two-step protocol with callus induction.
In the direct regeneration protocol, Rhododendron × pulchrum (Sweet) ‘Sen-e-ōmurasaki’ (100%) and ‘Akebono’ (76.5%), showed a high rate of adventitious shoot regeneration from explant leaves. R. indicum (Sweet) ‘Hibai’ (39.1%), and R. viscosum (L.) Torr. (20%) also regenerated adventitious shoots, while the remaining azaleas failed to regenerate.
In the two-stage protocol, all azaleas formed callus from excised leaves, but only R. viscosum (69.2%) showed a high rate of adventitious shoot regeneration.
Rooting was induced in ‘Sen-e-ōmurasaki’, which showed the highest rate of adventitious shoot regeneration, by transplanting the explant leaves with adventitious shoots to sterilized potting soil.
Finally, all explants were successfully acclimatized.
These results offer a fundamental understanding of the in vitro regeneration system in azaleas.

V International Symposium on Woody Ornamentals of the Temperate Zone

A. Nakatsuka, K. Tasaki, N. Kobayashi

adventitious shoots, callus, direct regeneration protocol, Rhododendron indicum, R. × pulchrum, R. viscosum

https://doi.org/10.17660/ActaHortic.2025.1434.50