Ex Vitro Rooting of American Chestnut Improves Acclimatization Survival and Plantlet Quality

Abstract

Tissue culture of plants has many applications, from producing genetically identical horticultural varieties, to production of secondary metabolites, to virus indexing, and most relevantly, developing novel traits by genetic transformation. Using Agrobacterium -mediated transformation on somatic embryos, blight-resistant American chestnuts [ Castanea dentata (Marsh.) Borkh.] have been developed as shoot cultures in plant tissue culture. Rooting tissue-cultured shoots and acclimatizing the rooted plantlets are key steps in tree production. In this study, in vitro and ex vitro rooting methods were compared. The ex vitro method resulted in a lower initial rooting percentage but an overall higher survival percentage, resulting in higher potted plant production. The higher survival was likely due to partial acclimatization taking place before the plantlets were transplanted into potting mix. After 8 weeks, plantlets rooted via the ex vitro method were taller, and had more, and larger, leaves than the in vitro -rooted plantlets. These trees are currently in high demand for inoculation studies for federal regulatory review and eventually for restoration of this keystone species to its native habitat.