Cryopreservation of Populus trichocarpa and Salix dormant buds with recovery by grafting or direct rooting.

BACKGROUND Methods are needed for the conservation of clonally maintained trees of Populus and Salix. In this work, Populus trichocarpa and Salix genetic resources were cryopreserved using dormant scions as the source explant. OBJECTIVE We quantified the recovery of cryopreserved materials that originated from diverse field environments by using either direct sprouting or grafting. MATERIALS AND METHODS Scions (either at their original moisture content of 48 to 60% or dried to 30%) were slowly cooled to -35 degree C, transferred to the vapor phase of liquid nitrogen (LNV, -160 degree C), and warmed before determining survival. RESULTS Dormant buds from P. trichocarpa clones from Westport and Boardman, OR had regrowth levels between 42 and 100%. Direct rooting of cryopreserved P. trichocarpa was also possible. Ten of 11 cryopreserved Salix accessions, representing 10 different species, exhibited at least 40% bud growth and rooting after 6 weeks when a bottom-heated rooting system was implemented. CONCLUSION We demonstrate that dormant buds of P. trichocarpa and Salix accessions can be cryopreserved and successfully regenerated without the use of tissue culture.