ARS | Publication request: Cryopreservation Of Dormant Buds From Diverse Fraxinus Species

Submitted to: CryoLetters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 25, 2009
Publication Date: April 19, 2009
Citation: Volk, G.M., Bonnart, R.M., Waddell, J.W., Widrlechner, M.P. 2009. Cryopreservation Of Dormant Buds From Diverse Fraxinus Species. CryoLetters. 30:262-267.

Interpretive Summary: Ash (Fraxinus) is an economically important tree genus in the landscape industry, as well as a key component of North American forests, especially in the North Central United States and adjacent regions in Canada. In recent years, the Emerald Ash Borer beetle (Agrilus planipennis) has significantly threatened the survival of native North American Fraxinus species. Ash seeds can be conserved, but the trees resulting from ash seeds are not genetically identical to the parent trees. We have developed a method to conserve genetic clones of ash trees by collecting vegetative buds mid-winter from either male or female trees. Stem sections containing vegetative buds are then dried to a moisture content of 30% (weight/volume), slowly cooled to -30oC or -35 oC, and then plunged into liquid nitrogen vapor for long term storage. For recovery, buds are rehydrated and grafted on to rootstocks. Recovery percentages ranged from 34 to 100% after LNV exposure and were dependent upon accession and cooling rate. The proposed cryopreservation methods can compliment seed-collection efforts aimed at conserving diversity, supplementing ex situ genebank and botanic-garden collections.

Technical Abstract: Ash (Fraxinus) is an economically important tree genus in the landscape industry, as well as a key component of North American forests, especially in the North Central United States and adjacent regions in Canada. In recent years, the Emerald Ash Borer beetle (Agrilus planipennis) has significantly threatened the survival of native North American Fraxinus species. A dormant-bud cryopreservation technique has been developed as a method to conserve specific clones of ash. Dormant buds were successfully cryopreserved when desiccated on their stem sections to 30% moisture content (w/v) and then cooled at rates of either -1ºC/h or -5ºC/day to either -30 or -35ºC before immersion in liquid nitrogen vapor (LNV). Stem sections were removed from LNV, warmed, and rehydrated, and their buds grafted onto rootstocks to evaluate survival. Recovery percentages ranged from 34 to 100% after LNV exposure and were dependent upon accession and cooling rate. The cryopreservation methods proposed herein can compliment seed-collection efforts aimed at conserving diversity, supplementing ex situ genebank and botanic-garden collections.