Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 4/1/2009
Publication Date: 4/20/2009
Citation: Ellis, D.D., Ostry, M., Moore, M., Ambruzs, B.D., Jenderek, M.M. Cryopreservation of Juglans cinerea (butternut) dormant buds. I International Symposium on Cryopreservation of Horticultural Species, April 5-8, 2009, Leuven, Belgium. pp. 78. Meeting abstract.
Interpretive Summary: Butternut (Jungians cinerea) is a deciduous tree native to the eastern US and southeastern Canada. The nuts called lemon nuts are valued due to thier oily texture and pleasant flavor. The wood is softer than black walnut making it a favorite of woodcarvers. Butternut is threatened by an introduced fungus that causes a lethal canker disease that has killed 90% of the trees in some native populations. Preservation efforts for the tree include setting up field plantations from cuttings of trees with putative canker resistance yet the disease is wide spread and the fungus can be found in many of these orchards. One method for long-term preservation of woody species is the cryopreservation of dormant buds in liquid nitrogen (-320oF), although this has been developed and shown to be successful for a very few species. This report outlines the development over a three-year period of a system for the cryopreservation of butternut dormant buds. Five different clones of butternut were tested and survival of buds after cryopreservation ranged from 20-53% depending on the clone. Grafting of single butternut dormant buds is difficult yet this study clearly showed that plants can be obtained from preserved material. We hope to expand the butternut cryopreservation program in the future to include more clones.
Technical Abstract: Juglans cinerea (butternut) is a deciduous tree native to the United States and Canada with oblong-lemon shaped nuts with oily texture and pleasant flavor. Butternut wood is softer than wood of the black walnut making it a favorite wood for woodcarvers. In North America butternut is seriously threatened by a canker disease caused by the introduced fungus (Sirococcus clavigignenti-juglandacearum) which has killed 90% of the native butternut in some areas. While not listed as threatened or endangered yet in the US, it is listed as endangered in Canada. The USDA-Agricultural Research Service (ARS) National Plant Germplasm System maintains a germplasm collection of 26 selected accessions while the USDA-Forest Service (FS) maintains numerous field sites of selected accessions varying in canker resistance. Due to the threat of the canker disease all these plantings, like the wild populations, could become threatened. The development of a cryopreservation protocol for dormant buds of butternut has been successful and serves as a good model for the potential development of protocols for dormant bud cryopreservation of other woody plants. In 2006, a feasibility study was done on the cryopreservation of dormant butternut buds utilizing a protocol used for the cryopreservation of dormant apple buds as a starting point. Five accessions were tested and despite the use of subpar rootstock left over from other studies and limited replications for each treatment, (we also did not rehydrate buds that year) four of the accessions had at least one out of ten buds survive cryopreservation. The first year further defined that survival after slow cooling to -35oC was greater when buds were dehydrated to 25-30%MC vs. 30-35%MC. Based on this meagre success in the first year, in 2007 the focus was to increase sample sizes and survival rates by using more buds and first grade root stock. Utilizing the same five accessions, survival of buds after cryopreservation increased to 53% in one accession (survival for all five accession ranged from 13% to 53%). Results from a third year (2008), confirmed the possibility of using the apple dormant bud cryopreservation system to butternut preservation in that success rates were comparable to those obtained in 2007 (the survival after LN2 ranged from 20% to 53% in 2008). Chip grafting in butternut is difficult with few researchers having high levels of survival and is therefore could be a limitation in cryopreservation of butternut. However, as evidenced from these studies, the species is amenable to cryopreservation of dormant buds. Future work will focus on cryopreservation of both the ARS and the FS butternut collections.