Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: May 26, 2011
Publication Date: N/A
Technical Abstract: The USDA-ARS, National Plant Germplasm System (NPGS), preserves 20 different Juglans species with over 680 different accessions that are maintained as field plantings. Cryopreservation of these genetic resources is an economic alternative to a costly back-up planting in another location. One of the major obstacles to using cryopreservation for Juglans germplasm is the lack of reliable cryo-processing protocols that result in sufficient post-cryo viability of the material. We used dormant winter buds of butternut (J. cinerea), black walnut (J. nigra) and Persian walnut (J. regia) to test the suitability of the cryopreservation method used for apple dormant buds to cryopreserve germplasm of these nut trees. That method uses dormant buds from twigs cut into one node segments, desiccated to 25-30% moisture content, slow cooled to -30oC and exposed to liquid nitrogen vapors (LNV) for at least 24 hours. The viability is tested by grafting the LNV exposed buds onto rootstocks. Modifications to the apple dormant bud cryopreservation method included twig cold-hardening under two different light regimes, soaking in ABA or sucrose solutions (2oC, 4 days) prior to desiccation and post-cryo viability testing by forcing shoot growth under mist instead of grafting. Post-cryo viability evaluated under misting conditions was between 60–100% for black walnut and 10-60% for Persian walnut whereas the survival of controls (one-node segments stored at -5oC) was 62.5-100% and 80-100% respectively. Cryo-survival was also genotype dependent. These data suggest that cryopreservation of Juglans germplasm using dormant winter buds may be an applicable method for backing up of nut-tree collections. Refinement of pretreatment conditions especially for Persian walnut accessions, may result in higher viability.