Conservation of the USDA-ARS National Plant Germplasm System Apple Collection using dormant bud cryopreservation

Authors: Volk, Gayle; Jenderek, Maria; Chao, Chihcheng

Submitted to: Eucarpia Fruit Breeding Symposium
Publication Type: Abstract Only
Publication Acceptance Date: 6/1/2015
Publication Date: 6/15/2015
Citation: Volk, G.M., Jenderek, M.M., Chao, C.T. 2015. Conservation of the USDA-ARS National Plant Germplasm System Apple Collection using dormant bud cryopreservation [abstract]. XIV Eucarpia Fruit Breeding and Genetics Symposium. Available: http://www.eucarpiafruit2015.org/wp-content/uploads/2014/06/03-poster-list.pdf.

Interpretive Summary: The USDA-ARS National Plant Germplasm System maintains a grafted collection of apple accessions representing 49 taxa in Geneva, NY. Since 1993, dormant buds of many of these accessions have been routinely cryopreserved at the USDA-ARS National Center for Genetic Resources Preservation (NCGRP) in Fort Collins, CO. In the standard procedure, dormant buds are sent to NCGRP in mid-winter. Scions are cut into 35 mm bud sections and desiccated at -5 degrees Celsius to a moisture content of 25 to 30% (fresh weight basis). Desiccated single-bud sections are sealed into polyolefin tubes, slow cooled at -1 degrees Celsius per hour to -30 degrees Celsius, held at -30 degrees Celsius for 24 hours, and then placed into the vapor phase of liquid nitrogen (LNV) for long term storage. For viability testing, one tube containing 10 dormant buds is rehydrated at 2 degrees Celsius in moist, sterile peat moss and then grafted onto rootstocks. In the 1990s, it was standard to process 60 dormant buds per accession and to use 12 of those buds to assess viability during the same season. This left a maximum of 48 buds in LNV per accession. In this analysis, successfully cryopreserved accessions were defined as those that have 40% viability and 19 or more predicted viable buds remaining in LNV. Of the 2302 accessions currently cryopreserved at NCGRP, 2023 accessions meet these requirements. An additional 31 accessions have at least 19 predicted viable buds in LNV, but have lower than 40% viability. Criteria were established to prioritize the 568 apple accessions that are either inadequately backed up at NCGRP or have not yet been processed. These criteria include the likelihood of success in cryopreserving the Malus taxon, the vulnerability of the field trees, the number of viable buds currently stored in LNV, and previous failures in response to the standard procedure.

Technical Abstract: The USDA-ARS National Plant Germplasm System maintains a grafted collection of apple accessions representing 49 taxa in Geneva, NY. Since 1993, dormant buds of many of these accessions have been routinely cryopreserved at the USDA-ARS National Center for Genetic Resources Preservation (NCGRP) in Fort Collins, CO. In the standard procedure, dormant buds are sent to NCGRP in mid-winter. Scions are cut into 35 mm bud sections and desiccated at -5 degrees Celsius to a moisture content of 25 to 30% (fresh weight basis). Desiccated single-bud sections are sealed into polyolefin tubes, slow cooled at -1 degrees Celsius per hour to -30 degrees Celsius, held at -30 degrees Celsius for 24 hours, and then placed into the vapor phase of liquid nitrogen (LNV) for long term storage. For viability testing, one tube containing 10 dormant buds is rehydrated at 2 degrees Celsius in moist, sterile peat moss and then grafted onto rootstocks. In the 1990s, it was standard to process 60 dormant buds per accession and to use 12 of those buds to assess viability during the same season. This left a maximum of 48 buds in LNV per accession. In this analysis, successfully cryopreserved accessions were defined as those that have 40% viability and 19 or more predicted viable buds remaining in LNV. Of the 2302 accessions currently cryopreserved at NCGRP, 2023 accessions meet these requirements. An additional 31 accessions have at least 19 predicted viable buds in LNV, but have lower than 40% viability. Criteria were established to prioritize the 568 apple accessions that are either inadequately backed up at NCGRP or have not yet been processed. These criteria include the likelihood of success in cryopreserving the Malus taxon, the vulnerability of the field trees, the number of viable buds currently stored in LNV, and previous failures in response to the standard procedure.