Submitted to: Acta Horticulturae
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/15/2006
Publication Date: 5/15/2008
Citation: Reed, B.M., Hummer, K.E., Chang, Y., Gupta, S. 2008. MEDIUM AND LONG-TERM STORAGE OF RUBUS GERMPLASM. Acta Horticulturae. 777:91-98. Interpretive Summary: The United States Department of Agriculture, Agricultural Research Service National Clonal Germplasm Repository at Corvallis, Oregon, preserves genetic resources for Rubus.More than 1500 blackberry and raspberry cultivars and species are held in the collections of the USDA-ARS National Clonal Germplasm Repository at Corvallis. The main collections are potted plants in screenhouses with tissue cultures as a secondary backup and cryopreservation (storage in liquid nitrogen) as the long-term storage option. The tissue culture collection includes about 200 accessions. In vitro cold storage of these accessions is at refrigerator temperatures with 12 h of low light. Storage facilities for tissue culture collections vary, however 45° F storage in the dark or with a low light appears to be acceptable for most raspberry and blackberry types if they are evaluated on a regular basis and moved to room temperature when they decline in health. Cold sensitive and tropical genotypes which typically survive only a short time in cold storage can be stored at room temperature on a special medium. The shoot tips of cold-acclimated cultivars and species of Rubus (blackberry and raspberry) can be successfully stored in liquid nitrogen. Cold acclimation (CA) treatment improved the recovery of shoot tips cryopreserved by the slow freezing method. Regrowth was greatly improved by increasing the length of CA before freezing. Shoot growth was also increased by modifying the shoot recovery medium. A protocol for cryopreservation of Rubus germplasm should include a CA period of 6-10 weeks and recovery on a modified medium.
Technical Abstract: The United States Department of Agriculture, Agricultural Research Service, National Clonal Germplasm Repository at Corvallis, Oregon, preserves genetic resources for Rubus. The in vitro collection includes about 200 accessions. In vitro cold storage of these accessions is at 4°C with 12 h of low light. Storage facilities for germplasm collections vary however one week of cold acclimation followed by 4° C storage in the dark or with a photoperiod is acceptable for most Rubus germplasm when quarterly evaluation inventories are used to determine timing of repropagation. A reduced-nitrogen medium extends room temperature storage to nine months and is a useful alternative for cold sensitive and tropical genotypes which typically only survive for a short time in cold storage. Meristems of 34 cold-acclimated genotypes of Rubus (blackberry and raspberry) were successfully cryopreserved by slow cooling through optimization of cryoprotectants, cooling rates and cold acclimation. Alternating low temperatures as a cold acclimation (CA) treatment improved recovery of shoot tips cryopreserved by slow freezing. The length of the CA required varied from 1 to 10 weeks and was genotype dependent. Cryopreserved Rubus shoot tips produced shoots directly from either apical meristems or axillary buds but not from callus. Shooting increased and callus formation decreased when IBA was eliminated from the recovery medium. Shoot tips of 25 genotypes in 9 Rubus species were successfully cryopreserved using encapsulation-dehydration with recovery of 60-100%. Four genotypes of 3 species were tested using PVS2 vitrification with 71% average regrowth. A protocol for cryopreservation of Rubus germplasm should include a CA period of 2-10 weeks and recovery on auxin-free medium. These studies confirm that all three cryopreservation protocols may be used for cryopreservation of a wide range of Rubus genetic resources.