CPC Best Plant Conservation Practices

to Support Species Survival in the Wild

Key Messages about Splitting Samples for Safety Duplication Storage and Testing
  • The old adage “Don’t put all your eggs in one basket” applies to seed banking. Divide each accession and store each half at a different safe seed banking facility.
  • Create curation packages to place inside storage packages. Seeds in curation packages can be used for testing initial and long-term viability. Seeds in storage packages are intended to be stored long-term.
  • Understand the rules of your storage facility and storage agreement.
  • Make a collection that is as large as is feasible to account for testing needs and future conservation actions.
  • For small seed collections, it may be necessary to grow plants and collect next generation seeds for testing and storing.

CPC seed collections are valuable for the conservation of rare plants. CPC recommends dividing collections to ensure that the representative samples of seeds will be safely duplicated to mitigate for loss caused by natural or human-caused catastrophes. Divisions into curation packages enable us to protect the long-term storage packages while we gain information about seed characters, their cultivation, and storage capacity.

Determine storage facilities.

  • For each accession, determine the primary and backup facilities for long-term storage. The backup facility should be geographically separate, politically stable, and relatively safe from natural catastrophe with the same or better conditions as those of the primary seed bank.

Plan for safety duplication agreements.

  • Any safety duplication arrangement requires a clearly signed, legal agreement between the depositor and backup institution.
  • The agreement should clearly detail the responsibilities of the parties and terms and conditions under which the material is maintained.
  • The primary site long-term storage institution may be a CPC institution and the backup institution can be the National Laboratory for Genetic Resources Preservation (NLGRP) in Fort Collins, Colorado.
  • CPC has a Material Transfer Research Agreement (MTRA) with NLGRP available to all participating institutions. The MTRA covers CPC Participating Institution seed accessions transferred to and stored for research purposes at NLGRP. Through the CPC Resources section of this site, CPC members of Participating Institutions have access to an accession submission online form that facilitates data transfer to NLGRP under this agreement. Each Participating Institution may also develop a separate black-box storage agreement with NLGRP.

Remember to allocate seeds for testing and curation

  • A portion of each accession will be used to gather information about percent germination, propagation, and longevity in storage.
  • This is one of the reasons for making a collection that is as large as is feasible (ideally 3000 seeds).


Germination Testing

Cheryl Birker, Rancho Santa Ana Botanic Garden The California Seed Bank at Rancho Santa Ana Botanic Garden has a germination testing program to monitor the... Read More

For collections with fewer than 100 seeds, there are special considerations.

  • Recognize that a small collection will require more work to have the best conservation value. Attrition or mortality of a portion of any seed collection should be expected after seeds are stored, germinated, or grown in a greenhouse (Guerrant and Fiedler 2004, Guerrant et al. 2004). Starting a conservation collection with as many seeds as is feasible helps ensure that adequate genetic diversity remains for conservation actions.
  • Use the seeds for propagation trials and seed bulking. Collect and store the first generation offspring (F1 generation). Note that this will require meticulous conservation horticultural care and require high maintenance. At your institution, assess your ability to maintain meticulous labels and records of maternal lines. Engage another CPC Participating Institution or partner willing to house and manage a nursery collection if necessary. See CPC Best Practice Section “Curating Small Samples: Increasing the Number of Seeds for Storage and Restoration.” FAQ: If I have maternal  line seed lots with fewer than 50 seeds, should I divide these low-producing lines?
  • Schedule additional seed collections from the wild population to increase the total number of seeds that can be used for storage and testing.
  • Consider collecting tissue for tissue culture. Engage a partner with expertise in tissue culture if necessary

For collections with greater than 100 seeds, divide the sample.

  • Divide to accommodate long-term storage, testing, and sample maintenance.
  • Divide each maternal line into packages for storage and curation: (1) primary institution long-term storage, (2) backup institution long-term storage, (3) curation package for primary institution, and (4) curation package for backup institution (Figure 1.4).
  • For long-term storage, place approximately 40% of the seeds of each maternal line into a package for primary and backup institution (see steps 1 and 2 in maternal lines of an accession. Each envelope should be marked clearly and neatly on the lower portion of the envelope with the accession number and maternal line number (for example, 2018-0075, #32).
  • Curation packages of cleaned seeds containing approximately 10% of total accession are needed for primary and backup institutions (see steps 3 and 4 in Figure 1.4). The seeds from maternal lines should be bulked in the curation package for NLGRP with even representation across total maternal lines collected. The primary institution may use the curation package to test germination of the accession and develop propagation protocols. Some tests may best be done with maternal lines bulked, but if using the seeds for reintroductions, keep maternal lines separated (see CPC Best Practice Chapter “Genetic Guidelines for Acquiring, Maintaining, and Using a Conservation Collection”). The backup institution may use the curation package to gather information about seed characteristics and longevity in storage. Clearly mark the curation package “Curation” and place inside the large storage package (see steps 3 and 4 in Figure 1.4). Curation packages can be easily removed from the main storage package, thus avoiding the problem of exposing the entire collection of stored seeds to changing temperatures.
  • If a single maternal line has less than 20 seeds, but the whole sample has at least 300 seeds, don’t divide the single maternal line. Rather, delegate it to one of the long-term storage groups. It is possible to use only fecund maternal lines with abundant seeds for trials to learn how to propagate the species.
    • If there is a particular interest in evaluating differences across maternal lines, then curation packages would need to be separated by maternal line. Prior arrangements would need to be made with the backup institution to test by maternal line and would require a research proposal and funding support.

Figure 1.4 –Steps for splitting accessions. Steps for splitting accessions by maternal line for duplicate storage and testing.

Send seeds and relevant accession data to the backup institution.

  • Information should be safely duplicated in a database at the backup institution.
  • Tracking the destination of maternal lines can be done by accessioning each maternal line or by notation in the comments fields of database.
  • For the rarest species, it is advisable to track maternal lines separately in the accession, seed germination, and propagation databases.

International Standards

Reference for CPC Guidelines
FAO Genebank Standards for Plant Genetic Diversity (FAO 2014)
Standards for Safety Duplication
4.9.1 A safety duplicate sample for every original accession should be stored in a geographically distant area, under the same or better conditions than those in the original genebank.
4.9.2 Each safety duplicate sample should be accompanied by relevant associated information
MSB Partnership Collections (Millennium Seed Bank Partnership 2015)
Storage and duplicaton
3.5 Collections are duplicated at –20°C ± 3 °C and 15% eRH ± 3% at a second, geographically-separate, facility or reason for non-duplication recorded (reasons include: low seed number, accession being regenerated and/or on priority list for recollection).

Food and Agriculture Organization of the United Nations (FAO). 2014. Genebank standards for plant genetic resources for food and agriculture. Rome, Italy. http://www.fao.org/3/a-i3704e.pdf.

Guerrant, E. O., Jr., and P. L. Fiedler. 2004. Accounting for sample decline during ex situ storage and reintroduction. Pages 365–385 in E. O. Guerrant, Jr., K. Havens, and M. Maunder, editors. Ex situ plant conservation: supporting species survival in the wild. Island Press, Washington, DC.

Guerrant, E. O., Jr., K. Havens, and M. Maunder, editors. 2004. Ex situ plant conservation: supporting species survival in the wild. Island Press, Washington, DC.

Millennium Seed Bank Partnership (MSB). 2015. Seed conservation standards for “MSB Partnership Collections.” Royal Botanic Gardens, Kew, UK.

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