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United States Department of Agriculture

Agricultural Research Service

Apple Collection
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Apple DiversityPreservation of genetic diversity is the driving factor behind why germplasm repositories exist. The Malus collection is maintained on a 50-acre farm located one mile north of Geneva. Typically, two trees are maintained for each accession. Some accessions are also stored as cryogenically preserved buds. Over time, more and more of the Malus collection will be stored in this manner, in addition to it being preserved as orchard-grown plants.

"The Big Apple Family":  This mp3 file (24 MB) contains an interview with Phillip Forsline by Jean Feraca of Radio Without Borders (, a live global cultural affairs call-in program at Wisconsin Public Radio. Phil was interviewed for nearly an hour about his work to increase the diversity of apple germplasm in the USDA National Plant Germplasm Collection through his apple collections made to Central Asia, China, Russia and Turkey from 1993-1999 with international teams of scientists. He discussed why these collections are important and what is being done by the Plant Genetic Resources Unit in characterizing that apple germplasm here on site and with multiple collaborators world-wide.  He also answered questions about apple germplasm from individuals that called in during the program.

Bud Storage Process for Malus
Apple bud cutting
Bud segments being weighed
Drying buds in lab freezer

1. Single bud section 35 mm long with healthy bud being cut from dormant well acclimated scion.

2. 10 bud segments being weighed prior to desiccation and samples placed on wire drying rack.
3. Buds dried at -40°C in lab freezer modified with controller and heat tape.
Buds dried to 30%
aluminum cryo boxes
Boxes of buds frozen to -30C
4. Buds dried to 30% moisture and sealed in heat shrinkable tubes with birch plugs in both ends.
5. Multiple tubes each containing 12 bud segments placed in aluminum cryo boxes.
6. Boxes with buds frozen to -30°C in programmable freezer.
Boxes transferred to LN storage
330 Boxes can be stored in each tank
7. Boxes transferred to LN storage tank and held at almost -170 °C.
8. 330 boxes can be stored in each LN storage tank.

Bud Recovery Process for Malus
Chip bud cut from section
Thin chip bud for optimum recovery
1. Rehydration is accomplished using moist peat moss.
2. Chip bud cut from 35 mm bud section.
3. Thin chip bud for optimum recovery.
2 Chip buds are grafted to rootstock
Bud tying
Top of rootstock is cut after grafting
4. Two chip buds are then grafted to a seedling rootstock.
5. Careful bud tying.
6. Top of rootstock is cut 17 days after chip grafting buds.
Bud emergence and growth
Recovery tests in Greenhouse
7. Bud emergence and growth.
8. Recovery tests in progress in one of the PGRU greenhouses.

Bud Cutter Invention


This old axiom certainly holds true for the PGRU's Cryo Technician, Todd Holleran. As noted in the cryo bud storage page it is necessary to cut dormant scion of apple into 35 mm lengths with a single bud centered in each section. As the photo from the bud storage page shows, in the past it has been necessary to individually measure and cut each bud section to length. This old process required visual accuracy in measuring each section, and two separate cuts. Todd designed the device shown here to increase the accuracy of his work as well as his productivity. He also liked the added benefits of eliminating hand cramps from making so many cuts, as well as the increase in time for other projects.

Construction of this device was fairly simple. As can be seen, it is simply two pair of Felco® pruning sheers separated by a wooden spacer. The device is attached to a wooden base to provide stability. Two QuickGrip® clamps are used to hold the cutters, frame and spacer together. A small block of wood is duct taped to the two free handles of the pruners to deliver simultaneous cutting of the scion. Simple, easy to build, inexpensive and yet very functional.

In 1998, Todd's invention went international with the visit of Dr. John Warner of the Canadian Clonal Genebank of Harrow, Ontario. Dr. Warner was visiting the site to learn more about the cryogenic storage and recovery process of Malus budwood. During Dr. Warner's visit he took note of the device, and commented on its functionality and ease of use. Wanting to build a replica upon his return to Canada, we had these photos taken for future construction reference. The National Plant Germplasm System has been housing the Canadian Malus clonal germplasm collection in cyrogenic storage during the move of the entire collection from its old home in Trenton, Ontario to its new permanent location in Harrow, Ontario. Dr. Warner noted that he wished they had this device available when they needed to prepare their collection for storage.

Last Modified: 9/13/2013