National Laboratory for Genetic Resources Preservation Clonal Plant Program

Clonally propagated plants are those that are not propagated by seeds because they don’t produce seeds or because a specific genetic combination must be maintained through asexual propagation methods such as grafting, cuttings, runners, etc. The USDA National Plant Germplasm System (NPGS) has more than 40,000 accessions that are clonally propagated and maintained as actively growing plants in the field, greenhouse, screenhouse, or in vitro. These include many most fruit and nut and some ornamental and vegetable crops. These clonally propagated collections are particularly vulnerable because they are exposed to biotic (pests and pathogens) and abiotic stresses (extreme heat, cold, drought, and/or weather events) that could threaten their survival. NLGRP uses cryopreservation methods to back-up NPGS clonal collections in liquid nitrogen conditions so that they are secured at a secondary site.

NLGRP cryopreserves clonally propagated collections primarily as dormant winter buds or as tiny shoot tips.

NLGRP research teams adapt or develop new methods for cryopreservation and then implement those methods to secure collections. In addition, NLGRP cryopreserves the voucher samples for the Potato Plant Variety Protection program and maintains them for 20 years until they are publicly released through the NPGS.

NLGRP has over 5000 clonally propagated accessions cryopreserved as dormant buds and shoot tips, including (but not limited to): 

Dormant buds: apple, sour cherry, plum, currant, butternut, willow etc.

Shoot tips: citrus, garlic, potato, raspberry, blackberry, strawberry, mint, grape, sweet potato, pineapple, hops, and many more.

In some cases, cryopreservation methods are not available or NLGRP does not have the capacity to secure collections as dormant buds or shoot tips in liquid nitrogen. To a limited extent, pollen cryopreservation has also been employed for crops including date palm, Prunus, walnut, pecan, hazelnut, and pistachio.

In addition to developing and implementing cryopreservation methods, NLGRP research teams use genotyping and genomics to understand collection diversity, fill gaps through plant explorations, perform basic research to understand cryoprotectant behavior, cryotherapy, and much more.