Welcome to the Clonally Maintained Plant Germplasm Cryopreservation Program

Plants that do not produce seeds, or if grown from seeds would not result in the same appearance and characteristics as the original plant, are propagated vegetatively or clonally. Examples of plant tissues that can produce a whole plant include shoots, root or stem fragments, dormant buds, or somatic embryos. Plants resulting from these plant parts are called clones because they will have the same qualities as the donor plant. For this reason these plant tissues can also be used in the cryopreservation of clonally propagated accessions.

Our program preserves genetic resources provided by the crop-specific active field sites of the National Plant Germplasm System (NPGS) and selected Plant Variety Protection (PVP) voucher samples. Currently, the majority of cryopreservation techniques for clonally maintained germplasm use tissue culture.

However, the PAGRPRU also preserves plant material as dormant winter buds. The choice of tissue being cryopreserved depends on availability of reliable cryopreservation protocols. In close collaboration with the NPGS curators, the group carries out applied research that improves and/or develops cryopreservation techniques that promote efficient long-term germplasm storage.

Some of our current research projects focus on:

• Establishing optimal harvest time for almond (Prunus dulcis), apricot (P. armeniaca) and blueberry (Vaccinium hybr.) dormant winter buds used for cryopreservation.

The ability of buds to survive low temperatures (-158 to -196°C) during storage depends on several factors; one of the factors is the sugar concentration at the time of cryoprocessing. The sugar concentration in dormant buds  changes as the tree physiological stages change.

Analyzing the sugar concentration over a growing season and correlating it with post cryopreservation survival will help to determine the optimal harvest time for the bud long-term storage in liquid nitrogen.

• Developing procedures for long-term storage of cacao (Theobroma cacao) genetic resources.

Cacao genetic resources are difficult to cryopreserve. Seeds of cacao are considered as recalcitrant in storage; cacao cultivars or selections are preserved vegetatively.

Our project studies the suitability of different plant tissues for storage in liquid nitrogen, pre-treatment procedures and testing techniques for viability after cryopreservation to determine the most suitable method for long-term storage of cacao vegetatively maintained germplasm.

• Improvement of cryopreservation techniques for pineapple (Ananas spp.) cultivars, selections and breeding lines.
  
  After cryopreservation viability of different pineapple genotypes varies. This project evaluates the fitness of available cryopreservation techniques for long-term storage and tests different pretreatments to improve survival of meristematic shoots in liquid nitrogen.