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Clean Plant


Adding New Cultivars to NCPN Berries Centers and Initial Testing


Clean plant centers may receive plant material from a variety of sources. New cultivars may be introduced from breeding programs or heritage cultivars may come from a repository. In addition, some centers may accept material from outside the U.S. under a Controlled Import Permit.

In any case, all submitted material is fully tested for targeted pathogens (viruses, phytoplasma etc.).

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Gel shows separation of marker dyes after electrophoresis; this is used to separate PCR products. Upper right, ELISA plate shows positive samples (yellow). Lower right, symptoms on indicator plant shows mottling of leaves; this was from a plant that tested negative in all laboratory assays at the time.

AddingNew Culitvars
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Plants infected with a targeted pathogen are held at elevated temperatures, generally 35 - 40 C, for up to six weeks prior to meristem excision. 

Potted plants in a heat chamber.

Meristems Dissected


The meristems are dissected and grown in tissue culture.

meristem dissection video 

(opens new window in you tube). 


A set of 24 plants regenerated from individual meristems about 3 weeks post transfer.

Strawberry plantlets approximately 3 to 5 months after meristem dissection.

Plantlets Retested

The plantlets are planted in a greenhouse and then retested.

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Plantlets Restested

Further testing includes bioassays (right), ELISA and PCR assays, and High Throughput Sequencing (HTS).

Grafted plants are held in humidity chamber for 10 days.

First generation blocks established


Once the plants are fully tested and found free of targeted pathogens, the resulting plants are designated as G1 (first generation) and grown in protected environments and designated as G1 blocks.

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Potted G1 blackberry plants in a screenhouse at North Carolina State University.

Targeted and Cryptic Viruses


NCPN targets only a defined list of viruses for a given crop, since there may be a larger number of viruses that are not currently of concern. The viruses not on the targeted list, known as cryptic viruses, may not cause any symptoms and/or there are no known ways to eliminate them from a cultivar.

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G1 blackberry tissue culture plants in gas permeable plastic bags held at 4C in Corvallis, Oregon. Picture is about one year after transfer; these plants can survive up to three years without any maintenance.

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