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United States Department of Agriculture

Agricultural Research Service

Title: Plant Diseases Impact USDA Clonal Vaccinium Genebank

Authors
item Postman, Joseph
item Oliphant, James
item Hummer, Kim

Submitted to: Acta Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 13, 2007
Publication Date: March 1, 2009
Citation: Postman, J.D., Oliphant, J.M., Hummer, K.E. 2009. Plant Diseases Impact USDA Clonal Vaccinium Genebank. Acta Horticulturae. 810:319-324.

Interpretive Summary: The USDA Agricultural Research Service maintains a collection of Vaccinium species from around the world at the National Clonal Germplasm Repository, a genebank in Corvallis, Oregon. This collection includes more than 600 blueberry, lingonberry and cranberry varieties. The primary collection was previously maintained as a field planting, but because of the presence of two plant diseases spreading in western Oregon, the Vaccinium collection is now grown as potted plants in a screenhouse. Migration to a screenhouse necessitated development of a management strategy that maintains the plants in a vigorous condition to provide high quality cuttings for propagation. Trials were conducted to select a potting medium with good fertility that does contain bark like most nursery potting soils. The potted blueberry plants should be able to grow for 8-10 years in the same soil, but media containing bark do not last that long. A blend of volcanic pumice (50%), peat moss (40%), and mineral loam (10%) was selected. A 3-5 cm deep pumice top-dress (collar) is added to the surface of each pot to create a sterile, dry, inorganic surface that prevents weed, moss and fungus gnat growth. This top-dress combined with a stable, bark-free medium creates a growing system that greatly reduces water use, nutrient leaching, salt build-up, and moisture stress. Woody Vaccinium clones are hard pruned in late winter to remove all flower buds and six to eight upright shoots are selected and allowed to grow. These shoots provide cuttings that are distributed by the genebank for research or propagation.

Technical Abstract: The USDA Agricultural Research Service maintains a diverse collection of Vaccinium genotypes at the National Clonal Germplasm Repository, a temperate fruit and nut genebank in Corvallis, Oregon. Vaccinium species are hosts for two emerging diseases in the U.S. Pacific Northwest that impact the collection management. One is the fungus Phytophthora ramorum and the other is blueberry shock ilarvirus. Phytophthora ramorum is a devastating pathogen of certain oak species and can also cause a foliar blight in some Vaccinium species. Vaccinium germplasm must be inspected and certified free of this pathogen to protect the U.S. nursery industry. The pollen borne blueberry shock virus has made it necessary to move the primary Vaccinium clonal collection from a field planting to a potted screenhouse collection. More than 600 clonal accessions are maintained as potted plants in greenhouses or screenhouses, protected from pollinators and other virus vectors. These clonal accessions represent more than 60 unique Vaccinium taxa from around the world and include 167 cranberry, 45 lingonberry, 14 lowbush blueberry and 158 highbush or rabbiteye blueberry genotypes. Migration to a screenhouse necessitated development of a management strategy that maintains the collection in a vigorous condition to provide high quality vegetative growth suitable for propagation. Trials were conducted to select a medium with good fertility and porosity that would be stable for an expected 8-10 year lifespan of a potted blueberry plant. A blend of volcanic pumice (50%), un-milled, coarse, sphagnum peat moss (40%), and mineral loam (10%) was selected. A 3-5 cm deep pumice top-dress (collar) is added to the surface of each pot to create a sterile, dry, inorganic surface that prevents weed, moss and fungus gnat growth. This top-dress combined with a stable, bark-free potting medium creates a growing system that greatly reduces water use, nutrient leaching, salt build-up, and moisture stress. Woody Vaccinium clones are hard pruned in late winter to remove all flower buds and 6 – 8 upright shoots are selected and allowed to grow. These shoots provide cuttings that are distributed by the genebank for research or propagation.

Last Modified: 9/2/2014
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