Ironing Out Storage Kinks for Hops
January 17, 2008
To help breeders improve hops for
brewing and other U.S. industries, the Agricultural Research Service (ARS) National Clonal Germplasm Repository
maintains a diverse hop collection at Corvallis, Ore. There, scientists and
curators maintain germplasmgenetic material such as plants, shoot tips
and seedsfrom more than 150 hop varieties collected from over 24
countries, from the Yugoslavian Ahil to the Czech Zlatan.
They cultivate about 250 accessions as potted plants and preserve 57
accessions as tissue cultures. Thirty accessions are also
cryopreservedstored frozen in liquid nitrogen for extended
Center for Genetic Resources Preservation in Fort Collins, Colo. The tissue
cultures can be stored at about 39 degrees Fahrenheit for two years or longer.
Reed and NCGR colleagues investigated how 12 hops genotypes responded to
the iron formulation used in the culture medium during storage. Their
observations have led to improved storage techniques.
Just as an adult recovering from surgery and a teenager preparing for a
marathon will have different dietary needs, the nutrient requirements of plants
vary according to their developmental stage and storage environment.
Identifying the precise requirements is essential to successful germplasm
In the past, NCGR scientists noticed that hop cultures stored on a standard
medium containing a moderate level of iron sometimes emerged iron-deficient
when grown out later. They learned that adding sequestrene iron to the growth
medium enabled most cultured plants to grow better.
But Reed and her colleagues also observed something paradoxical about the
iron-rich media. Although most hops cultivars grew better in an iron-rich
culture, the scientists found that they stored better in an environment with
The researchers have since modified their storage procedure accordingly,
reducing the iron content of the plants' media about a month before storage.
This reduces iron deficiency without compromising the accessions storage
more about this research in the January 2008 issue of Agricultural
ARS is the U.S. Department of
Agriculture's chief in-house scientific research agency.