Building a Better Blueberry
Geneticist Lisa Rowland
(front) and horticulturist
Elizabeth Ogden collect
blueberry plant leaf tissue
for DNA analysis.
Scientists with ARS
have recently worked out a system to regenerate blueberry plants from
plant tissue taken from the commercially important cultivar, Bluecrop.
Regeneration is a delicate but necessary process used
to produce whole plants from cells that have been pegged as genetically
superior or have undergone genetic improvement. It is important to scientists
working to develop cultivars endowed with desirable genetic traits.
Though an efficient system for regenerating plants had
been devised for several other blueberry cultivars, it did not work
for Bluecrop until recently.
Bluecrop is known for its widespread acreage and its good
fruit yield nationwide. It is the most widely grown highbush blueberry
in the United States.
ARS Fruit Lab researchers
devised a method for
regenerating the Bluecrop
blueberry cultivar from
tissue culture. Here,
technician Stephanie Ray
(left) and plant physiologist
Freddi Hammerschlag examine
Bluecrop shoots growing on
| Among other projects, scientists
with ARS' Fruit Laboratory in Beltsville, Maryland, are using gene transfer
followed by the regeneration process to study blueberry genes believed
to be associated with cold tolerance. Plant physiologist Freddi A. Hammerschlag
heads the project. She and plant geneticist Lisa J. Rowland hope to improve
Bluecrop's already good cold tolerance.
The process starts by developing many Bluecrop shoots
with which to work. Tiny shoots, which are actively growing vegetative
buds, are put into large tissue culture dishes containing nutritive
ingredients. Inside, the shoots grow and propagate. Next, tiny sections
called explants are taken from shoots of the propagated test plants
and placed onto a regeneration medium. It was explants from these Bluecrop
shoots that ultimately proved to regenerate.
"We applied a two-step pretreatment to the tissue
before its transfer onto the medium. That was key to enabling regeneration,"
Now the team is building on that success.
Rowland has identified and isolated several genes from
other blueberry cultivars that are believed to be involved with cold
tolerance. Hammerschlag has developed a procedure to promote transfer
of one of the new genes into Bluecrop cells. She then takes cells that
receive the new gene and puts them onto a regeneration medium containing
various additives, such as nutrients and growth regulators.
The last step is regenerating new plants endowed with
the introduced gene. During this end stage, the regeneration medium
includes an ingredient that targets growth. "Only the cells containing
the new gene can develop, regenerate, and thrive," says Hammerschlag.
The final phase is to evaluate whether full-fledged plants grown from
the gene-enhanced cells perform better under colder-than-normal conditions.
Improving cold tolerance is a challenging science. For
example, the developers of the cultivar Arlen, named after retired USDA
blueberry geneticist Arlen Draper, hoped the plant would flourish in
New Jersey. But Arlen was not sufficiently winter hardy to grow in that
region, so it was released to growers farther south, in North Carolina.By
Rosalie Marion Bliss,
Agricultural Research Service Information Staff.
This research is part of Plant Biological and Molecular
Processes, an ARS National Program (#302) described on the World Wide
Web at http://www.nps.ars.usda.gov.
Freddi A. Hammerschlag and Lisa J. Rowland are with the USDA-ARS Fruit Laboratory, 10300 Baltimore Blvd., Bldg. 010A, Beltsville, MD 20705-2350; phone (301) 504-6647[Hammerschlag], (301) 504-6654 [Rowland], fax (301) 504-5062.
of a Media Darling
Blueberries are increasingly popular as more consumers reach for the
fruit that's high in antioxidants and long on taste. Antioxidants shield
cells from the plundering effects of free radicals. These rogue molecules
corrupt healthy cellsa process that ultimately underlies cellular
aging. With such high-stakes health benefits, it's no wonder blueberries
have become a media darling among the food press.
Blueberries are among the fruits and vegetables highest in antioxidant
capacity, according to tests developed by ARS, says Ronald L. Prior,
chemist with the Arkansas Children's Nutrition Center in Little Rock.
Preliminary research in rats shows blueberries may also improve cognitive
functiona term scientists use for mental capacities, such as memory
"Our research on aging shows that blueberry supplementation at
about 1 to 2 percent of the diet may reverse short-term memory loss
and improve motor skills," says James A. Joseph, physiologist at
the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts
University in Boston, Massachusetts.
Consumption has never been higher. More cultivated fresh blueberries
and more frozen wild ones were consumed or purchased through U.S. supermarkets
last year than ever before, according to industry experts. U.S. growers
produce about 350 million pounds of blueberries worth between $187 million
and $260 million annually.
Blueberry's powerful nutritional punch is likely due to the fact that
its antioxidants come in the form of both long-established vitamins
and newly defined phytochemicals. The berries are particularly
well endowed with a series of phytochemicals called anthocyaninsthe
source of their blue, purple, and red pigmentsand proanthocyanins.
Also, blueberry is one of the few fruits that contain so wide a spectrum
of anthocyanins, which fall within a phytochemical class called flavonoids.
Another class, carotenoids, makes carrots and pumpkins orange.
Naturally, the amount of nutrients in any crop may differ among varieties
or because of growing conditions, such as geographic location and soil
content. Still, while many fruits contain only about 3 to 6 individual
anthocyanins, various cultivated blueberries contain about 15 on the
low end, rising to about 25 in wild blueberries, says Prior.
In test tubes, these anthocyanins yield about 2 to 2.5 times the antioxidant power of vitamin C. The next step, now under way, is to assess the bioavailability of these antioxidant heavyweights. Bioavailability refers to how well the body digests, uses, and stores a given chemical. Stay tuned.By Rosalie Marion Bliss, ARS.
"Building a Better Blueberry" was published in the November 2002 issue of Agricultural Research magazine.