NorValley, Snowden, Dakota Pearl, NorDonna, NorChip, and Dark Red Norland
are a few notable graduates that have passed through the worksite's
doors en route to commercial success.
Besides helping with evaluations, Suttle conducts potato postharvest
physiology studies with ARS chemist Edward Lulai to decipher the biochemical
mechanisms that regulate sprouting and wound healing in stored tubers.
"Our research objective is to identify key physiological processes
that can be manipulated to improve postharvest storage," Suttle
Along with rot diseases and physiological disorders, such as tuber
shrinkage and sugar-end defect, wounds and sprouting cost the U.S. potato
industry and consumers more than $300 million annually in postharvest
losses. Such problems can claim between 5 and 40 percent of a stored
"Unlike grains such as corn that are stored dry, potatoes are
stored in a fully hydrated and highly perishable form," Suttle
explains. "Plus, the potatoes are stored uncleaned and at temperatures
favorable to attack by disease organisms."
Storage managers can manipulate the warehouse environment to promote
wound healing, but there isn't a product available for treating the
tubers directly, notes Suttle, who cites a lack of earlier, in-depth
research on the topic.
One possible lead may come from recent discoveries at Lulai's lab.
He demonstrated that natural waxes in a tuber's skincalled phenolic
and aliphatic polymersare needed to form a chemical barrier around
wound sites. This shield seals water in but keeps disease organisms
"Once you know what you're looking for," says Suttle of tuber
physiology, "you can genetically select for it or design specific,
environmentally benign compounds to manipulate key biochemical processes."
The Fargo researchers also apply that mindset to controlling sprouting,
which is undesirable in stored potatoes because it results in the loss
of both nutritional and processing qualities and favors disease development.
A chemical known as CIPC (isopropyl-N-[3-chlorophenyl]-carbamate) is
widely used to control sprouting. About half the nation's roughly $2.5
billion crop is treated with the chemical to extend storage time and
improve marketability. Despite such widespread use, CIPC faces ever-tighter
In seeking more benign alternatives, the Fargo lab has devised a novel
tissue culture technique for identifying dormancy-controlling hormones
and determining their interactions that ultimately lead to sprout growth.
Thus far, three key hormones have been identified in these studies:
abscisic acid and ethylene, which usher in dormancy; and cytokinins,
which stop it so sprouting can begin.
In the lab, the technique involves snipping a leaf from a very young
potato plant and placing it in an agar growth medium. Chemicals that
either inhibit or stimulate synthesis of hormones are added to reveal
their effects on tuber dormancy. Suttle says compounds that increase
abscisic acid or ethylene levels lengthen dormancy, while chemicals
that block abscisic acid and ethylene synthesisor stimulate cytokinin
"With the tissue culture system, you can manipulate the chemical
and physiological environment as the potato plantlet or tuber grows,
right from the start, and see how that affects tuber dormancy,"
Suttle explains. "It's an experimental system that opens avenues
you just can't follow with field studies."
In other work, Suttle says, "We're pushing hard to develop our
program in the postharvest maintenance of value-added traits, such as
vitamins, nutraceuticals, and proteins, or medically important materials
such as antibodies. Postharvest storage deterioration affects all aspects
of potato composition, including these traits."By Jan
Suszkiw, Agricultural Research Service Information Staff.
This research is part of Quality and Utilization of Agricultural
Products, an ARS National Program (#306) described on the World Wide
Web at www.nps.ars.usda.gov.
Martin T. Glynn
is at the USDA-ARS Potato
Research Worksite, 311 5th Ave. NE, East Grand Forks, MN 56721;
phone (218) 773-2473, fax (701) 795-8348.
Edward C. Lulai and Jeffrey
C. Suttle are in the USDA-ARS Sugarbeet
and Potato Research Unit, P.O. Box 5677, 1307 18th Street N., Fargo,
ND 58105-5677; phone (701) 239-1257, fax (701) 239-1349.
"Spud Hub" Tests Potatoes' Fitness for Market"
was published in the July
2003 issue of Agricultural Research magazine.