Organic Farmer June 2019

Organic Carrot Breeding
Delivers Novel Varieties,
Cutting-edge Research for
Vegetable Production
By KIKI HUBBARD | Organic Seed Alliance
All photos courtesy of Organic Seed Alliance.
THE U.S. ORGANIC INDUSTRY
continues to grow, with sales of
organic food reaching $47.9 billion
in 2018 and the number of organic
farms estimated at over 14,200. Organic
carrots increasingly make up a larger
share of overall carrot production—14
percent of the estimated 100,000 acres
of carrots grown in the U.S. are certified
organic (compared to three percent of
total vegetables grown organically).
Growing carrots organically isn’t easy,
however, given the extensiveness of
major diseases and pests, and the cost
of managing weeds. More than 80
percent of U.S. carrot acreage is infested
with one or more of the most common
pests or diseases: root-knot nematodes,
Alternaria leaf blight, and other foliar
and storage diseases, such as cavity spot.
The future of organic carrots therefore
relies on the development of effective,
non-chemical methods for addressing
these challenges, including managing
weeds in this slow-to-establish crop.
Breeding a Key Factor
“Organic farming takes a whole-systems
approach to addressing plant nutrition
and challenging weeds, diseases, and
pests,” says Micaela Colley, program
director for Organic Seed Alliance. “In
important ways, organic growers rely
on the genetic characteristics of the
seed they plant even more than other
growers, since most pesticides and
fertilizers are not allowed under organic
regulations.”
“That’s where plant breeding comes in,”
Colley adds.
Seed provides growers the genetic tools
to confront day-to-day challenges in
the field, and breeding plants in the
environment of their intended use—in
this case, under organic conditions—
can yield many benefits. Enter the
Carrot Improvement for Organic
Agriculture (CIOA) project, a multiregional
plant breeding collaboration
between the United States Department
of Agriculture’s (USDA)/Agriculture
Research Service (ARS), University of
Wisconsin-Madison, Purdue University,
University of California-Riverside,
Organic Seed Alliance, and Washington
State University. It is the first publicly
funded organic carrot breeding project
in the U.S., and the USDA’s Organic
Research and Extension Initiative
(OREI) grant program recently awarded
the project a second round of fouryear
funding—and for good reason.
The project’s successes thus far are
noteworthy.
Dr. Philipp Simon is the coordinator of
CIOA and has been breeding carrots
for 40 years. He holds a joint position
with USDA ARS and the University
of Wisconsin-Madison’s Horticulture
Department. Simon has learned a lot
in the last decade about the needs
of organic carrot growers and how
CIOA can turn their production
challenges into breeding opportunities.
To that end, CIOA’s main goal is to
develop orange and novel colored
carrots with improved disease and
nematode resistance, improved weed
competitiveness, and better nutrition
and flavor. That’s quite the genetic
package, but progress toward releasing
new varieties has been efficient—and
relatively quick—thanks to the project’s
variety trial network that expands
across the U.S.
Variety Trials
In 2018, CIOA variety trial sites were
located in California, Hawaii, Indiana,
Maine, Washington, Wisconsin,
Vermont, and Virginia. Each site
tested a different mix of 34 promising
advanced breeding populations (these
are varieties that are nearly uniform
enough to release commercially).
Simon is especially excited to see more
evidence that the most important
traits are “fixed.” This means that from
general appearance to disease resistance
to flavor, CIOA partners are finding
that the varieties in development are
performing relatively similar across trial
locations.
“From a breeding standpoint, the
process of putting together the right
combination of traits and then having
them reliably expressed across regions is
so important,” Simon explains. “CIOA’s
extensive trialing network is providing
us more confidence that certain traits
will express in varying environments,
allowing us to accurately report just
how well the overall varieties perform
in different regions across the U.S.”
Simon says that two traits in particular
are worth noting: top size and
nematode resistance. Research shows
that carrots with bigger tops help
suppress weeds, a costly production
challenge for all carrot growers, not
just organic. CIOA breeders have had
success in incorporating this trait into
breeding lines to support better weed
competition.
CIOA is also having success in breeding
orange and novel colored carrots that
demonstrate resistance to the two major
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Organic Farmer June/July 2019