Illinois College of ACES
Developing red leaf blotch resistant soybeans through research in
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[November 06, 2019]
The United States
is the world’s leading producer of soybean and the second-leading
exporter. Nearly 90% of oilseed production in the U.S. comes from
soybean. A biological threat to soybean crops in America could
affect the global economy, and the result could be devastating to
the American soybean farmer, according to researchers in the USAID
Soybean Innovation Laboratory (SIL), housed in the College of
Agricultural, Consumer and Environmental Sciences at the University
The Federal Select Agent Program (FSAP) was established to
regulate the possession, use, and transfer of select biological
agents and toxins that could potentially pose a severe threat to
public, animal, or plant health following the anthrax attacks
that occurred in 2001. Bioterrorism is typically associated with
toxins such as ricin or diseases such as smallpox or the bubonic
plague. However, bioterrorism can also take the form of plant
pathogens such as bacteria and fungi.
There are 67 select agents and toxins on FSAP’s list that are
considered to have the potential to pose a severe threat, and
seven of these are categorized as USDA Plant Protection and
Quarantine (PPQ). This means that if any of these seven select
agents or toxins were exposed in the U.S., they could pose a
severe threat to American plant health.
Number 61 on the Select Agent and Toxin list under the PPQ
category is the fungus Coniothyrium glycines, the cause of a
soybean disease referred to as red leaf blotch (RLB). The
disease is native to Africa and currently affects soybean in
central and southern Africa. Sub-Saharan African countries have
reported soybean production losses of up to 70% due to RLB. The
first cases of RLB were reported in Ethiopia in 1957; yet, very
little is known about the fungus today. The U.S. and Brazil now
recognize RLB as a major potential threat to soybean production,
but research on how to combat the fungus is limited.
“Just like disease-causing pathogens of humans, there are
disease-causing pathogens of soybean. One of these diseases is
red leaf blotch, which occurs in Africa. The disease is
important because it reduces soybean yields where it is endemic
to some locations in Africa,” says Glen Hartman, a crop
scientist in the College of ACES at U of I.
Hartman serves as plant pathologist for USDA Agricultural
Research Service (ARS) and collaborates with SIL on researching
RLB. He says that finding resistance in other exotic lines could
provide soybean breeders with germplasm to develop resistant
cultivars. However, there has been little progress made on
discovering sources of resistance to the fungus that causes RLB.
“Our research through SIL focuses on developing disease
management techniques to control red leaf blotch that would be
useful to African soybean producers, as well as U.S. soybean
producers,” Hartman says.
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Hartman received funding from USDA-ARS to evaluate
soybean genotypes for resistance to RLB. However, because C.
glycines is on the Select Agents and Toxins list, it is nearly
impossible to conduct research on the disease in the U.S. SIL
manages 72 field sites across 14 countries in West, East and
Southern Africa through the Pan-African Soybean Variety Trial (PAT)
program, many of which have reported cases of RLB.
Post-doctoral fellow and SIL research partner Harun Murithi, who
collaborated with Hartman to develop SIL’s Field Guide to African
Soybean Diseases and Pests, will be conducting on-site research at
SIL’s PAT sites in Ethiopia, Malawi, Tanzania, Rwanda, Uganda, and
Zambia. Hartman and Murithi will evaluate the severity of RLB at
several of these sites.
Hartman explains that seeds of the best genotypes will be retested
at the Foreign Disease-Weed Science Research Unit (FDWSRU) at Fort
Detrick, Maryland. Once the analyses confirm resistance, results
will be disseminated through SIL’s global network of soybean
breeders. Breeders in the U.S., as well as Africa, can then use
these sources of resistance to make crosses and develop soybean
populations with resistance to RLB.
“While red leaf blotch has not yet been reported outside of Africa,
the potential threat exists, making it critically important to
prepare for the possibility that American soybean crops could be
exposed to the fungus that causes RLB, whether intentionally or
unintentionally,” Hartman concludes. “Developing soybean lines with
resistance to RLB will not only lead to improved soybean production
across sub-Saharan Africa, but will also prevent potentially
disastrous effects on the U.S. soybean crop.”
[Source: Glen Hartman
Writer: Amy Karagiannakis]