Sudden Death Syndrome Spreads in Midwest
Sudden death syndrome (SDS) is slowly spreading its way through the
upper Midwest. The soybean disease has caused significant losses in
several Midwestern states for more than 20 years. However, it was only
first discovered in southeastern Minnesota in 2002. At the end of the
2007 growing season, SDS had been confirmed in 21 Minnesota counties.
Dean Malvick, plant pathologist at the University of Minnesota, is tracking
the movement of SDS across Minnesota. SDS has the potential to be a
big production threat across the southern half of the state. When conditions
are right, it’s a definite risk. In 2007, Minnesota experienced
a hot and dry growing season. But in a normal growing year, SDS would
be a threat. In 2006, the southern half of Minnesota had abundant rainfall
that created high occurrences of SDS in some fields.
Sudden death syndrome tends to develop where adequate to excess rainfall
has occurred. The disease typically develops in patches, often one to
two acres in size. It frequently is found in fields with moderate to
high populations of soybean cyst nematode. It is caused by a soil-borne
fungal pathogen that infects the roots and lower stem. Yield losses
from SDS can exceed 60 percent in heavily infected areas.
There are many aspects to the checkoff-funded research conducted on
SDS. Most research is focused on the discovery of cultivars with improved
resistance to the pathogen. University researchers are screening public
and private soybean lines in greenhouse and field trials. Those with
improved resistance to SDS are incorporated into soybean breeding programs
across the United States.
Notable achievements:
As a result of checkoff-funded research, an early-maturity germplasm
line with improved SDS resistance will be released this month.
One hundred and eighty-seven soybean lines ranging from maturity group
I to IV were tested in 16 field environments.
The researchers made significant progress in better understanding the
epidemiology of the pathogen that causes SDS. They discovered that under
high inoculums pressure the disease progress was more significant on
leaves than roots. They also concluded that a threshold around 60 percent
root rot was necessary before a decrease in root biomass was observed.
