8th INTERNATIONAL WHEAT CONFERENCE

deoxyNIVALeNoL LeVeL IN WheAT gRAIN hIghLy ASSo-
CIATed WITh PeRCeNTAge of SCABBy gRAIN CAuSed By
fuSARIum gRAmINeARum
P. Horevaj, D. Moon, and E. A. Milus
Department of Plant Pathology, University of Arkansas, Fayetteville, AR, USA 72701
E-mail Address of presenting author: gmilus@uark.edu
Head blight of wheat in North America is caused primarily by Fusarium graminearum,
but other Fusarium spp. can be important in other regions. Although head blight can
cause significant yield losses, mycotoxins such as deoxynivalenol (DON) and nivalenol
that are associated with affected grain are the greatest concern because of their negative
impacts on the health of humans and animals consuming the grain. Growing cultivars
with resistance to head blight is believed to be essential for managing the disease and
achieving low levels of associated mycotoxins in grain. Resistance to mycotoxin accumulation
has been hypothesized as one of the five types of head blight resistance. Relative
to the understanding of resistance to initial infection (type I) and spread within a spike
(type II), little is known about resistance to mycotoxin accumulation. The objectives of
this research were to develop an efficient method for selecting lines with low levels of mycotoxin
accumulation in grain and to determine if resistance to mycotoxin accumulation
is a separate, independent resistance component or simply a pleiotropic effect of other
resistance mechanisms.
A susceptible cultivar (Coker 9835) and 15 winter wheat lines with diverse sources of head
blight resistance were evaluated in three misted nurseries inoculated with maize kernels
infested with F. graminearum. Head blight severity at soft dough stage and percentage of
scabby kernels and DON level in grain after harvest were recorded. Correlation analyses
were performed to determine the relationships of head blight severity and percentage of
scabby grain with the DON level in grain. Preliminary analyses indicated that data for the
susceptible check had a disproportionate influence on the magnitude of the correlation coefficients
(i.e. correlation coefficients were close to 1), so data for the susceptible check were
deleted from the analyses to obtain more realistic correlation coefficients. DON levels in
grain were positively correlated with head blight severity at soft dough stage (r = 0.74 to
0.83) and with percentage of scabby grain (r = 0.89 to 0.95). Compared to DON levels for
the susceptible check, DON levels for resistant lines were reduced by 55 to 88%.
Twenty of the most commonly grown soft red winter wheat cultivars in Arkansas in 2008
and 2009 and lines from the 2008 and 2009 Southern Uniform Winter Wheat Scab Nurseries
were evaluated in the field in 2008 and 2009 as described above. For the Arkansas
cultivars, DON level in grain was positively correlated with percentage of scabby grain (r
= 0.71 and 0.79 in 2008 and 2009, respectively). For lines in the Southern Uniform Winter
Wheat Scab Nurseries, DON level in grain was positively correlated with percentage of
scabby grain (r = 0.70 and 0.85 in 2008 and 2009, respectively).
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