Title: Interactions of Genetic Traits, Agronomic Conditions, and Prior Insect Damage on Postharvest Insect
1Interactions of Genetic Traits, Agronomic
Conditions, and Prior Insect Damage on
Postharvest Insect Resistance in Montana Hard
Wheat Varieties Matthew J. Broughton and Florence
V. Dunkel, Department of Entomology, Montana
State University-Bozeman
Introduction Recent research in our laboratory, i
ndicates differences exist in postharvest storage
hardiness of popular varieties of Northern Great
Plains wheat Triticum aestivum L. These
significant differences can be exploited to
provide no cost, no thought protection from
insect damage during storage. For example, even
in low moisture harvest and storage conditions of
Montana (9-10 wheat moisture content), the most
destructive stored grain insect, the lesser grain
borer, Rhyzopertha dominica (F.) (Coleoptera
Bostrichidae), can thrive and severely damage the
endosperm of hard spring and winter wheat (Sinha
et al. 1988, Watts and Dunkel 2003). Past studies
have shown postharvest resistance differences
exist between varieties within class (Rao and
Wilson 1972, McGaughey et al 1990, Singh and
Singh 1995, Toews et al. 2000, Watts and Dunkel
2003). Protein analysis and hardness were not
factors contributing to relative hardiness of
wheat (Watts and Dunkel 2003). Seed chemicals can
confer resistance to stored wheat kernels (Yetter
et al. 1979). Yet, it is still unknown where
exactly these chemicals reside in the kernel and
which currently most popular Northern Great
Plains varieties have the best defenses against
postharvest attack.
Conclusions We have now learned that P. interpunc
tella, once thought to be not a major problem in
wheat because it only consumes the germ,
actually can damage more than germ in hard wheat
kernels and can make resistant wheat kernels
vulnerable to R. dominica when acting
collaboratively during storage. For R. dominica
we have found there is a pericarp / seedcoat
factor in popular hard red spring wheat varieties
slowing feeding damage. In Penawawa we found a
resistance factor in the endosperm. This may be
genetically conferred. We are currently
determining which properties of popular Northern
Great Plains wheat varieties afford protection
from both of these destructive insects. We,
therefore, accept the hypothesis that seed coat
factors confer resistance to R. dominica, but we
saw an agronomic practice (dryland vs. irrigated)
with Ernest that causes us to hesitate
concluding this is only a genetic factor in this
variety.
Rhyzopertha dominica feeding damage
10 adults/10 kernels/ 10 days
Sound Kernels
Degermed Kernels
Plodia interpunctella (Hubner)
Rhyzopertha dominica (F.)
Hypothesis We, therefore, tested the hypothesis t
hat seed coat factors, not the endosperm cause
feeding resistance to R. dominica and this
resistance is a genetic trait(s) not affected by
agronomic conditions.
R. dominica feeding damage on degermed kernels
Acknowledgments The authors acknowledge collabora
tion and helpful suggestions throughout the
project of L. Talbert, and S. Lanning who also
provided spring wheat samples P. Bruckner who
also provided winter wheat samples (Department
of Plant Sciences, Montana State
University-Bozeman). Financial support The
Anderson Foundation, Maumee Ohio (F. Dunkel,
P.I.) Montana Agricultural Experiment Station
(161) (F. Dunkel). This is a contribution to the
Multistate Project NC-213 Committee on
Management of Grain Quality and Security in
World Markets. Photo credits Clemson University
- USDA Cooperative Extension Slide Series,
www.insectimages.org
Results When subsamples of these varieties from t
he same locations and cultural conditions were
first subjected to a heavy infestation of P.
interpunctella and then to the same age adult R.
dominica, damage was significantly greater than
on sound kernels. We found varietal differences
within wheat class, differences that are genetic,
i.e. they superceded site and agronomic
conditions. Using our rapid, intensive feeding
bioassay and frass analysis we found no
significant difference, ANOVA with SNK means
comparison (SAS 1988), in resistance to R.
dominica, among sound kernels of hard red wheat,
comparing all locations and cultural conditions
(irrigated versus dryland production). However
predamaged kernels showed significant difference
in resistance. This collaborative damage caused
feeding damage by R. dominica to increase 2 to
7.5 fold, measured by R. dominica frass
production. We also found significant
differences among varieties in sensitivity to P.
interpunctella attack.
Materials and Methods Evaluated in hard spring
and winter wheat produced 2001, 2002 (Bozeman,
Conrad, Fort Benton, Havre, Huntley, Kalispell,
Moccasin, Sidney, Winifred, Montana).
All varieties except Penawawa (Montana Flours
and Grain, Ft. Benton) provided by Luther Talbert
and Phil Bruchner, Dept. of Plant Sciences
Montana State University. All varieties were
raised organically. Grain frozen on receipt (-20
C) 3 days, equilibrated to test conditions
(25.5 1C, 45 5 R.H., 1212 LD).
Each kernel inspected for damage. Only whole
sound kernels selected for experiments.
35g grain replicates, 4 reps/location/variety/agr
onomic condition, placed in a 230ml(½ pint) Mason
jar with fine brass mesh screen and filter paper
lid. Developed an intensive feeding bioassay a
nd frass analysis based on Hockensmith et al.
1986. Eggs collected from adult Indian mealmoth,
Plodia interpunctella (Hübner) (Lepidoptera
Pyralidae), used 0-24hr postoviposition. 88 eggs
placed on each of four replicates, lids replaced,
containers returned to incubator at test
conditions for 82 days (allowing minimum of a
second generation to develop).
After 82 days all samples frozen (-20C)3 days
then reequilibrated to test conditions.
Micro-weight analysis (Ohaus SC2020 balance
0.01g accuracy) of all frass and silk produced
by P. interpunctella growth and development,
statistically analyzed with SAS ANOVA (SAS
Institute 1988). From these replicates, kernel
s were evaluated and selected for degermed only
damage. These kernels had germ cover and germ
consumed by the moth larvae, with endosperm and
pericarp intact, untouched. These degermed
kernels became treatment class for R. dominica
experiments. For R. dominica experiments, 0-24
hr post emergence adults. 10 kernels per 5.5ml
minivial, three reps per treatment.
Controls whole sound kernels of each variety,
test treatments degermed kernels.
In each minivial, 10 adult R. dominica were
allowed to feed on 10 kernels for 10 days at test
conditions. Samples were then frozen to (-20C)
for 3 days then equilibrated to test
conditions3 days. Frass output measured with a
Sartorius BP121S balance (0.0001g accuracy) and
statistically analyzed with SAS ANOVA (SAS
Institute 1988).
Literature Cited Hockensmith, P. E., T. L. Devine
, D. E. Legg, and J. G. Rodriguez. 1986.
Energy consumption and food utilization of the
Indian meal moth (Lepidoptera Pyralidae) on
different corn genotypes. J. Kans. Entomol.
Soc. 59(4) 598-603. McGaughey, W. H., R. D. Spe
irs, and C. R. Martin. 1990. Susceptibility of
classes of wheat grown in the United States to
stored-grain insects. J. Econ. Entomol. 83
1122-1127. Rao, G. H. R., and D. A. Wilson. 1972
. Loss of weight from feeding of lesser grain
borer. J. Kans. Entomol. Soc. 45238-241.
SAS Institute. 1988. SAS technical report
P-179, additional SAS/STAT procedures, release
8.00. SAS Institute, Cary, N.C.
Sinha, R. N., C. J. Demianyk, and R. I. H.
McKinzie. 1988. Vulnerability of common wheat
cultivars to major stored-product beetles. Can.
J. Plant Sci. 68 337-343. Singh, O. P., and V.
S. Singh. 1995. Inheritance of resistance to
lesser grain borer, Rhyzopertha dominica in
wheat grain. Bull. Entomol. 3663-71.
Toews, M. D., G. W. Cuperus, and T. W. Phillips.
2000. Susceptibility of eight U.S. wheat
cultivars to infestation by Rhyzopertha dominica
(Coleoptera Bostrichidae). Environ. Entomol.
29250-255. Watts, V., and F.V. Dunkel. 2003.
Postharvest resistance in hard spring and winter
wheat varieties of the northern great plains to
the Lesser Grain Borer (Coleoptera
Bostrichidae). J. Econ Entomol. 96(1)
220-230. Yetter, M. A., R. M. Saunders, and H. P.
Boles. 1979. a-Amylase inhibitors from wheat
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Plodia interpunctella feeding damage
Hard Red Spring Wheat
A
A
Mean frass and silk produced (mg)
B
C
C
C
C
C
C
Montana 2002, 88 eggs on 35g, 82 daMeans
followed by same letter do not differ
significantly (P0.05 Student-Newman-Kuels
comparisons).
Hard Red Winter Wheat
A
A
Mean frass and silk produced (mg)
A
A
B
C
C
C
Montana 2001, 88 eggs on 35g, 82days Means
followed by same letter do not differ
significantly (P0.05 Student-Newman-Kuels
comparisons).