Breaking a paradigm: male-produced aggregation pheromone for the Colorado potato beetle
Joseph C. Dickens1,*,
James E. Oliver2,
Benedict Hollister1,*,
John C. Davis1,* and
Jerome A. Klun2
1 United States Department of Agriculture, Agricultural Research Service,
Plant Sciences Institute, Vegetable Laboratory, Beltsville, MD 20705,
USA
2 United States Department of Agriculture, Agricultural Research Service,
Plant Sciences Institute, Chemicals Affecting Insect Behavior Laboratory,
Beltsville, MD 20705, USA
* Present address: United States Department of Agriculture, Agricultural
Research Service, Plant Sciences Institute, Chemicals Affecting Insect
Behavior Laboratory, Beltsville, MD 20705, USA
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Fig. 1. Gas chromatographs (FID) with coupled electroantennograms (EAD) from
Colorado potato beetles in response to volatiles emitted over a 3 h test
period by an undamaged potato plant (A), a mechanically damaged potato plant
(B), 10 female beetles feeding on a potato plant (C) and 10 male beetles
feeding on a potato plant (D). EADs in A, C and D were recorded from female
antennae; the EAD in B was recorded from a male antenna. A, nonanal;
B, 2-phenyl ethanol; CPB I, male-specific compound; IS, internal
standard (10 ng of decane); Sesquiterpene region, retention times of various
sesquiterpenes. No differences were observed between EADs of male and female
antennae.
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Fig. 2. Production of the male-specific compound (24h collection) CPB I by 20
untreated male Colorado potato beetles (N=4) (A) and enhancement of
CPB I production by experimental treatments (1 µl injection into the gas
chromatograph of 50 µl of rinse): (B) topical treatment with 10 µg of
juvenile hormone III (JH III) (N=4); (C) antennectomy (N=3);
and (D) combined treatment of topical application of JH III and antennectomy
(N=3). CPB I, male-specific compound; P, 6-methyl-5-hepten-2-one;
FID, response of flame ionization detector. The electroantennogram (EAD)
response is included for A—C. EADs in A and B were recorded from female
antennae; the EAD in C was recorded from a male antenna. No differences were
observed in EADs of male and female antennae. SR, sesquiterpene region.
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Fig. 3. Structure of the Colorado potato beetle male-specific compound
(S)3,7-dimethyl-2-oxo-oct-6-ene-1,3-diol (A) (compound 1, CPB I) and
the related compound 6-methyl-5-heptene-2-one (B) (compound 2, P).
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Fig. 4. Mean electroantennogram responses (in mV) from Colorado potato beetles
elicited by a 10ng injection of (S)-enantiomer,
(R)-enantiomer and racemic CPB I. Responses of males and females were
not significantly different and were therefore combined. Values are means
± S.E.M. (N=6, three males and three females). Columns with
different letters are significantly different, P<0.01, Duncan's
multiple-range test.
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Fig. 5. Behavioral responses (percentage of choices) in an open Y-track
olfactometer of male (A) and female (B) Colorado potato beetles to volatiles
emanating from serial source loads of (S)-CPB
I=(S)-enantiomer, (R)-CPB I=(R)-enantiomer and
racemic CPB I=Racemate versus solvent control. Each individual was
tested only once. Shaded columns represent responses to experimental
treatment; open columns represent responses to the solvent control. Asterisks
indicate that the response to an experimental treatment differs significantly
from the control (**P<0.01) by testing the hypothesis
that the binomial proportion is significantly different from P=0.05
using the standard normal approximation
(Brase and Brase, 1983 ). Values
are percentages of 20 beetles responding to each treatment ±
S.E.M..
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© The Company of Biologists Ltd 2002
