Impact of Elevated Levels of Atmospheric CO
2
and Herbivory on Flavonoids of Soybean
(Glycine max Linnaeus)
Bridget F. O’Neill
&
Arthur R. Zangerl
&
Orla Dermody
&
Damla D. Bilgin
&
Clare L. Casteel
&
Jorge A. Zavala
&
Evan H. DeLucia
&
May R. Berenbaum
Received: 2 February 2009 / Revised: 10 August 2009 /Accepted: 21 August 2009 /Published online: 14 January 2010
#
Springer Science+Business Media, LLC 2010
Abstract Atmospheric levels of carbon dioxide (CO
2
)
have been increasing steadily over the last century. Plants
grown under elevated CO
2
conditions experience physio-
logical changes, particularly in phytochemical content, that
can influence their suitability as food for insects. Flavo-
noids are important plant defense compounds and antiox-
idants that can have a large effect on leaf palatability and
herbivore longevity. In this study, flavonoid content was
examined in foliage of soybean (Glycine max Linnaeus)
grown under ambient and elevated levels of CO
2
and
subjected to damage by herbivores in three feeding guilds:
leaf skeletonizer (Popillia japonica Newman), leaf chewer
(Vanessa cardui Linnaeus), and phloem feeder (Aphis
glycines Matsumura). Flavonoid content also was examined
in foliage of soybean grown under ambient and elevated
levels of O
3
and subjected to damage by the leaf
skeletonizer P. japonica. The presence of the isoflavones
genistein and daidzein and the flavonols quercetin and
kaempferol was confirmed in all plants examined, as were
their glycosides. All compounds significantly increased in
concentration as the growing season progressed. Concen-
trations of quercetin glycosides were higher in plants grown
under elevated levels of CO
2
. The majority of compounds
in foliage were induced in response to leaf skeletonization
damage but remained unchanged in response to non-
skeletonizing feeding or phloem-feeding. Most compounds
increased in concentration in plants grown under elevated
levels of O
3
. Insects feeding on G. max foliage growing
under elevated levels of CO
2
may derive additional
antioxidant benefits from their host plants as a consequence
of the change in ratios of flavonoid classes. This nutritional
benefit could lead to increased herbivore longevity and
increased damage to soybean (and perhaps other crop
plants) in the future.
Keywords Flavonol
.
Isoflavone
.
Popillia japonica
.
Aphis glycines
.
Vanessa cardui
.
Global climate change
.
Plant-insect interactions
Introduction
Atmospheric carbon dioxide (CO
2
) levels have risen
steadily since the start of the Industrial Revolution, from
B. F. O’Neill
:
A. R. Zangerl
:
M. R. Berenbaum (*)
Urbana-Champaign, Department of Entomology,
University of Illinois,
320 Morrill Hall, 505 S. Goodwin Avenue,
Urbana, IL 61801, USA
e-mail: maybe@uiuc.edu
O. Dermody
Pioneer Hi-Bred Switzerland S.A.,
DuPont Agriculture and Nutrition,
Via Cantonale/Galleria 3B,
CH-6928 Manno, Switzerland
D. D. Bilgin
:
E. H. DeLucia
:
M. R. Berenbaum
Urbana-Champaign, Institute for Genomic Biology,
University of Illinois,
1206 West Gregory Drive,
Urbana, IL 61801, USA
C. L. Casteel
:
E. H. DeLucia
Urbana-Champaign, Department of Plant Biology,
University of Illinois,
265 Morrill Hall, 505 S. Goodwin Avenue,
Urbana, IL 61801, USA
J. A. Zavala
Consejo Nacional de Investigaciones Cientificas y Technicas,
Catedra de Bioquimica, Facultad de Agronomia,
University of Buenos Aires,
Avenida San Martin 4453,
Buenos Aires, Argentina
J Chem Ecol (2010) 36:35–45
DOI 10.1007/s10886-009-9727-0