WEST LAFAYETTE, Ind. — Purdue University and University of
Illinois researchers have discovered a novel corn mutant whose leaves are highly
susceptible to attack by Western corn rootworm beetles, a pest that feeds
primarily on corn silks and pollen.
While Western corn rootworm beetles were previously thought
to avoid corn leaves based on food-source preference, study of the mutant
suggests that normal corn plants have an active defense mechanism that deters
the beetles from feeding on their foliage.
Identifying this mechanism could lead to new strategies for
controlling Western corn rootworm, which is the most destructive insect pest of
corn in the U.S.
“This opens up a whole new opportunity to understand more
about the mechanism of defense in corn to control this beetle,” said Gurmukh
Johal, professor of botany and plant pathology.
Johal and Stephen Moose of Illinois independently discovered
the mutant around the same time.
“In identifying the genetic pathway involved in resistance,
we can develop better ways of controlling this pest without having to use
insecticides,” Johal said.
Western corn rootworm causes more than $1 billion damage a
year in yield losses and control costs in the U.S., earning it the nickname “the
billion-dollar bug.” The rootworm larvae chew on the roots of corn plants while
the adult beetles eat the silks and pollen.
Current control measures include crop rotation, transgenic
corn plants and insecticides. But a rise in continuous corn systems, increased
rootworm resistance to transgenic plants and changes in rootworm behavior have
rendered these management strategies less effective.
Because the leaves of the corn mutant are singularly
attractive to Western corn rootworm beetles, the mutant could be used in a
“push-pull” pest-management strategy — luring the beetles to a specific location
where they can be controlled, said Christian Krupke, assistant professor of
entomology and co-author of the study.
“Once you can get them where you want, you can use
efficient, cost-effective ways of controlling them, either by directly targeting
and eliminating them or by keeping them away from your main crop,” he
In the absence of the beetle, the mutant is virtually
indistinguishable from normal corn plants, which may be why it was not
discovered earlier, said Johal.
Its leaves do not become vulnerable to attack by rootworm
beetles until it reaches the vegetative stage, about five to six weeks into the
On finding the mutant, Western corn rootworm beetles scrape
away the leaf tissue from the upper epidermis, resulting in a transparent
“window pane” appearance. If the beetle infestation is severe, the plants can
become completely defoliated, which also can reduce grain yield.
A combination of structural and biochemical changes in the
mutant leaves make them particularly vulnerable to attack. The cellular lobes
that interlock to provide structural strength are smaller and weaker in the
The leaves also have substantially reduced levels of
hydroxycinnmates and lignin, compounds that are responsible for cross-linking
microfibers in cell walls.
Further research is being done on the possibility of using
the mutant in pest control strategies and identifying the genetic pathway in
normal corn plants that prevents Western corn rootworm beetles from consuming
their leaves. The genes could be used to make corn plants more pest-resistant,
The paper was published online in PLoS ONE and is available
Funding for the research was provided by Pioneer, the U.S.
Department of Agriculture and the Illinois Agricultural Experiment Station.