Cowpea Plants React to Insect Attack
June 14, 2007
Cowpea plants can indirectly perceive
attack from fall armyworms by detecting and responding to degradation products
of their own tissuesthe first time this ability has been observed in
plants, according to Agricultural Research Service (ARS) scientists in Gainesville, Fla. The
scientists hope to capitalize on this discovery by finding a way to intensify
this defense response, thus boosting a plant's ability to protect itself.
Previous studies have shown that plants have the ability to indirectly
perceive pathogen attacks and protect themselves against these microbes. But
this is the first time such a plant defense mechanism has been seen in response
to insect attacks. The findings are reported in the June issue of Plant Physiology.
The indirect perception of insects means the plant doesn't recognize the
pests directly. Instead, the plant perceives abnormal digestive protein
fragments of itselfproduced by insect digestionas an insect attack.
This begins a series of biochemical responses geared to preventing further
Armyworms are a group of related caterpillars that defoliate a wide range of
crop plants. Plant physiologist
Schmelz and colleagues at the
Center for Medical, Agricultural and Veterinary Entomology's
Research Unit isolated and identified a small peptide, called inceptin,
from the oral secretions of fall armyworm (Spodoptera frugiperda)
In cowpea plants (Vigna unguiculata)also known as blackeyed
peasthis peptide triggers the production of ethylene and a series of
other defense-related phytohormones. In lab studies, only fall armyworm
larvae that produced inceptins significantly induced cowpea defenses.
Plants can perceive and defensively respond to attack either directly, by
impeding pest growth, or indirectly, by promoting advantageous interactions
with beneficial organisms.
In 2005, the United States produced almost 23,000 tons of cowpeas.
Worldwide, cowpeas rank among the top five food fiber crops because they can
tolerate poor, dry soils.
ARS is the U.S. Department of
Agriculture's chief scientific research agency.