Sunday, July 29, 2007

Climate change will increase pest attacks on soybeans

Scitizen: Elevated [CO2] increased the susceptibility of soybean to invasive insects by down-regulating the expression of genes related with hormonal defense, which down-regulate important antidigestive defenses against beetles.

During the last annual meeting of the American Society of Plant Biologists in Chicago (July 7-11, 2007), scientists Jorge A. Zavala, Clare L. Casteel, May R. Berenbaum and Evan H. De Lucia from the University of Illinois, USA have shown that elevated CO2 may negatively impact the relationship between some plants and insects. CO2 is one of the most important gases involved in global warming, the greenhouse effect. However, not only temperature, but also CO2 concentrations itself can affect ecosystem functions, including plant-insect interactions.

By 2050, soybean (Glycine max) the world’s most widely grown seed legume will grow in an atmosphere with a 50% higher carbon dioxide concentration ([CO2]) and could affect plant-insect interactions. Insect’s attack produces high economic costs to field crops. Soybeans respond to insect attack by producing defense compounds that inhibit digestive enzymes (proteinases) in the gut of insects, reducing their performance and crop damage. The production of this antidigestive compounds are regulated in plants by the hormone jasmonic acid (JA). However, elevated [CO2] levels disrupt this equilibrium in plant-insect interactions and benefit the herbivore.

This study, supported by the Department of Energy, Office of Science, found that when soybeans were exposed to elevated [CO2] the crop became more susceptible to Japanese beetle (Popillia japonica) colonization, producing more leaf damage. …

“Our results suggest that elevated [CO2] increased the susceptibility of soybean to invasive insects by down-regulating the expression of hormones related with defense, which down-regulate important defense compunds against beetles,” Zavala said.

Zavala also explained, “Under natural field conditions, elevated [CO2] not only increased susceptibility of soybean to herbivory by the invasive species Japanese beetle, but also enhanced the performance of these beetles.”…

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