Rhizobia Confers Aphid Resistance in Soybean

Soybean aphids are one of the biggest problems for farmers in the US. The pest costs soybean growers more than USD 500 million annually in lost crop yields and spraying costs. Aphid infestation was first reported in Wisconsin in 2001 and has since been recorded in 21 US states and three Canadian provinces. Soybean aphids cause damage by sucking plant sap. They can also transmit viruses, such as the dreaded soybean and alfalfa mosaic virus. Farmers normally apply pesticides to control aphid populations. Recently, researchers at the Pennsylvania State University have discovered another way of controlling the pesky sap-suckers: using nitrogen-fixing bacteria.

Legumes have the ability to fix atmospheric nitrogen, thanks to symbiotic bacteria called rhizobia. The Penn State researchers found out that plant–rhizobia interactions influence plant resistance to insect herbivores, such as soybean aphids, and that some rhizobia strains confer greater resistance to their mutualist partners than do others.

"This is the first time anyone has shown how different strains of rhizobia can effect herbivory," said Consuelo De Moraes, lead author of the paper published in the journal Plant and Soil. "This may be another tool to use to protect plants from insect herbivory. It may also be applicable to other legumes." The scientists are yet to identify what rhizobia do to ward off soybean aphids.

For the complete article, read http://live.psu.edu/story/39092 The paper published by Plant and Soil is available at http://dx.doi.org/10.1007/s11104-009-9924-1