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New strategies for defense against Hessian fly
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By Beth Forbes, Coordinator
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No larger than a pencil point, this shaft of wheat grown in a Purdue greenhouse is infested with Hessian fly larvae.
The darker puparium is an advanced stage of the larva, from which an adult fly (inset) will emerge. |
Wheat has ways to battle the tiny, red wormlike insects that nibble on leaves and destroy crops worldwide, but the Hessian fly larvae that survive eventually evolve methods to overcome plant defenses.
“The larvae probe the plant to open a sustained feeding site,” says Purdue University entomologist Jonathan Neal. “Resistant plants block the larvae from establishing a feeding site. It’s as if larvae keep trying to open doors because they are programmed to look for a feeding site. In resistant plants, the doors are all locked. Then the larvae finally crawl down to the base of the plant and die. This is death by frustration.”
However, some larvae are able to thwart this process and force the plant to establish a feeding site. Purdue and U.S. Department of Agriculture-Agriculture Research Service (USDA-ARS) scientists have identified Hessian fly genes that nullify the toxins that wheat produces to protect itself from the munching larvae. “We’re trying to understand how the insect overcomes plant resistance and use that basic knowledge to enhance the durability of wheat against Hessian fly attack by combining several genes for resistance or other strategies,” says USDA-ARS entomologist Richard Shukle.
While the insects can’t establish feeding sites on resistant plants, the larvae can alter the physiology and change the level of certain proteins in susceptible plants. This forces the plant to feed the larvae.
The research will help scientists understand the complexity of antioxidant defense responses during interaction between Hessian flies and wheat, he says. It may also be applicable to other pest-plant encounters.
Photo credit: Tom Campbell
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