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New Method Tests Natural Toxins to Help Wheat Battle Pest

Wheat (USDA.gov)

(USDA.gov)

A research team from Purdue University in Indiana and U.S. Department of Agriculture have devised a method of finding natural toxins to build wheat’s resistance to an insect pest. The researchers’ results appear online in advance of publication in the Journal of Insect Physiology (paid subscription required).

Larvae from the Hessian fly attack and feed off wheat — just the larvae, not adults — and have been a scourge of wheat growers in the U.S. since the 18th century. The fly larvae secrete a substance on the plants that creates a groove on the plant tissue, opening it up for the larvae to feed. The larvae then feed by using their mouth parts like sandpaper on the leaf surface and sucking up plant juices that seep out.

Efforts to build genetic resistance to this pest in wheat have not proved successful, which led the researchers from Purdue and USDA’s Agricultural Research Service to try a different approach. That new approach was to find plants that successfully resist the Hessian fly and develop a method to test toxins from these other plants on Hessian fly larvae.

The only way the Hessian fly larvae feed, however, is on actual wheat plants, not in lab-based simulations. Developing a transgenic wheat for these tests would be a long, arduous task with no guarantee of success.

The researchers instead devised a testing method that simulates the effect of a transgenic plant without the lengthy and costly procedures necessary to actually create those plants. To get the toxins into the fly larvae, the scientists allowed Hessian flies to lay eggs on the leaves of seedling wheat plants.

When the eggs hatched, the researchers took the plants from the soil, cleaned and trimmed their roots, and replanted the seedlings as hydroponics with the toxic proteins added to the plants’ water. When the fly larvae attacked and fed as usual, they were also ingesting the toxins that were taken up through the water. Protein immunoblot detection tests, which use antibodies to detect the presence of a particular protein, showed that the larvae had ingested the toxins added to the water.

“The plant is just acting like a big straw taking up the toxins,” says USDA’s Christie Williams. “It’s just like putting a carnation into a cup of colored water and watching the flower change colors.”

The team tested nine lectins, which are anti-nutrient proteins that disrupt digestive function. The Hessian fly larvae responded most positively to snowdrop lectin, which comes from snowdrop bulbs, a type of flowering plant.

The researchers report that larvae that ingested the snowdrop lectin developed only half as fast as the control larvae. They also reported evidence of disruption of the larvae’s digestive systems and metabolism.

Read more: International Consortium Sequences Wheat Pathogen Genome

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