UGA scientists engineer root-knot nematode resistance

Athens, Ga. – University of Georgia professor Richard Hussey has spent 20 years studying a worm-shaped parasite too small to see without a microscope. His discovery is vastly bigger. Hussey and his research team have found a way to halt the damage caused by one of the world's most destructive groups of plant pathogens.

Root-knot nematodes are the most economically important group of plant-parasitic nematodes worldwide, said Hussey, a distinguished research professor in plant pathology at the UGA College of Agricultural and Environmental Sciences.

They attack nearly every food and fiber crop grown, about 2,000 plant species in all.

The nematode invades plant roots, and by feeding on the roots' cells, they cause the roots to grow large galls, or knots, damaging the crop and reducing its yields.

Working with assistant research scientist Guozhong Huang and research technician Rex Allen, Hussey discovered how to make plants resistant to root-knot nematode infection.

Eric Davis at North Carolina State University and Thomas Baum at Iowa State University also collaborated on the research.

The discovery "has the potential to revolutionize root-knot resistance in all crops," Hussey said.

The most cost-effective and sustainable management tactic for preventing root-knot nematode damage and reducing growers' losses, he said, is to develop resistant plants that prevent the nematode from feeding on the roots. Because root-knot nematode resistance doesn't come naturally in most crops, Hussey's group bioengineered their own.

The results of the study were published Sept. 26 in the journal, Proceedings of the National Academy of Sciences.

Four common root-knot nematode species account for 95 percent of all infestations in agricultural land. By discovering a root-knot nematode parasitism gene that's essential for the nematode to infect crops, the scientists have developed a resistance gene effective against all four species.

Using a technique called RNA interference, the researchers have effectively turned the nematode's biology against itself. They genetically modified Arabidopsis, a model plant, to produce double-stranded RNA to knock out the specific parasitism gene in the nematode when it feeds on the plant roots.

This knocked out the parasitism gene in the nematode and disrupted its ability to infect plants.

"No natural root-knot resistance gene has this effective range of root-knot nematode resistance," Hussey said.

The researchers' efforts have been directed primarily at understanding the molecular tools the nematode uses to infect plants. This is a prerequisite for bioengineering durable resistance to these nematodes in crop plants.

Through this research, they've discovered the parasitism genes that make a nematode a plant parasite so it can attack and feed on crops, Huang said.

"Our results of in-plant RNA interference silencing of a parasitism gene in root-knot nematodes provides a way to develop crops with broad resistance to this destructive pathogen," Hussey said. "Equally important, our approach makes available a strategy for developing root-knot-nematode-resistant crops for which natural resistance genes do not exist."

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Funding for the project came from the U.S. Department of Agriculture's Cooperative State Research, Education and Extension Service National Research Initiative and the UGA College of Agricultural and Environmental Sciences.


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