October 15, 2012

Key soybean cyst nematode findings in ‘Nature’

by Andrea Hahn

CARBONDALE, Ill. -- A team of scientists, including several from Southern Illinois University Carbondale, may have unlocked the mystery of why some soybeans are resistant to the devastating soybean cyst nematode.

Scientists, led by Khalid Meksem, professor of plant, soil, and agricultural systems at SIU Carbondale, and Melissa G. Mitchum, associate professor of plant sciences at the University of Missouri, have been studying the problem for years.

And they may have found an answer within the soybean itself.

This week, the prestigious international journal "Nature," publishes research results in which the researchers identify a soybean cyst nematode resistant gene that gives certain soybeans natural resistance. The study further examines the underlying processes that help the plants ward off pathogens. The team hopes that better understanding of how the resistant genes work will lead to better pest resistance and improved crop yield.

The scientists still have their work cut out for them, as they learn more about how the identified gene works.

The paper detailing the work and results of the research teams, "A Soybean Cyst Nematode Resistance Gene Points to a New Mechanism of Plant Resistance to Pathogens," appear online in "Nature" today (Oct. 15).

Meksem said "Nature" is widely considered the top scientific journal, especially as far as its impact on the international scientific community and the public, as well. Publication in "Nature" is a career highlight for any scientist, often a once-in-a-lifetime occurrence, Meksem said. This is the first time "Nature" has published a paper from the SIU Carbondale College of Agricultural Sciences.

Other SIU Carbondale researchers include: Shiming Liu, Aziz Jamai, and Tarik El-Mellouki, who were graduate and post-doctoral students while they were part of the research team.

The soybean cyst nematode seems like something out of a science-fiction movie. The microscopic worm attacks the root system of a soybean plant, leading to stunted root and shoot growth, and then in dead roots and loss in seed yield.

The female nematode swells as she devours the root system of the soybean plants, often bursting through the root and becoming visible to the naked eyed. She lays 200 to 400 eggs, forming an egg sac inside of herself. She dies then, and becomes a hard cyst. The eggs hatch, the larvae develop inside the cyst, and then break into the root system to begin the cycle again.

It's a lifecycle that devastates soybean crops the world over, costing farmers in the United States alone more than $1 billion in lost crop yield every year. Farmers and scientists have long known that some soybeans are resistant to the cyst nematode, but exactly why remained a mystery.

In the past, farmers used the soybean cyst nematode resistant soybeans, and they practiced crop rotation to keep the nematodes in check. An infected field can lose as much as 75 percent of its yield -- a devastating loss to an individual farmer, and a serious challenge to the multi-billion dollar soybean industry.

Now that the gene is identified, plant breeders know which gene to emphasize in breeding resistant varieties of soybean. This discovery comes at a time when farmers desperately need new solutions, as the nematodes adapt and find ways through the soybeans' defenses.

"We realized we had the gene about two years ago," Meksem said, noting that the University of Missouri team worked closely with them to determine how the gene worked -- an ongoing part of the research.