Scientists have identified a soybean gene responsible for making some varieties resistant to the cyst nematode, a pest responsible for $1 billion in annual crop losses.
The gene wards off nematodes by making an enzyme that starves the pest or acts as a natural pesticide, according to a paper released today in the journal Nature. The study is the first to identify the gene and its mechanism for creating resistance, said lead authors Melissa Mitchum of the University of Missouri in Columbia and Khalid Meksem of Southern Illinois University in Carbondale.
The soybean cyst nematode can cut crop yields 50 percent and cause $1 billion in losses in the $42.2 billion annual U.S. crop, making it the top soybean pathogen, Greg Tylka, a plant pathology professor at Iowa State University. Knowing which gene is responsible for natural resistance will help breeders identify the hardiest varieties and could lead to genetically modified soybeans with complete resistance, he said.
“This could speed up breeding for soybean cyst nematode resistance by a quantum leap,” Tylka, who wasn’t involved with the Nature study, said today by telephone from Ames, Iowa. “It will allow traditional breeding to be very precise.”
The soybean cyst nematode starts life as a microscopic worm that burrows into soybean roots, where the female feeds and swells into a leathery, lemon-sized cyst full of eggs. The eggs are “time released,” hatching over the course of a decade or more, so rotation with other crops does little to eradicate the pests from a field, Tylka said.
Soybeans have been bred to resist the cyst nematode, an import from Asia, since it was first discovered in the U.S. in 1954, Tylka said. Resistant varieties remain imperfect, with damage occurring to varying degrees depending on the plant and the type of cyst nematode in the field, he said.
Identification of a second soybean gene for cyst nematode resistance is needed before plants can be created that offer complete resistance, Tylka said. In the near term, researchers may want to focus on how the newly discovered enzyme-producing gene confers resistance.
In addition to breeding soybeans for resistance to nematodes, Monsanto Co. (MON), the world’s biggest seed company, has an early-stage research project on a bean that is genetically modified to resist the pest, Sara E. Miller, a spokeswoman for the St. Louis-based company, said in an e-mail. Monsanto, which in 2008 made public its sequence of the soybean cyst nematode genome, also is developing a seed treatment to control nematodes, she said.
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