Nematode Resistant Soybeans
A soybean pest responsible for an estimated $
1.4 billion dollars in U.S. crop losses each year will soon go hungry, thanks to Purdue University research. A technology offering complete resistance to soybean cyst nematode, developed by a team of Purdue scientists and their colleagues at the Indiana Crop Improvement Association, consistently produced higher soybean yields than conventional nematode-resistant varieties in a series of field trials completed last fall. The technology, which employs a unique combination of genes known commercially as CystX®, will be widely available for planting during the 2005 season. CystX® is not a seed variety, but is instead a suite of genes that can be bred into already existing soybean varieties. "This year's field trials clearly demonstrate that this technology does work," said Virginia Ferris, Purdue entomologist and one of the scientists who developed the CystX® technology. "CystX® is a major improvement over the existing methods for soybean management. It offers higher yields and resistance to all varieties of soybean cyst nematode, even when the nematodes are present in high densities."
Soybean cyst nematode is a tiny parasitic worm found in up to 60 million acres of cropland in all U.S. soybean-growing regions. In its juvenile stage, the worm feeds on the roots of soybean plants, severely limiting the plant's ability to produce pods. In field trials, CystX® soybeans produced an average of 5.4 bushels per acre more than conventional varieties resistant to soybean cyst nematode. At a soybean price of $5 per bushel, this could put $27 more in farmers' pockets for every acre of soybeans they plant if the cost of CystX® varieties is the same as conventional seed. Fields planted with CystX® varieties also had up to a 75 percent reduction in soybean cyst nematode population densities. Since most of the current resistant soybean varieties can only fend off one or two of the known 16 races, the nematode is especially problematic to manage in mixed race fields.
Ferris and her colleagues developed the CystX® technology through conventional breeding methods with molecular markers that brought together a combination of genes providing resistance to all soybean cyst nematode field populations. The resistance genes originated in the Hartwig soybean, but resistant Hartwig has yield problems and cannot be easily crossed with high-yielding varieties, Ferris said. The CystX® technology overcomes this yield loss thanks to a unique group of genes called pairing control genes, which permit the resistance genes to be crossed with high-yielding lines. Breeders rely on these pairing control genes to ensure that soybean varieties carrying the CystX® technology include the full suite of soybean cyst nematode resistance genes as well as genes that lead to higher yields. (Ag Answers, 22/15/05).
