URBANA - This year farmers in the Midwest are growing a new variety of soybeans developed by University of Illinois researchers that has resistance to soybean aphids. However, in addition to the resistant plants, U of I researchers also discovered a new soybean aphid which is not controlled by this resistance.
Soybean aphids made their first appearance in North America in the summer of 2000, resulting in tremendous crop losses for farmers. U of I researchers began immediately searching for a variety of soybean that is resistant to the new pest.
Dowling and Jackson were the first two resistant varieties to be identified. "We have the U. S. Soybean Germplasm collection here at Illinois. It houses about 18,000 different accessions," said Glen Hartman, soybean plant pathologist with the USDA and U of I. "We didn't screen all 18,000, but we went through a small set of 4,000 to 5,000 and that's where Jackson and Dowling came from. We knew they were resistant, but we had to do the crossings and look at the inheritance patterns to figure out whether the resistance was because of a single gene or multiple genes."
With additional screening, a third soybean resistant to aphids was found -- a Japanese variety known as PI 200538. "After we mapped the genes from these sources, we discovered that Jackson and Dowling had genes mapping to the same place on a chromosome and the PI had a gene mapping to a different place. This means that Jackson and Dowling likely have the same resistance gene and PI 200538 has a different gene we can use in breeding."
Diers said that both Jackson and Dowling originated in the southern United States, so neither could be grown to seed in the Midwest. They used traditional breeding techniques together with marker-assisted selection to quickly breed the resistance genes into varieties that are adapted to the Midwest.
"Because the aphid resistance is conferred by a single gene in the resistance sources, we
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University of Illinois at Urbana-Champaign