Second soy nematode resistance option on deck for 2012

A soybean variety offering resistance to a “different race spectrum” of soybean cyst nematode (SCN) has picked up Canadian registration for a 2012 launch.

Syngenta Seeds Canada on Monday announced the approval for S14-M4, an NK Brand Genuity Roundup Ready 2 Yield variety which the company said will be the first in Canada to include Peking resistance to the crop pest.

According to Syngenta Seeds Canada’s breeding project lead for soybeans, Don McClure, the SCN-resistant varieties available so far for use in Canada get their resistance from another soybean breeding line, PI88788.

“With S14-M4, growers (will) have another source of resistance against a different race spectrum of soybean cyst nematode,” McClure said. “If only one source of protection is relied on, then the pest will overcome resistance over time.”

SCNs are microscopic-scale threadlike worms that burrow into a soybean plant’s root system to draw nutrients from the plant.

Infestations can cause plant stress, suppress root and shoot growth and impact yields, Arva, Ont.-based Syngenta Seeds said in its release Monday.

As Iowa State University (ISU) Extension explains on its SCN page, the PI88788 lines are resistant to SCN races 3, 6, 8, 9, 10, 12, 13, and 14, while Peking varieties are resistant to SCN races 1, 3, 5, 6, 7, 8, 10, and 15.

Rotating resistance

But it’s not absolutely necessary to have a “perfect match” of SCN race to SCN-resistant soybean variety, ISU Extension said.

For example, a PI88788 soybean plant, while not resistant to SCN race No. 7, should still suppress the No. 7 race’s population in a field, enough for crop yields to get ahead and prevent a buildup of SCN, ISU said.

While Peking varieties and PI88788 varieties are both available already in the U.S., ISU has said it will no longer perform SCN “race testing” to match a field’s infestation to a resistant variety.

“Instead, we advocate using well-adapted SCN-resistant varieties in infested fields, taking care to rotate different sources of SCN resistance periodically, and closely monitoring SCN population densities in infested fields.”

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