Soybean varieties that are resistant to the soybean cyst nematode (SCN) are an extremely important tool for farmers to use to manage this damaging pest. In general, SCN-resistant soybean varieties yield greater than susceptible varieties planted in SCN-infested fields, says Greg Tylka, Iowa State University Extension nematologist. And the SCN-resistant varieties keep SCN population densities from increasing, which ensures profitable soybean production in future years.
With soybean checkoff funding from the Iowa Soybean Association, ISU has updated their annual list of SCN-resistant soybean varieties and published it as Soybean Cyst Nematode-Resistant Soybean Varieties for Iowa, PM 1649. There is information in the publication about more than 800 SCN-resistant soybean varieties from 45 different seed companies and three universities.
ISU advises planting varieties with varying sources of SCN resistance
The publication was compiled in October 2010 and lists information on pure varieties, but not blends or mixtures of varieties, says Tylka. Information about the varieties includes relative maturity, herbicide resistance, iron deficiency chlorosis tolerance and source of SCN resistance. ISU recommends growing soybean varieties with varying sources of SCN resistance in a rotation, if possible, to maintain effectiveness of the different sources of resistance. The publication can be downloaded from the ISU Extension Online Store.
The 813 SCN-resistant varieties listed in the 2010 version of the publication are the most ever included in the publication (see figure below). However, almost all of the SCN-resistant varieties in the publication have resistance from the breeding line PI88788, notes Tylka. Less than 2% of the varieties in the 2010 list have a specific source of SCN resistance other than PI88788, including 13 varieties with the Peking source of SCN resistance - three in maturity group 1 and ten in maturity group 2. The number of SCN-resistant soybean varieties with a specific source of SCN resistance other than PI88788 has decreased markedly from a high of 15% in 2004 (see figure below).
There are 21 SCN-resistant soybean varieties in the publication that were developed by ISU scientists, all with soybean checkoff funding from the Iowa Soybean Association, Tylka points out. Two of the varieties contain sources of SCN resistance that have not been used in varieties in the list before. Variety "IAR2101 SCN" (maturity group 2) has SCN resistance from PI88788 in combination with PI507354. And variety "IAR3001 Phyto SCN" (maturity group 3) has SCN resistance from PI438489B and PI90363.
ISU has management recommendations for SCN available online in a downloadable format, Soybean Cyst Nematode (SCN) Management Recommendations, IPM 63. Additional information about the biology, scouting and management of SCN can be found at www.soybeancystnematode.info.Number of SCN-resistant soybean varieties available to Iowa soybean growers 1991 to 2010.