By Greg Tylka, Department of Plant Pathology and Microbiology
Since 1990 the Iowa State University SCN-resistant Soybean Variety Trial Program has evaluated the agronomic performance and nematode control provided by hundreds of soybean varieties advertised as resistant to the soybean cyst nematode (SCN). The work is funded by the soybean checkoff through a grant from the Iowa Soybean Association.
The SCN-resistant varieties are grown in four replicate plots in each of three experiments conducted across one of three districts (northern, central and southern Iowa) each year. The experiments also include a few SCN-susceptible soybean varieties as “checks.” The locations of the experiments conducted in 2013 are shown in figure 1.
Figure 1. Locations of ISU SCN-resistant Soybean Variety Trial Program experiments in 2013.
Varieties also evaluated for iron deficiency chlorosis tolerance
Soybean checkoff-funded ISU research in the 1990s revealed a consistent, positive relationship between SCN population densities (numbers) and soil pH in Iowa. Greater numbers of SCN occur in fields or areas of a field with higher soil pH. And iron deficiency chlorosis (IDC) becomes a problem when soil pH is greater than 7.0. Consequently, many Iowa soybean farmers need to grow high-yielding soybean varieties that tolerate iron deficiency chlorosis as well as have resistance to SCN.
The ISU SCN-resistant Soybean Variety Trial Program evaluates the varieties for tolerance to IDC in experiments that are separate from those in which agronomic performance and SCN control of the varieties are assessed. Results of the IDC tolerance evaluations are included in the results of the experiments.
Individual location results available now online; complete report coming in January 2014
Results of most of the individual experiments conducted in 2013 are currently available online at www.isuscntrials.info. The complete, printed annual report of the 2013 results will be distributed in the Jan. 18, 2014, issue of Iowa Farmer Today.
More information about managing SCN
Iowa State University’s management recommendations for SCN are available online in a downloadable format, Soybean Cyst Nematode (SCN) Management Recommendations, IPM 63. An annually updated list of SCN-resistant soybean varieties for 2014 is available in PDF format online at the Iowa State University Extension and Outreach Online Store. For more information about the biology and management of SCN, visit www.soybeancyst.info and www.planthealth.info/scn_basics.htm.
Greg Tylka is a professor with extension and research responsibilities in management of plant-parasitic nematode in the Department of Plant Pathology and Microbiology. He can be reached at firstname.lastname@example.org or 515-294-3021