Resistant varieties continue to be a key tool for managing the soybean cyst nematode (SCN). With financial support from the soybean checkoff through the Iowa Soybean Association, Iowa State University annually compiles a list of SCN-resistant soybean varieties that are available for use in Iowa.
The updated list of maturity group 0, I, II and III varieties is now available for free online in the Iowa State University Extension Store.
The 2019 list contains information on 891 varieties, 71 more than were in the 2018 list. The varieties in the 2019 list are offered by 24 companies and Iowa State University.
A majority of the varieties in the updated 2019 list possess SCN resistance from the PI 88788 breeding line. This has been the situation for many years (see graph below). Unfortunately, many SCN populations throughout Iowa and other Midwestern states have developed increased reproduction on PI 88788 resistance.
Consequently, SCN-resistant soybean varieties with resistance from PI 88788 are not as effective at managing SCN as they were 20 to 25 years ago.
In the 2019 list, 850 (95%) of the varieties have resistance from PI 88788. There are 41 varieties with resistance other than from PI 88788, and 38 of those varieties have resistance from the Peking breeding line. Varieties with Peking SCN resistance are available from 14 seed companies (see table below) as well as from Iowa State University.
Planning for 2020
Active management of SCN starts by testing fields to know where the nematode is present and to assess its population densities (numbers), followed by growing nonhost crops and soybean varieties with different sources of SCN resistance and using seed treatments in an integrated approach. The Iowa State University Plant and Insect Diagnostic Clinic processes soil samples for SCN, as do numerous private soil-testing laboratories throughout the state and region.
Looking to the Future
There are efforts underway to develop new and unique options for SCN resistance. Transgenic approaches to SCN resistance are being developed by industry, as recently reported in the media. Also, university soybean breeders have developed soybean lines with unique and stacked combinations of SCN resistance genes from different sources.
These soybean lines are being grown in different sequences in field studies in Illinois, Iowa, and Missouri funded by the North Central Soybean Research Program to determine how best to deploy the new resistance lines to maximize their durability by minimizing buildup of SCN populations on the new lines.
Learn more about SCN
The SCN Coalition is a national, coordinated effort involving universities, private industry partners, and national, regional, and state soybean checkoff organizations working to help soybean farmers and their advisers manage SCN. The SCN Coalition also has Canadian university and private industry partners.
For more information about the project and its wide range of information and resources, go here. Also, research results and other information about the biology and management of SCN can be found online at soybeancyst.info and at soybeanresearchinfo.com.