A list of hundreds of SCN-resistant soybean varieties available for Iowa soybean farmers is compiled every fall as Iowa State University Extension and Outreach publication PM 1649, “Soybean cyst nematode-resistant soybean varieties for Iowa.” In addition to company, brand, and variety name, the list includes information about each variety’s relative maturity, herbicide resistance traits, iron chlorosis tolerance, and genetic source of SCN resistance. The effort is supported by soybean checkoff funds from the Iowa Soybean Association.
There are 818 SCN-resistant soybean varieties included in the new list, which is fewer than in the past eight years (see graph below). But there are varieties from 27 different brands included in this year’s publication, more than in recent years.
More choices of varieties with Peking SCN resistance for 2023 than in the past
Soybean varieties containing SCN resistance from the breeding line named Peking are highly valued. Currently in Iowa, Peking SCN resistance is more effective at limiting nematode reproduction and the buildup of SCN numbers in the soil than resistance from the PI 88788 breeding line, which is used in 95% of the varieties available to Iowa farmers. Yields of varieties with Peking SCN resistance frequently are greater than yields of varieties with PI 88788 SCN resistance because high levels of SCN reproduction on varieties with PI 88788 resistance cause significant yield suppression. ICM Newsletter articles here and here describe the situation in greater detail.
There are 47 varieties with SCN resistance from Peking in the updated publication, 13 more than in the 2021 list and the highest number of such varieties ever in the publication. Most (27) of the varieties with Peking SCN resistance are in maturity group 2. There are 16 varieties in maturity groups 0-1 with Peking resistance, and only 4 varieties are adapted for maturity group 3.
More varieties with Peking SCN resistance are needed
Reproduction of SCN populations present in Iowa fields on the PI 88788 source of resistance and resistant varieties developed with that breeding line has been increasing steadily since the early 2000s. The trend is not expected to subside. The low number of soybean varieties with Peking SCN resistance in maturity group 3 is particularly unfortunate because levels of reproduction of SCN populations on PI 88788 are among the highest in southern Iowa, as explained in a recent ICM News article here.
Links to this article are strongly encouraged, and this article may be republished without further permission if published as written and if credit is given to the author, Integrated Crop Management News, and Iowa State University Extension and Outreach. If this article is to be used in any other manner, permission from the author is required. This article was originally published on November 22, 2022. The information contained within may not be the most current and accurate depending on when it is accessed.
Greg Tylka Morrill Professor
Dr. Greg Tylka is a Morrill Professor in the Department of Plant Pathology and Microbiology at Iowa State University with extension and research responsibilities for management of plant-parasitic nematodes. The focus of Dr. Tylka's research program at Iowa State University is primarily the soybea...