The soybean cyst nematode (SCN) continues to be a major yield-reducing pathogen of soybeans in Iowa, and it occurs in up to 75 percent of fields in the state. Growing SCN-resistant soybeans is an important part of managing SCN.
Results from Iowa State University’s nine SCN-resistant variety trial experiments in 2013 illustrate how resistant varieties can produce high yields and suppress the buildup of the nematode in infested fields

Tylka, Gregory

English

The soybean cyst nematode (SCN) continues to be a major yield-reducing pathogen of soybeans in Iowa, and it occurs in up to 75 percent of fields in the state. Growing SCN-resistant soybeans is an important part of managing SCN.
Results from Iowa State University’s nine SCN-resistant variety trial experiments in 2013 illustrate how resistant varieties can produce high yields and suppress the buildup of the nematode in infested fields.</p

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3/12/2014 trial results show dual benefits of SCN resistancehttp://www.extension.iastate.edu/CropNews/2014/00117tylka.htm 1/4PRINT STORYEMAIL STORYADD TO DELICIOUS ATOM FEEDFOLLOW ON TWITTER Subscribe to CropNewsArchives2014201320122011201020092008 Previous YearsISU Crop ResourcesExtension FieldAgronomistsCrop & Soils InfoPesticide ApplicatorTrainingAgronomy ExtensionEntomology ExtensionPlant PathologyExtensionAg and BiosystemsEngineering ExtensionAgribusinessEducation ProgramIowa Grain QualityInitiativeCollege of Agricultureand Life SciencesISU ExtensionTrial Results Show Dual Benefits of SCNResistanceThe soybean cyst nematode (SCN) continues to be a major yield-reducingpathogen of soybeans in Iowa, and it occurs in up to 75 percent of fields inthe state. Growing SCN-resistant soybeans is an important part of managingSCN.Results from Iowa State University’s nine SCN-resistant variety trialexperiments in 2013 illustrate how resistant varieties can produce highyields and suppress the buildup of the nematode in infested fields. The ISU SCN-resistant Soybean Variety Trial Program, in its 23rd year ofoperation, is funded by the soybean checkoff through a grant from the IowaSoybean Association. The program is the largest and most thorough atevaluating SCN-resistant varieties for agronomic performance andnematode control in the United States.The results of all of the experiments from the ISU SCN-resistant SoybeanVariety Trial Program conducted in 2013 are currently available online atwww.isuscntrials.info.  The complete, printed annual report of the 2013results was distributed in the January 18, 2014, issue of the Iowa FarmerToday. The agronomic performance and/or nematode control provided by individualSCN-resistant soybean varieties last growing season varied significantly ineach variety trial. Some SCN-resistant soybean varieties performeddifferently among experimental locations. The variable performance ofvarieties among experimental locations was due, at least in part, todifferences in population densities and in the aggressiveness of the SCNpopulations (HG types) present in the different fields. Also, differences inenvironmental conditions among the experimental sites contributed todifferences in performance of varieties. Environmental conditions greatlyaffect soybean growth and development and also the nematode-soybeanhost-parasite relationship. Resistant varieties yielded 5 to 50 percent greaterThe SCN-resistant varieties yielded greater, on average, than the widelygrown susceptible varieties at all nine variety trial locations in 2013 (figure 1).The experiment conducted near Glenwood, in the southwestern corner ofIowa, had the greatest overall yields, where SCN-resistant varieties yieldednearly 70 bushels per acre, an average of 3.7 bushels per acre (or 5.6percent) more than the widely grown SCN-susceptible varieties in theexperiment. This field had the lowest initial SCN egg population density atplanting of all of the variety trial experiments conducted in 2013.ICM Home ISU Extension Calendar Publications Extension News County Offices Contact Us3/12/2014 trial results show dual benefits of SCN resistancehttp://www.extension.iastate.edu/CropNews/2014/00117tylka.htm 2/4Figure 1. Mean yields of SCN-resistant soybean varieties and widely grownsusceptib le varieties at nine locations in Iowa in 2013. Data for individualvarieties and locations are availab le at www.isuscntrials.info. The greatest difference in average yields between SCN-resistant and widelygrown susceptible varieties in any variety trial location in 2013 was 18.4bushels per acre (or 56 percent), which occurred at the experimentconducted in a very sandy field near Fruitland, Iowa (figure 1).  Overall, soybean yields were the lowest in the variety trial conducted nearNewell, Iowa, in the northwest part of the state. Parts of the experiment wereflooded early in the season at that location.  Nonetheless, yields of SCN-resistant varieties averaged a little more than 37 bushels per acre, whichwas 40 percent greater than yields of the average yield of 26.7 bushels peracre for the widely grown susceptible varieties at that experiment (figure 1). Resistant varieties allowed much less SCNreproductionInitial SCN egg population densities at planting for the nine variety triallocations in 2013 ranged from 431 to 10,952 eggs per 100 cubic centimeters(cc) of soil, which is a little less than a half cup of soil. This was an unusuallywide range of initial SCN population densities among the variety triallocations. The final or end-of-season SCN egg population densities underthe SCN-resistant varieties were one-fifteenth to one-half of the densities thatdeveloped under the widely grown susceptible varieties (figure 2). Theamount of soybean yield loss caused by SCN is directly related to the SCNegg population density, so the nematode control provided by SCN-resistantvarieties will pay dividends in the form of higher yields the next timesoybeans are grown.3/12/2014 trial results show dual benefits of SCN resistancehttp://www.extension.iastate.edu/CropNews/2014/00117tylka.htm 3/4Figure 2. Mean final (end of season) SCN population densities (numbers) ofSCN-resistant soybean varieties and widely grown susceptib le varieties attrial locations in Iowa in 2013. Data for individual varieties and locations areavailab le at www.isuscntrials.info. The greatest level of nematode control provided by SCN-resistant varietieswas at the variety trial near Urbana in 2013 (figure 2). The average SCNpopulation density in the field before the experiment was planted was 431eggs per 100 cc of soil. At harvest, SCN population densities in thisexperiment increased to 1,120 eggs per 100 cc of soil under the SCN-resistant varieties. In contrast, the end-of-season SCN population densityunder the widely grown susceptible varieties in that experiment was 16,350eggs per 100 cc of soil.The greatest amount of SCN reproduction on SCN-resistant varieties, as awhole, occurred in the experiment near Leighton in 2013. The field had aninitial SCN egg population density of 1,694 eggs per 100 cc of soil; finalpopulation densities were 11,745 eggs per 100 cc of soil on average underthe SCN-resistant varieties and 28,267 eggs per 100 cc of soil under thewidely grown susceptible varieties. Resistant varieties are an effective management tool,but not a cureThe results of these experiments illustrate the benefits of growing SCN-resistant soybeans in fields infested with the nematode. But it is important toremember that yields of SCN-resistant soybeans are reduced by SCN,although to a lesser extent than yields of susceptible soybean varieties. Themost profitable soybean production in fields infested with the nematode willcome through integrated management of SCN using nonhost crops, likecorn, in rotation with soybean varieties with varying types of nematoderesistance and in conjunction with nematode-protectant seed treatments asthey become available. More information about managing SCNFor more information about the biology and management of SCN, visitwww.soybeancyst.info and www.planthealth.info/scn_basics.htm.  Iowa StateUniversity’s management recommendations for SCN are available online ina downloadable format, Soybean Cyst Nematode (SCN) ManagementRecommendations, IPM 63. An annually updated list of SCN-resistant3/12/2014 trial results show dual benefits of SCN resistancehttp://www.extension.iastate.edu/CropNews/2014/00117tylka.htm 4/4Copyright ©2014 Iowa State University Extension | Iowa State UniversityContact us | For Staff | Nondiscrimination and Information Disclosures | CMS AdminLast Updated 1/17/2014soybean varieties for 2014 is available in PDF format online at the Iowa StateUniversity Extension and Outreach Online Store. Greg Tylka is a professor with extension and research responsib ilities inmanagement of plant-parasitic nematode in the Department of PlantPathology and Microbiology. He can be reached at gltylka@iastate.edu or515-294-3021. This article was published originally  on 1/17/2014 The inf ormation contained within the article may  ormay  not be up to date depending on when y ou are accessing the inf ormation.Links to this material are strongly  encouraged. This article may  be republished without f urtherpermission if  it is published as written and includes credit to the author, Integrated CropManagement News and Iowa State Univ ersity  Extension. Prior permission f rom the author isrequired if  this article is republished in any  other manner.

Trial Results Show Dual Benefits of SCN Resistance

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Trial Results Show Dual Benefits of SCN Resistance

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