Soybean cyst nematode (SCN) is a persistent threat to growers throughout Minnesota. Fields infested with SCN are more susceptible to other disease, pest, and environmental stresses. Moreover, some parts of Minnesota have seen a breakdown in varietal resistance, with the appearance of new SCN races capable of overcoming the widely grown 88788-source of resistance. Developing new germplasm with alternative forms of resistance to combat resistance breakdown for long-term success is an important function of the public sector breeding efforts. With this in mind, our overall objective is to advance the development of SCN-resistant soybean varieties as well as provide accurate and unbiased sources of information on the resistance of commercial soybean varieties. Our specific aims are to: 1) Enhance the efficiency and efficacy of breeding for SCN resistance through the deployment of DNA markers linked to major genes conferring SCN resistance; 2) Advance new sources of SCN resistance and expand the use of these new sources for crossing in the breeding program; 3) Conduct SCN bioassays on commercial varieties entering the 2023 UMN Variety Trials, as well as all non-88788 commercial SCN varieties available to Minnesota growers.

Goals 1. Continue to efficiently produce new SCN-resistant germplasm and varieties and thus expand availability of SCN resistance across all maturity groups grown in Minnesota.
Objective 1. Deploy DNA markers linked to genes conferring SCN resistance to enhance the efficiency and efficacy of breeding for SCN resistance.

Goals 2. Create elite soybean germplasm with non-88788 sources of SCN resistance so that future soybean growers have more tools in their toolbox to compete with this evolving major pest of soybean.
Objective 2. Advance new sources (non-88788) of SCN resistance and expand the use of these new sources as parents for crossing in the breeding program
Goals 3. Provide an unbiased source of information to growers on the level of SCN resistance in 88788-type commercially available varieties as well as those that have non-88788 sources of resistance.
Objective 3. Conduct SCN bioassays on commercial varieties entering the 2023 UMN Variety Trials using race 3, and conduct bioassays on commercially available non-88788 SCN varieties using races 3 and 14.

1) Public and licensed SCN-resistant varieties, particularly ones carrying the non-88788 source of resistance such as Peking and 567516C; 2) An unbiased source of information on the actual SCN resistance of currently available 88788-type resistant varieties to race 3 (HG Type 0); and 3) An unbiased source of information on the resistance of advertised non-88788 resistant varieties to SCN race 1 (HG Type 2.5.7).

Updated September 12, 2023:
Objective 1: Over 4700 individual F4 plants were sampled and samples were sent off to a private vendor for DNA analysis. Data on DNA markers will be returned in the coming weeks, and these data will be used to select and harvest individual plants. This activity greatly enriches our breeding pipeline for SCN resistance.

Objective 2: This past summer we made 17 new crosses involving a non-88788 source of SCN resistance. These F1 seeds are developing on the plant and will be harvested soon and sent to Chile. We also grew 23 F2 populations and 16 F4 populations in St. Paul and Rosemount. The plants were healthy all season and will be advanced through either single-seed descent (F2 pops) or plant pulls (F4 pops) in the coming weeks. Additionally, over 600 plant rows, 90 PYT entries, 66 AYT entries, and 1 regional trial entry were grown in yield trials this summer. Each entry was grown in randomized trials at 2, 3, or >4 locations for PYT, AYT, and regional trials, respectively. Data will be summarized for selections after harvest.

Objective 3: We solicited seeds of non-88788 SCN resistance commercial varieties for a verification bioassay. We received seeds of 12 commercially available varieties, which is many more than in the past. Seeds were sent to Waseca for a bioassay using HG Type 2 (i.e., a SCN population capable of overcoming 88788-type resistance). We have not received results yet but expect to in the coming months. We also sent 63 commercial varieties in for HG Type 0 testing. We did receive results and found that seven of the 63 commercial varieties were susceptible to SCN. These results will be published in our annual MN State Variety Trials report.

Updated November 8, 2023:
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The proposed research addresses three areas targeted by the Production Action Team’s mission statement: (1) Plant breeding and genetics; (2) Molecular breeding and functional genomics; (3) Soybean cyst nematode (SCN). The work we propose aims to increase soybean yield and profit potential by providing growers with a broader range of variety options with stable or enhanced yield even in fields infested by SCN. To increase the utility of our work, we are introducing novel sources of resistance into Minnesota soybeans, combining SCN resistance with other marketable traits, and making our germplasm available to the broader community to catalyze additional variety development for the future benefit of Minnesota growers. We will also provide an unbiased source of information on the SCN resistance of commercially available varieties. This is particularly important for the non-88788 varieties, which have not been verified in this way before.