Soybean cyst nematode (SCN) is a destructive disease for soybean production. This disease has now spread to at least 24 soybean-producing counties in North Dakota. Variety resistance is the primary nematode management tactic. SCN is known to be genetically diverse populations and can develop new virulent forms over time due to continuous use of the same sources of resistance. In North Dakota, the virulent type reported before 2015 was only HG type 0 which is considered the least virulent type of SCN. In 2015-2017, several new HG types were detected in North Dakota. Therefore, after a few years, it is necessary to determine the HG types, monitor the virulence changing of SCN populations, and assess their occurrence frequency in soybean fields in the state. Host resistance is among the best approach for managing SCN. Every year, new crosses and breeding lines are developed during the breeding and selection process. Hence, evaluating new soybean breeding lines is essential for understanding their resistance responses to SCN and recommending a list of resistant lines to the NDSU breeding program for developing new soybean varieties with improved resistance to SCN to manage the disease in infested fields.

• Determine the virulent types of SCN in 20 fields to monitor the virulence changing by comparing with previous results.
• Evaluate 50 NDSU soybean breeding lines for their resistance levels to two common SCN populations detected in North Dakota.

• Virulent types (HG types) of SCN populations in infested fields will be disclosed and shared with growers.
• Resistance reactions of 50 soybean breeding lines to SCN will be disclosed and shared with the NDSU soybean breeder.

SCN is an important disease in soybean. The resistant breeding lines identified in this proposed research will be provided to the NDSU soybean breeding program for transferring the resistance to locally adapted susceptible varieties to develop and release new varieties with improved genetic resistance to SCN. Knowledge of virulence types of SCN within the state should greatly influence the choice of populations and HG types used in the resistance assay of new soybean varieties and breeding lines. The proposed research findings will be useful to navigate the use of different resistance sources for growers and the new resistance sources that should be introduced to North Dakota for the soybean breeding program.