Soybean Cyst Nematode (SCN): Part 3 - Tools against a silent robber

Soybean cyst nematode (SCN) is the #1 hidden yield robber in soybeans. It also has a long evolutionary history with soybean, first documented in 1915 and believed to have been present in China for thousands of years prior to commercial production. Over this time, the soybean developed tools to resist the damage from the pest. For the last 70 years, researchers have been looking for genetic sources of resistance and have been able to catalog seven. Of the seven, only two have been successfully deployed for commercial use. These two sources are known as PI88788 and Peking.

1. Mechanisms of Resistance

Plant pathologists have two general categories for genetic resistance. Partial resistance from many genes and R-gene mediated resistance from a single dominant R-gene. R-genes function as an alarm system, detecting the presence of the pathogen and signaling for a response. PI88788 and Peking sources contain different R-genes; PI88788 has Rhg1b, and Peking has both Rhg1a and Rhg4. Resistance to SCN depends not just on the presence of these genes but also on the copy number. This means varieties with the same source of resistance may not provide the same amount of protection.  

📸: BASF internal photograph/Featuring a microscopic view of Soybean cyst nematode (SCN).

2. Durability of Resistance

One of the main differences between PI88788 and Peking is how quickly the nematode dies after feeding on resistant roots. The Peking source initiates a rapid response, killing both male and female nematodes. The PI88788 response is slower and selectively kills females due to their longer feeding time in the root. Selectively killing only females allows susceptible males to reproduce, effectively providing a refuge. Peking source of resistance doesn’t provide this refuge, allowing the nematode to overcome this resistance quicker. 

3. Adding layers of protection.

Reducing yield loss to SCN depends on laying protection. No single tool is effective at stopping the damaging effects of root feeding from the nematode. The first and simplest layer is an effective seed treatment that can kill nematodes. ILEVO^® Seed Treatment is the only effective product for SDS and nematodes, and it is active against all plant parasitic nematodes. Second, utilize both sources of PI88788 and Peking, rotating across fields.

Allowing at least four years between the use of Peking in any field will delay the development of resistance. Finally, a new trait for protection against SCN has been developed by BASF, with an anticipated launch by 2028. A novel BT toxin is being utilized to provide season long protection that will increase yields in SCN infested fields and extend the longevity of our native resistance sources.  

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