What are scientists projecting for the future of soybean cyst nematode?
Fig. 19. Field plots of the soybean cyst nematode and soybean breeding research projects at the University of Minnesota Southern Research and Outreach Center at Waseca. (Photo courtesy of David Hansen)
Soybean production has continued to increase in the past few decades, and it will remain a major crop in Minnesota. Successfully managing SCN will continue to be a key factor for profitable soybean production. SCN management, however, will face serious challenges in the future due to limited sources of resistance, extensive soybean production, and the shift of HG Types.
SCN will continue to spread in Minnesota due to unpreventable natural means and human activities. At the present time, more than 40% of soybean fields in Minnesota are not infested by SCN or have an undetectable level of SCN. All of these fields have a high risk for SCN infestation. Early detection of SCN in fields is important to minimize its damage to soybean, especially in the Red River Valley, where SCN was recently detected.
Within the next five years, PI 88788 and Peking will still be the major sources of SCN resistance in commercial soybean varieties. With the extensive use of the SCN-resistant varieties from PI 88788, the frequency of HG Type 2-, and the percentage of the fields with an SCN FI > 30, to which PI 88788 resistant varieties are ineffective, will continue to increase. Within the next few years, the choice for these fields will be to use Peking varieties. Although PI 437654 (CystX) varieties are highly resistant to SCN populations in Minnesota, yield potential of current PI 437654 varieties is still lower than from other sources of SCN resistance.
Peking and PI 88788 carry two distinct types of resistance, and they are good in rotation, at least within a foreseeable period of time. However, it is unclear what the trend of HG Types will be following the rotation of these two sources of resistance. Similarly, it is unclear whether planting Peking varieties in fields having HG Type 2- will change the SCN populations to other Types so that the PI 88788 can be used again or the resulting SCN populations can overcome both PI 88788 and Peking.
Researchers at the University of Minnesota, and other institutions and companies continue to breed for highyielding soybean varieties with current and new sources of SCN resistance. The development of new, powerful DNA markers and advances in molecular biology will speed up breeding new SCN-resistant varieties. Yield potential of PI 437654 varieties will continue to be improved, and varieties with new sources of resistance will probably be available in 5-10 years.
Long-term effective management of SCN will rely on an integrated program that includes resistant soybean varieties, crop rotation, and possibly alternative strategies such as soil fertility management and biological control. Although it is unclear whether or not there will be any cost-effective commercial biological control agents on the market in the near future, better understanding of the roles of natural parasites in regulating SCN populations in fields may help to develop strategies to lower SCN populations through practical cultural methods.