New soybean accessions evaluated for reaction to heterodera glycines populations

Soybean cyst nematode (SCN; Heterodera glycines Ichinohe) is a serious pest of soybean [Glycine max (L.) Merr.], in the United States and worldwide. Annual yield losses in the United States are estimated to be more than $1 billion. These losses have remained stable with the use of resistant cultivars, but over time nematodes will adapt to deployed resistance alleles. Currently used resistant cultivars do not have broad resistance. Soybean Plant Introduction (PI) 88788 and its derived cultivars continue to be the primary source of SCN resistance. It is important to identify new accessions with resistance to SCN as the first step to finding new alleles to provide long-term resistance. We have bioassayed in the greenhouse 100 newly available accessions from the USDA Soybean Germplasm Collection. We published methods to bioassay in the greenhouse, including culturing of nematodes to develop near-homogeneous populations for stable reactions on soybeans. Sixty-seven accessions with resistance reaction to Race 2 and/or Race 3 were identified, and SCN resistance was confirmed in replicated multiple tests. Among them, seventeen were yellow seeded. Soybean PIs that were yellow seeded and had resistance to both the races included PIs 512322D, 522186, and 567488B. These are the most desirable sources for development of soybean cultivars with resistance. These soybean lines will be evaluated for their genetic diversity to identify unique types to allow broadening of resistance gene introgression.