Soybean cyst nematode (SCN) occurs in most soybean production areas with multiple, complex, and ever-changing races, representing the most damaging pest in soybean. The genetic resistance provided by the rhg1 locus is the most used in soybean production against SCN. Two resistance alleles identified at the rhg1 locus, rhg1 in Peking and rhg1-b in PI88788, have been widely used in breeding for SCN resistance. The rhg1 gene cluster was also reported as a 31-kilobase segment per haploid genome consisting of an amino acid transporter, an α-SNAP protein, and a WI12 (wound-inducible domain) protein, each contributing to resistance with one copy per haploid genome in susceptible varieties, three tandem copies in rhg1 and 10 tandem copies in rhg1-b. It is validated in this study that rhg1-b showed higher levels of resistance to SCN HG Type 0 (race 3) than rhg1 in response to HG Type 0 based on QTL analysis for single allele at rhg1 locus although the rhg1 donor Peking shows high resistance to HG Type 0.  However, the soybean lines (PI 88788) containing 10 copies of rhg1-b showed moderately susceptible to HG Type 2.5.7 (race 1) and HG Type 2.7 (race 5) while the lines (Peking) containing only three copies of rhg1 showed high resistance, indicating existing another mechanism for resistance to HG Type 2.5.7 and HG Type 2.7 beyond copy number variation of multiple genes at rhg1 locus. Single nucleotide polymorphism (SNP) markers are developed from the rhg1 cluster that can identify and differentiate rhg1 and rhg1-b alleles present in various soybean germplasm. Research is under way to combine, through marker assisted selection, rhg1 and rhg1-b into high-yielding cultivars with high levels of resistance to multiple HG types of SCN.