Stacking Resistance Alleles from Wild and Domestic Soybean Sources Improves Soybean Cyst Nematode Resistance

The soybean cyst nematode (SCN; Heterodera glycines Ichinohe) is the most economically important soybean [Glycine max (L.) Merr.] pathogen in the United States. Field SCN populations are adapting to the narrowly based SCN resistance currently deployed in soybean cultivars. The objective of our research was to measure the effects of combinations of SCN resistance genes or quantitative trait loci (QTL) from the wild soybean (Glycine soja Siebold & Zucc.) PI 468916 and the domesticated soybean accessions PI 88788 and PI 437654. Two populations were developed to test the combinations of QTL and genes. Both populations segregated for the G. soja resistance QTL cqSCN-006 and cqSCN-007. Population 1 also segregated for resistance from PI 88788 and Population 2 segregated for resistance from PI 437654. The populations were tested for resistance to three SCN isolates in a greenhouse and with single nucleotide polymorphism (SNP) and simple sequence repeat (SSR) markers. In both populations, the two G. soja resistance alleles significantly increased SCN resistance compared with the alternative alleles. The SCN resistance alleles rhg1 and Rhg4 from PI 437654 and rhg1-b from PI 88788 also significantly increased resistance compared with the alternative alleles. The two G. soja QTL alleles significantly enhanced the resistance derived from PI 88788. These results show that SCN resistance can be increased through stacking genes and QTL from multiple resistance sources.