Abstract
Soybean cyst nematode (SCN) is the most destructive soybean pest worldwide. Host plant resistance is the most environmentally friendly and cost-effective way of mitigating SCN damage to soybeans. However, overuse of the resistant soybean [Glycine max (L.) Merr.] cultivars from limited genetic resources has resulted in SCN race shifts in many soybean-growing areas. Thus, exploration of novel sources of SCN resistance and dissection of the genetic basis are urgently needed. In this study, we screened 235 wild soybean (Glycine soja Sieb. & Zucc.) accessions to identify genotypes resistant to SCN HG Type 2.5.7 (race 5), a less investigated type but is prevalent in the southeastern US. We also dissected the genetic basis of SCN resistance using a genome-wide association study with SNPs genotyped by SoySNP50k iSelect BeadChip. In total, 43 resistant accessions (female index < 30) were identified, with 10 SNPs being significantly associated with SCN HG 2.5.7 resistance in this wild species. Furthermore, four significant SNPs were localized to linked regions of the known quantitative trait locus (QTL) rhg1 on chromosome 18. The other four SNPs on chromosome 18 and two SNPs on chromosome 19 are novel. Genes encoding disease resistance-related proteins with a leucine-rich region, a mitogen-activated protein kinase (MAPK) on chromosome 18, and a MYB transcription factor on chromosome 19 were identified as promising candidate genes. The identified SNPs and candidate genes will benefit future marker-assisted breeding and dissection of the molecular mechanisms underlying the soybean-SCN interaction.
Highlights
Soybean [Glycine max (L.) Merr.] is one of the most important economic crops
Phenotypic evaluation revealed a broad range of Soybean cyst nematode (SCN) HG 2.5.7 resistance in the 235 G. soja accessions, with female index (FI) values from 3.2 to 277.4% (Figure S1)
To investigate whether the resistance levels of G. soja are related to the original ecological distribution (Figure 1A), the FI values of the resistant accessions were plotted against their country of origin
Summary
Soybean [Glycine max (L.) Merr.] is one of the most important economic crops. It has been cultivated for thousands of years and provides protein for humans and animal consumption. SCN is the most devastating pest that causes severe soybean [Glycine max (L.) Merr.] yield loss worldwide. It has been demonstrated that SCN suppresses seed yield more than any other single soybean pathogen (Wrather and Koenning, 2006). Nematicides have shown some short-term efficacy for SCN management, they are costly and not environmentally friendly. The development and use of resistant soybean cultivars is a cost-effective and environmentally-friendly means of managing SCN. Continuous use of a single resistant cultivar in a certain field generally drives the SCN population to evolve to overcome host resistance, diminishing the utility of any given SCN-resistant soybean cultivar
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