A Novel Quantitative Trait Locus Reduces Fusarium graminearum Infection in Glycine max Seedlings

Over the past 5 years, seedling diseases have caused an average annual loss of $21.8 million worth of United States' soybean (Glycine max) production, with Fusarium graminearum (teleomorph Gibberella zeae) emerging as a significant threat within the seedling disease complex. Its cross-pathogenicity on wheat and maize, along with increasing reports of fungicide resistance, highlights the need for improved genetic resistance in soybean. In a previous germplasm screening and genome-wide association study, we identified a significantly resistant accession, PI 438500, from a panel of 208 diverse soybean accessions. This accession carried fewer marker-trait associations and lower predicted resistance than other significantly resistant accessions yet displayed a highly resistant phenotype with low standard deviations. In this study, we developed an F_2:3 mapping population from a biparental cross between PI 438500 and PI 548631 (highly susceptible to F. graminearum) and identified a quantitative trait locus (QTL) that explains 20.29% of the variation in postemergent visual severity. This QTL region contains multiple candidate genes with predicted roles in plant defense mechanisms and helps elucidate PI 438500's significant resistance to F. graminearum. Molecular markers linked and within this QTL region can help facilitate marker-assisted selection for F. graminearum resistance in soybean breeding.