Soybean screening identifies resistant lines, reveals virulence variation, and genomic diversity among Minnesota Sclerotinia sclerotiorum isolates

Sclerotinia stem rot (SSR), caused by Sclerotinia sclerotiorum (Lib.) de Bary, is a serious disease of soybean that continues to cause major yield losses in the Upper Midwest. Despite advances in management, host genetic resistance remains the most sustainable strategy for reducing disease impact. This study was designed with three primary objectives. First, we evaluated a diverse panel of 51 soybean varieties, including commercial cultivars and breeding lines from the University of Minnesota’s soybean program, to characterize their resistance responses to SSR under controlled conditions. This large-scale screening revealed a resistance spectrum from highly susceptible to highly resistant lines. Based on these results, our second objective was to identify a smaller subset of soybean varieties representing high, moderate, and low levels of resistance and to assess their interactions with eight S. sclerotiorum isolates collected across Minnesota. This allowed us to evaluate whether host–pathogen interaction patterns are consistent and reproducible for our screening panel. The third objective was to assess virulence and genetic diversity among Minnesota S. sclerotiorum isolates. This work advances SSR management in three main ways. It identifies soybean varieties with strong and consistent resistance to accelerate breeding for improved SSR resistance. It characterizes virulence and genetic variation among Minnesota isolates of S. sclerotiorum, providing a glimpse into region-specific variation and genetic resources for future virulence studies. It also establishes a reliable variety–isolate screening panel that offers a practical tool for researchers and breeders to improve the accuracy and efficiency of soybean resistance evaluation against SSR.