Evaluation of Early-Maturity Soybean Lines for Resistance to Sclerotinia sclerotiorum

Sclerotinia sclerotiorum, the causal agent of Sclerotinia stem rot (SSR), is a fungal pathogen of soybean that can lead to yield losses of more than 11 million bushels in the northern United States. Although resistant cultivars can reduce SSR impacts, limited research has focused on early-maturity soybean lines adapted to the Northern Great Plains because of the lack of appropriate check lines. The primary objective was to screen early-maturity soybean lines and identify those showing consistent responses to different S. sclerotiorum isolates. In this study, we screened 193 diverse soybean lines from the U.S. Department of Agriculture germplasm collection from varying maturity groups (MGs), ranging from 000 to I. Under greenhouse conditions, these lines were inoculated with a highly aggressive isolate of S. sclerotiorum, and the lesion length development was recorded at three independent time points postinoculation. Relative area under the disease progress curve values were generated to evaluate resistance ratings. High resistance was observed in 39% of MG 000 lines, 13.8% of MG 00 lines, and 3.8% of MG 0 lines. Representative resistant, moderately resistant, and susceptible lines were subsequently evaluated against four S. sclerotiorum isolates of differing aggressiveness (WI-20, WI-43, WI-15, and WI-3). Significant line × isolate interactions were observed (P < 0.0001), but PI 194639 and PI 548649 displayed consistent resistance or susceptibility across isolates, respectively. These findings demonstrate the importance of screening with multiple S. sclerotiorum isolates and the identification of potential early-maturity soybean check lines for future SSR resistance evaluations.