P-408 - Evaluation of inoculation methods for screening Sclerotinia sclerotiorum in soybean

White mold, caused by Sclerotinia sclerotiorum (Lib) de Barry, is a common disease affecting soybean production in the Midwest United States. Identifying disease-resistant genetic resources is important for breeding programs and related research. While several inoculation methods exist, an efficient, cost-effective greenhouse method is needed for reliable resistance screening. This study evaluated five inoculation methods —spray mycelium, drop mycelium, cut stem, petiole, and straw inoculation—compared to a control in a randomized complete block design with six replications. Two soybean cultivars, one moderately resistant (NK28P6XF) and one susceptible (Williams 82), were tested. Disease severity was assessed using qualitative ratings for all methods, while lesion measurements were recorded for the cut stem, petiole, and straw methods. Inoculation methods were evaluated based on inoculum preparation time, disease assessment, reliability, and field applicability. Spray and drop mycelium appeared to induce higher disease severity but relied on qualitative ratings, whereas petiole inoculation allowed easy inoculation and formed clear lesions with a higher disease incidence. However, further validation is needed. Findings from this research will be helpful in large-scale genotype screening in greenhouse trials and for inducing disease under field conditions when the natural infection is inconsistent. Further studies incorporating ascospore inoculation will help compare mycelial and spore-based infection, improving alignment between greenhouse and field evaluations.