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POSTERS: Mycology I

P-405 - Assessing Sclerotinia stem rot resistance across early maturity soybean PI lines

Monday, August 4, 2025
4:30 PM - 5:15 PM HST
Location: Exhibit Hall 3
Abstract Text: Sclerotinia sclerotiorum, the causal agent of Sclerotinia stem rot (SSR), is a devastating fungal pathogen that led to yield losses of over 11 million bushels of soybeans in the northern United States in 2022. While resistant cultivars can effectively limit SSR, commercial varieties with high levels of resistance are severely limited. Additionally, suitable check lines for screening early-maturity soybean lines are unavailable. In this study, we screened 196 early maturity (000 to 0) soybean accessions from the USDA germplasm collection against four previously established late maturity soybean check lines (Dwight, 51–23, SSR51, and 52-82B). The greenhouse experiment was conducted in an RCBD. The plants were inoculated at the V5 growth stage with mycelial plugs from a highly aggressive isolate of S. sclerotiorum (WI-20) using the cut-petiole method. Lesion length was measured and collected at 5, 7, and 10 days post-inoculation. Standardized area under the disease progress curve (StAUDPC) values were analyzed to evaluate the level of resistance. While all PI lines showed disease symptoms, the level of resistance varied significantly (P < 0.001). Multiple lines were observed to exhibit greater resistance than the resistant check, 52-82B. The most resistant, moderately resistant and susceptible lines from each maturity group will undergo further evaluation using multiple isolates (WI-20, WI-15 and WI-13) with varying aggressiveness. This research aims to determine new parental lines for crossing and to establish check lines for effectively screening early-maturity lines.