Botrytis cinerea is a necrotrophic fungus that causes gray mold disease in strawberries, leading to significant pre- and post-harvest losses. Considering there are no strawberry cultivars that show complete resistance to gray mold, this research is aimed at screening a selected set of germplasm consisting of both strawberry Cultivars and MSU Lines as promising candidates for breeding parents to develop resistance to B. cinerea, thereby reducing the use of chemical pesticides on strawberries. Our other goal is to see where advanced MSU Lines stand compared to Cultivars for tolerance to B. cinerea. The experiments were conducted in 2021 and 2022 with the fruits harvested from plants maintained in the Pathology Farm at Michigan State University (MSU). In total, 26 different genotypes were examined for their disease severity, Titratable Acidity (TA), and Soluble Solids Content (SSC). The Area Under the Disease Progress Curve (AUDPC) was calculated to quantify the level of tolerance, and the correlation between AUDPC to SSC and TA was analyzed to determine if there is any correlation. Allstar and Camarosa showed moderate tolerance, agreeing with previous studies on determining tolerance in literature. Three MSU Lines, MSU69, MSU78, and 14_30_4 were more tolerant than most of the genotypes evaluated. Although Cultivars performed better in general, many MSU Lines appeared to be significantly better than some Cultivars, such as Earliglow and Jewel. We also observed a positive correlation between SSC and AUDPC for Cultivars; however, TA did not show a correlation with disease severity. Overall, MSU Lines could be stated as moderately susceptible to gray mold; however, MSU69, 78, and 14_30_4 were found to be promising lines to be used as parents along with cultivars tolerant to B. cinerea to increase the level of tolerance in the MSU germplasm.
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