Identification and Pathogenicity of Sclerotinia minor Causing Sclerotinia Rot in Stringy Stonecrop

Unusual symptoms of Sclerotinia rot were observed in stringy stonecrop (Sedum sarmentosum) plants cultivated in vinyl greenhouses in Icheon, Korea, during a disease survey conducted in March 2024. The symptoms were characterized as soft rot of stems and leaves at or above the soil line in the early stage. In the late stage, most of the diseased plants collapsed and rotted with white to grayish brown mycelia. Occasionally, black, spherical or irregular, small sclerotia formed on the stems and leaves of the diseased plants. The disease occurred in 1‒3% of the plants in three out of 20 surveyed vinyl greenhouses. Three isolates of Sclerotinia sp. were obtained from diseased stems and identified as Sclerotinia minor based on their morphological characteristics and phylogenetic analysis. The pathogenicity of the S. minor isolates to stringy stonecrop plants was tested through artificial inoculation. The tested isolates induced Sclerotinia rot symptoms in the inoculated plants, which were similar to those observed in the disease survey. This study reveals that S. minor is one of the causal fungi of Sclerotinia rot in stringy stonecrop.