Oxalis purpurea sclerotium rot caused by Athelia rolfsii

Abstract

Over a 3-year period (2015-2017), sclerotium rot was observed on purple wood sorrel (Oxalis purpurea) in the exhibition field of Gyeongsangnam-do Agricultural Research and Extension Services, Jinju, South Korea. Infected plants exhibited blight and rot symptoms. White mycelial mats spread over lesions, and numerous sclerotia formed on the petiole near the soil line. Sclerotia were globoid in shape, 1-3 mm in size, and white to brown in color. The optimum temperature for mycelial growth and sclerotium formation on potato dextrose agar (PDA) was 30 degrees C and the hyphal width was 4-8 mu m. Typical clamp connections were observed in the hyphae of fungi grown on PDA. Molecular identification was conducted by sequencing and analysis of the complete internal transcribed spacer (ITS) rDNA sequence of the causal fungus. On the basis of mycological characteristics, molecular identification, and pathogenicity to host plants, this fungus was identified as Athelia rolfsii. This is the first report of sclerotium rot on purple wood sorrel caused by A. rolfsii.