Pseudoperonospora cubensis Causing Downy Mildew on Luffa aegyptiaca in Korea

In November 2021, sponge gourd (<i>Luffa aegyptiaca</i>) plants with typical downy mildew symptom were observed in Korea. Based on morphological characteristics of sporangiophores and sporangia, combined with molecular phylogenetic analysis of the internal transcribed spacer rDNA and <i>cox</i>2 mtDNA regions, the causal pathogen was identified as <i>Pseudoperonospora cubensis</i> (Oomycota). This is the first report of downy mildew caused by <i>P. cubensis</i> on <i>L. aegyptiaca</i> in Korea. Given that <i>P. cubensis</i> exhibits high disease incidence and severity on many Cucurbitaceae crops, it could pose a significant threat to sponge gourd cultivation.