First Report of Powdery Mildew Caused by Podosphaera xanthii on Hydrocleys nymphoides in Korea

In October 2013, Hydrocleys nymphoides (Willd.) Buchenau, known as waterpoppy, was found infected with a powdery mildew and lost its ornamental value with 100% infection. The waterpoppy was grown in a pot and placed in the window side of a building in Seoul, Korea. Powdery mildew colonies were circular to irregular or thinly effuse on adaxial side of the leaves. A voucher specimen was deposited in the Korea University Herbarium (KUS). Appressoria on the hyphae were nipple-shaped or nearly absent. Conidiophores were straight, 115 to 180 × 10 to 12.5 μm and produced 2 to 5 immature conidia in chains with a crenate outline. Foot-cells of conidiophores were cylindric and 40 to 60 μm long. Conidia were ellipsoid-ovoid to barrel-shaped, measured 30 to 40 × 19 to 23 μm with a length/width ratio of 1.3 to 1.9, and had distinct fibrosin bodies. Primary conidia were apically conical or rounded, mostly truncate at base, and generally smaller than secondary conidia. Dark brown chasmothecia were found partly embedded ...