Phyllactinia corni

Phyllactinia corni was first described by H.D. Shin and M.J. Park in 1988, but it was not effectively published. The species was formally described in the Taxonomic Manual of the Erysiphales in 2012.^[1] The type specimen was collected in South Korea on Cornus officinalis, and only a specimen from Japan has been sequenced, which proved distant from a single sequence of Phyllactinia on Cornus in Germany, suggesting that P. corni is actually multiple species.^[2] The specific epithet derives from the host genus.

The mycelium is hypophyllous (found on leaf undersides) and sometimes covers the entire surface. The hyphal appressoria are nipple-shaped, rod-shaped or lobed and occur both solitarily and in opposite pairs. Conidophores arise centrally from their mother cell. They have very long foot cells that are straight with a basal septum generally not elevated. The conidiophores produce single conidia. Conidia are clavate with a rounded apex, and can be faintly pigmented. The chasmothecia (fruiting bodies) have 5–16 straight, pointed appendages around the equator, which have a bulbous basal swelling. The peridium of the chasmothecia has cells of irregular shape. Phyllactinia corni has two spores per ascus which are roughly ellipsoid and at first faintly olive-coloured, becoming colourless. The asci are typically clavate or saccate and are stalked.

Hyphal cells measure 10–110 × 3–8 μm. Conidiophores are up to 50–325 μm long and 5–8 μm wide, with foot cells that measure 70–200 μm long. Conidia are 50–95 × 14–30 μm. The chasmothecia are 150–265 μm in diameter with peridium cells 5–25(–30) μm in diameter. Appendages are 0.8–2× the diameter of the chasmothecia and 6–12.5 μm wide near the base. Asci generally number 10–25 and are 50–90 × 25–40 μm with ascospores measuring 20–55 × 15–23 μm.