Characterization of a Plasmopara sp. detected on Smyrnium olusatrum in Italy.

Each year since 2009, in April-May, downy mildew symptoms and signs on leaves of Smyrnium olusatrum L. plants were observed in Perugia (Central Italy). They were characterized by chlorotic- yellow angular spots and a white mat in correspondence of the diseased areas on the upper and lower leaf surface, respectively. The white mat was constituted by sporangiophores aggregated in 4-14 fascicles, stout with a straight or slightly curved trunk and with a noticeably bulbous base. On each sporangiophore alternate branches were present, showing monopodial branching in one order. Sporangia were ovoidal with base and tip round and with apical dehiscence. Globose to irregular oospores, with smooth, colourless to yellowish, thick wall were present in the infected leaves. Haustoria were pyriform to vesicular. Phylogenetic analysis performed on partial sequences of the large subunit of the nuclear ribosomal DNA revealed that the pathogen fell in a cluster with Plasmopara species attacking hosts belonging to the Apiaceae family. Molecular analyses on downy mildew-affected S. olusatrum herbarium specimens are in progress to establish to which species the pathogen we describe belongs.