Search for a command to run...
Peronospora silvestris Gäum., Annales Mycologici 16 (1–2): 199. 1918. Fig. 16 Description. Lesions often hardly visible and systemic, infected plant parts often discolouring at later stages, drying or getting necrotic in Veronica officinalis; lesions chlorotic, then turning dark brown to brown upon drying, often vein-delimited in Globularia nudicaulis. Down present on the lower leaf surface, consisting of scattered to dense felt-like conidiophore outgrowth. Conidiophores hyaline, straight to curved, thin-walled, 332–490 µm long, av. 441 µm; trunk 203–309 µm long, av. 256 µm, 6–9.5 µm broad, sometimes slightly swollen to up to 14 µm at the base, ratio of the total length to trunk length 1.5–2, callose plugs absent. Branching subdichotomous in 4–7 orders, with sub-straight to curved branches, gradually attenuate, often at acute angles. Ultimate branchlets sub-straight to curved, paired branchlets differing in length, with the longer ones 9.5–14.5 µm long, the shorter ones 6–8.5 µm long, with a ratio of the longer to the shorter ultimate branchlet of 1.4–1.9, base 2–2.5 µm broad, apex slightly sharp. Conidia ellipsoid to elongate with a dark brown colour, 24–31 µm long, 15–20 µm broad, length-to-breadth ratio 1.4–1.85, basal part of the conidia mostly protruding. Oospores not observed. Type host. Veronica officinalis (Gäumann 1918). Confirmed hosts. Veronica officinalis and Globularia nudicaulis. Reported hosts. Veronica officinalis (Gäumann 1918), V. urticifolia (Gäumann 1923; Riethmüller et al. 2002). Reported distribution. Austria, Denmark, France, Germany, Italy. Spain, Sweden, Switzerland (Gäumann 1923; Riethmüller et al. 2002). Specimens examined. AUSTRIA. Styria: District of Judenburg, Municipality of Pusterwald, forest path near Assmann, on living leaves of Veronica officinalis, 14 Jun 2011, H. Voglmayr and I. Greilhuber (WU-MYC 0032802); District of Judenburg, Municipality of Pusterwald, Hinterwinkel, Waldschlag at Vorderer Pölsenbach, on living leaves of Veronica officinalis, 14 Jun 2011, H. Voglmayr and I. Greilhuber (WU-MYC 0032803). SWITZERLAND. Canton of Bern: Boltigen, Berner Oberland, on living leaves of Globularia nudicaulis, 29 Jul 2016, T. Brodtbeck (GLM-F 135693); Canton of Uri: Spiringen, Klausenpass, on living leaves of Globularia nudicaulis, 24 Aug 2016, T. Brodtbeck (GLM-F 135692). Notes. Gäumann (1918) described P. silvestris on Veronica officinalis, the type host, but also recorded it on Veronica urticifolia (Gäumann 1918, 1923). Subsequently, a specimen (AR 194) collected from Veronica urticifolia was identified as P. silvestris based on its host (Riethmüller et al. 2002). However, phylogenetic analysis based on the LSU sequence (AY 035490) placed specimens from these hosts on a separate branch, with the parasite of V. urticifolia being a previously unrecognised species, P. obscura. Morphologically, P. silvestris is characterised by more globose conidia, with a length-to-breadth ratio of 1.6 ± 0.2, distinguishing it from its sister species, P. palustris.