Peronospora veronicae-cymbalariae Rayss, Palestine Journal of Botany 3: 160. 1945.

Fig. 17

Description.

Conidiophores hyaline, straight to sub-straight, slightly curved, 208–284 µm long, av. 246 µm; trunk 88–145 µm long, av. 117 µm, 8–11.5 µm broad, sometimes slightly swollen to up to 16 µm at the base, ratio of the total length to trunk length 2–2.5, callose plugs absent. Branching subdichotomous in 4–5 orders, with sub-straight to slightly curved branches, gradually attenuate, often at right angles. Ultimate branchlets with straight to sub-straight, paired branchlets differing in length, with the longer ones 11–18 µm long, the shorter ones 7–12 µm long, with a ratio of the longer to the shorter ultimate branchlet of 1.3–1.75, base 2.5–3.5 µm broad, apex slightly sharp. Conidia ellipsoid to ovate with a grey colour, 27.5–36.5 µm long, 20–26 µm broad, length-to-breadth ratio 1.2–1.6, basal part of the conidia mostly protruding. Oospores 30–57 µm in diameter.

Type host.

Veronica cymbalaria (Rayss 1945).

Reported distribution.

Palestine, Greece, Spain (Rayss 1945; this study).

Specimens examined.

GREECE. Corfu: Troumpettas, Ag. Anna, near the junction, fire site, on the living leaves of Veronica cymbalaria, 21 Apr 2012, H. Voglmayr (WU-MYC 0032810); between Ano Garouna and Vouniatades, near Ag. Athanasios, on the living leaves of Veronica cymbalaria, 22 Apr 2012, H. Voglmayr (WU-MYC 0032812); Troumpettas to Ag. Anna, olive grove, on the living leaves of Veronica cymbalaria, 23 Apr 2012, H. Voglmayr (WU-MYC 0032813). PALESTINE. Without exact locality: on the living leaves of Veronica cymbalaria, 5 May 1937, T. Rayss (type ZT 85386). SPAIN. Andalusia: Cadiz Province, SE Alcala de los Gazules, near El Jautor, Auwald, on the living leaves of Veronica cymbalaria, 17 Mar 2011, H. Voglmayr and W. Jaklitsch (WU-MYC 0032796).

Notes.

Peronospora veronicae-cymbalariae was first identified in Western Asia, specifically in Palestine, in 1945 on Veronica cymbalaria (Rayss, 1945). Following its initial description, no additional records of this species were reported for several decades. However, since 2010, specimens of P. veronicae-cymbalariae have been collected in Europe. Notably, it has been newly recorded in Greece and Spain. Phylogenetically, as previously noted, P. veronicae-cymbalariae has a sister species, Peronospora sp. on Veronica triloba. While no samples of Peronospora sp. were available for detailed description in this study, it is worth mentioning that nuclear loci fail to effectively distinguish between these two species. In contrast, mitochondrial loci provide clear differentiation, emphasising the importance of multi-locus approaches in phylogenetic studies (Choi et al. 2015 b). Morphologically, compared to other Peronospora species infecting Veronica, P. veronicae-cymbalariae is characterised by having the shortest conidiophores and trunks, averaging 246 µm and 117 µm long, respectively, the highest conidiophore-to-trunk length ratio, up to 3.3, and the larger conidia, averaging 32 × 23 µm, with conidia that are the broadest among the species examined, up to 32 µm broad.