| Characteristics |
Lesions commonly present on leaves, causing discoloration of the affected tissues, initially pale green to yellow, later becoming brown to dark brown, polyangular, vein-limited, frequently covering larger areas by coalescing. Down present on the lower leaf surface, whitish, consisting of dense, felt-like conidiophore outgrowth forming patches. Conidiophores (270–)310–464–618(–810) μm long, with the trunk 8–13 μm wide below the first branch, clearly monopodially branched, and with the first branch arising at 2/10–4/10 of the total conidiophore length. Branching occurs in 3–5(–6) orders. Callose plugs are always present in both the trunk and branches. Ultimate branchlets are straight to substraight and 5–24 μm long. Vesicles (n = 50) are irregular rather than spherical, 8–12 μm in diameter, and bear 3–5 extensions, each 4–7 μm long; the tips of the extensions are obtuse to somewhat swollen and 1.5–2 μm wide. Conidia (n = 30) are ellipsoidal, subhyaline, (19.1–)21.6–25.6–29.5(–32.8) × (15.0–)17.2–20.3–23.4(–25.0) μm, with a length/width ratio of (1.03–)1.16–1.27–1.38(–1.43); a short, conical pedicel is present. |
| Notes |
Bremia saussureae is a host-specialized downy mildew associated with Hemistepta lyrata in East Asia. Although formerly included in the broad concept of B. lactucae, morphological and multilocus phylogenetic analyses clearly supported its recognition as an independent species (Choi et al., 2011). Molecularly characterized specimens from Korea and Yantai, China, formed the same lineage, confirming its occurrence in both countries. Broader multigene analyses further supported its distinct phylogenetic position and the importance of host shifts followed by specialization in the diversification of Bremia (Choi and Thines, 2015). |
