| Scientific Name | Bremia sawadae Ji H. Park, Thines, H.B. Lee, H.D. Shin & Y.J. Choi, Nova Hedwigia 107 (3-4): 312 (2018) |
|---|---|
| Synonyms | - |
| Disease | Downy mildew |
| Taxonomic Rank | |||
|---|---|---|---|
| Order | Peronosporales | Family | Peronosporaceae |
| Host Plant | |||
|---|---|---|---|
| Common Name | Teeth-margin crepidiastrum (이고들빼기) | Scientific Name | Crepidiastrum denticulatum |
| Distribution | China, Korea |
|---|---|
| Characteristics | Lesions commonly causing discoloration of the tissues, yellowish to dark brownish, often vein-limited, poly-angular, frequently covering larger areas by coalescing; infected tissues become necrotic. Down present on the under surface of host leaf, whitish, consisting of scattered conidiophores, only one to three in a fascicle, sparse. Conidiophores emerging through stomata, colourless, straight, (350–)401–461–521(–550) µm; trunk straight, (224–)288–374–460(–514) µm long, (5.4–)6.2–7.1–8.0(–9.4) µm wide below the first branch, basal end not differentiated to slightly bulbous, (6.1–)7.6–9.2–10.8(–12.9) µm wide; callose plugs often present in trunk rarely present in branches; branches dichotomous, 4–6 orders. Ultimate branches in pairs in most cases, rarely single, reflex to curved, 6–22 µm long; vesicles spherical or irregular globose to bowl-shaped, 8–10 µm diam., bearing 4–6 ultimate branchlets with lengths of 5–7 µm. Conidia colourless, ovoid, almost symmetrical at the equatorial plane, (12.3–)13.1–14.2–15.4(–16.8) µm long, (11.1–)12.2–13.0–13.8(–14.5) µm wide, l/w ratio (0.93–)1.03–1.10–1.17(–1.26) greatest width median to submedian, tip round, base broadly round; pedicel mostly present, with a thin-walled papilla from which a germ tube is produced, up to 300 µm long. Resting organs not seen. |
| Notes | Bremia sawadae was described from Korean collections on Crepidiastrum denticulatum based on detailed morphological comparison and six-locus phylogenetic analyses (Park et al., 2018). These collections had previously been identified as B. ovata, but formed a distinct lineage separate from true B. ovata on Youngia japonica. The recognition of B. sawadae demonstrates that morphologically similar downy mildews occurring on closely related East Asian Cichorieae can represent distinct host-specialized species. |
| Economic importance | Crepidiastrum denticulatum is an economically relevant edible leafy plant in Korea, where its young shoots are traditionally consumed. Consequently, B. sawadae has potential agricultural importance in areas where the host is commercially cultivated, although quantitative yield losses have not yet been documented. The pathogen should therefore be monitored in commercial production (Park et al., 2018). |
| References | Park, J. H., et al. 2018. Nova Hedwigia 107:303. |
