| Scientific Name | Hyaloperonospora parasitica (Pers.) Constant., Nova Hedwigia 74: 310 (2002) |
|---|---|
| Synonyms | 2 synonyms≡ Botrytis parasitica Pers., Obs. Mycol. 1: 96 (1796).
≡ Peronospora parasitica (Pers.) Fr., Summa veg. Scand. 2: 493 (1849). |
| Disease | Downy mildew |
| Taxonomic Rank | |||
|---|---|---|---|
| Order | Peronosporales | Family | Peronosporaceae |
| Host Plant | |||
|---|---|---|---|
| Common Name | Shepherd's-purse (냉이) | Scientific Name | Capsella bursa-pastoris |
| Distribution | China, Germany, Korea, Spain; widely reported elsewhere on Capsella bursa-pastoris |
|---|---|
| Characteristics | Lesions present on leaves, stems, peduncles, and fruits, causing discoloration of the tissues and deformation of the attacked organs. Down whitish, consisting of scattered conidiophores to dense, felt-like. Haustoria lobate, large, filling the host cell partly to almost completely. Conidiophores colorless, stout, straight to substraight, (300.0–)383.9–461.4–539.0(–570.0) μm long; trunk mostly straight, 80-350 μm long, base not or somewhat swollen, up to 20 μm wide, variable in width, 8-15 μm wide above the base, 8-18 μm wide below the first branch; callose plugs absent or very rarely present; branching upper part monopodially or subdichotomously branched 3-5(-7) orders. Ultimate branchlets in pairs or rarely single, flexuous to sigmoid, (9.5–)11.5–14.3–17.1(–24.1) μm long, (1.4–)1.9–2.6–3.3(–3.8) µm wide at the base and becoming narrower upwards, apex obtuse. Conidia hyaline to subhyaline, subglobose to ovoidal, (19.8–)22.6–24.2–25.7(–26.7) μm long, (17.6–)19.1–20.1–21.1(–24.9) μm wide, l/w ratio (1.01–)1.12–1.20–1.28(–1.33) (n=30), greatest width median, base and tip round; pedicel absent in most conidia but a scar visible at the point of attachment; producing germ tubes at randomly located sites. Resting organs oogonia globose to irregular, 40-55 μm diam., wall smooth or wrinkled, brownish, 3-6 μm thick; oospores plerotic to aplerotic, globose, 24-32 μm diam., wall smooth, yellowish to brownish |
| Notes | Historically, Hyaloperonospora parasitica (= Peronospora parasitica) was broadly applied to downy mildews occurring on numerous genera of Brassicaceae. Molecular phylogenetic studies, however, support a narrower species concept in which H. parasitica sensu stricto is primarily associated with Capsella bursa-pastoris. Molecularly characterized accessions from C. bursa-pastoris are known from Germany, Spain, China, and Korea, supporting a geographically widespread lineage associated with this host (Göker et al. 2009; Lee et al. 2017). In Britain and Ireland, H. parasitica s.s. is also widely recorded on C. bursa-pastoris, where heavy infections may cause extensive white sporulation and deformation of affected plants. Earlier records of P. parasitica from other brassicaceous hosts, including Brassica, Raphanus, and Arabis, should be interpreted cautiously because many such records belong to distinct host-specialized species under the current classification. |
| Economic importance | No quantitative economic losses caused by H. parasitica sensu stricto have been documented. Its principal host, Capsella bursa-pastoris, is a widespread wild and agricultural weed. Nevertheless, severe infections can produce extensive white sporulation, leaf discoloration, and deformation of leaves and stems, as reported from Britain and Ireland. The pathogen is therefore primarily important as a widespread disease of wild and weedy Capsella rather than as a direct crop pathogen. |
| References | Constantinescu, O., and Fatehi, J. 2002. Nova Hedwigia 74:291. Göker, M., et al. 2009. Mycol. Res. 113:308. Lee, J. S., et al. 2017. Mycobiology 45:139. Shin, H. D., and Choi, Y. J. 2006. Peronosporaceae of Korea. NIAST, Suwon. |
