Plant Pathology (2010) 59, 800 Doi: 10.1111/j.1365-3059.2010.02270.x First report of Plasmopara obducens (downy mildew) on Impatiens walleriana in Norway B. Toppe*, M. B. Brurberg, A. Stensvand and M. L. Herrero Norwegian Institute for Agricultural and Environmental Research, Plant Health and Plant Protection Division, Høgskoleveien 7, 1432 Ås, Norway In August 2008, diseased Impatiens walleriana plants were received from a private garden in Oslo, southeastern Norway. Symptoms on the adaxial side of leaves were pale yellowing without distinct lesions. White downy growth appeared on the abaxial side and on flower buds. Infected leaves wilted and abscised from the stem (Toppe et al., 2008). Microscopic examination of the pathogen revealed hyaline, monopodial sporangiophores with branches arranged at right angles. Sporangia were ovoid and hyaline. Oospores were observed in dried diseased tissue of stems, leafstalks and petals of flower buds. On the basis of symptoms and morphological characteristics, the pathogen was identified as Plasmopara obducens. This species is commonly described on wild and cultivated Impatiens and can be easily distinguished from the other known cause of downy mildew in impatiens, Bremiella sphaerosperma (Constantinescu, 1991; Cunnington et al., 2008). Partial nuclear large ribosomal subunit DNA sequences (650 bp) were obtained using PCR and primers NL1 and NL4 as described by Maier et al. (2003), and found to be identical to sequences of several P. obducens isolates deposited in GenBank (AY035522.1, AY587558.1, EF196869.1). Severe disease attacks were later observed in 2008 on cv. Xtreme in public parks in Oslo and Bergen (southwestern Norway). In 2009, the disease was found outdoors at several places in southeastern Norway (also on cv. Xtreme), and at two different greenhouse-sites on cv. Silhouette grown from cuttings and imported earlier the same year. Koch’s postulates were fulfilled on cv. Xtreme Red by inoculating plants with a suspension of sporangia, covering with plastic for the first 24 h after inoculation, and then maintaining in a research greenhouse (20C, 80–95% RH). Symptoms of downy mildew developed after 14 days that matched those originally observed, together with the morphology of the re-isolated pathogen. This is the first observation of downy mildew caused by P. obducens on I. walleriana in Norway. Earlier, the disease was described outdoors on I. noli-tangere, a native plant in Norway (Jørstad, 1964). So far, it is not known whether the observed pathogen of I. walleriana is the same as the pathogen previously observed in native Impatiens species in Norway. References Constantinescu O, 1991. Bremiella sphaerosperma sp. nov. and Plasmopara borreriae comb. nov. Mycologia 83, 473–9. Cunnington JH, Aldaoud R, Loh M, Washington WS, Irvine G, 2008. First report of Plasmopara obducens (downy mildew) on impatiens in Australia. Plant Pathology 57, 371. Jørstad I, 1964. The phycomycetous genera Albugo, Bremia, Plasmopara and Pseudoperonospora in Norway, with an appendix containing unpublished finds of Peronospora. Nytt Magasin for Botanikk 11, 65–6. Maier W, Begerow D, Weiß M, Oberwinkler F, 2003. Phylogeny of the rust fungi: an approach using nuclear large subunit ribosomal DNA sequences. Canadian Journal of Botany 81, 12–23. Toppe B, Herrero ML, Stensvand A, 2008. Aggressiv bladskimmel påvist i lisespringfrø – ‘‘Flittig-Lise’’. Bioforsk TEMA 3, 1–4. *E-mail: brita.toppe@bioforsk.no. Accepted 11 January 2010 at http://www.bspp.org.uk/ndr where figures relating to this paper can be viewed. Plant Pathology (2010) 59, 800 Doi: 10.1111/j.1365-3059.2009.02249.x First report of Peronospora sp. on sweet basil (Ocimum basilicum) in Cuba E. Martı́nez de la Partea, L. Pérez-Vicenteb*, B. Bernalc and D. Garcı́aa a Central Plant Quarantine Laboratory, National Plant Health Center (CNSV., Ayuntamiento #231, Plaza de la Revolución, Havana City; bPlant Protection Research Institute (INISAV). 110 esq. 5ta F, Playa, Havana City; and cHorticulture Research Institute Liliana Dimitrova, Carretera Bejucal-Quivicán, km 33 ½. Quivicán, La Habana, Cuba In Cuba, sweet basil (Ocimum basilicum) is used fresh, dried and processed for flavouring and fragrances, and as insect repellent in greenhouses. In February 2009 a foliar disease was observed in plots of sweet basil cv. Genovesa, located at the Horticulture Research Institute Liliana Dimitrova in Quivican, Havana province, and in greenhouses for vegetable production in Siboney, Havana City, Cuba. Leaves of infected plants were initially slightly chlorotic, especially near the central vein. Within 2–3 days, a characteristic grey downy growth was evident on the lower surface of infected leaves. Microscopic observations revealed conidiophores 2–7 times dichotomously branched, with length 250–500 lm (average 350 lm) and sterigmata bearing a single conidium. Conidia measured 25–35 · 20–28 lm (average 30 · 24 lm) and were elliptical and greyish in mass. No oospores were found. Pathogenicity tests were carried out twice by inoculating leaves of 40-day-old healthy plants of sweet basil and sage (Salvia officinalis) with a conidial suspension (1 · 105 conidia per mL). Non-inoculated plants served as controls. After 6 days, typical symptoms of downy mildew developed only in the inoculated plants of sweet basil, and Peronospora-type conidiophores were observed developing on the leaves. Two species of Peronospora have been associated with sweet basil: Peronospora lamii (Coosemans, 2004; Belbahri et al., 2005) and Peronospora sp. (Garibaldi et al., 2004; Belbahri et al., 2005). The former has conidia in the range 16–26 · 15–23 lm (average 21 · 18 lm) and the dimensions reported for the unnamed Peronospora sp. conidia were 20–35 · 15–25 lm (Belbahri et al., 2005) and 23–36 · 18–29 lm (Garibaldi et al., 2005). Additionally, the unnamed Peronospora species is not pathogenic on Salvia officinalis, on which P. lamii causes downy mildew (Garibaldi et al., 2005). The conidiophores and conidia of the Cuban samples of Peronospora sp. found in sweet basil were similar in shape, color, and size range as the previously unnamed Peronospora sp. reported by Garibaldi et al. (2005) and are not pathogenic to sage. This pathogen had previously been reported in Italy and France (Garibaldi et al., 2005). This is the first report of a Peronospora sp. on sweet basil in Cuba. References Belbahri L, Calmin G, Pawlowski J, Lefort F, 2005. Phylogenetic analysis and Real Time PCR detection of a presumably undescribed Peronospora species on sweet basil and sage. Mycological Research 109, 1276–87. Coosemans J, 2004. First report of Peronospora lamii, downy mildew on basil (Ocimum basilicum) in Belgium. Parasitica 60, 27. Garibaldi A, Minuto G, Bertetti D, Gullino ML, 2004. Seed transmission of Peronospora sp. of basil. Journal of Plant Diseases and Protection 111, 465–9. Garibaldi A, Minuto A, Gullino ML, 2005. First report of downy mildew caused by Peronospora sp. on basil (Ocimum basilicum) in France. Plant Disease 89, 683. *E-mail: lperezvicente@live.com. Accepted 30 November 2009 at http://www.bspp.org.uk/ndr where figures relating to this paper can be viewed. 800 ª 2010 The Authors Journal compilation ª 2010 BSPP