024_JPP594(Kavak)_701 24-11-2009 10:14 Pagina 701 Journal of Plant Pathology (2009), 91 (3), 701-703 Edizioni ETS Pisa, 2009 701 SHORT COMMUNICATION OLEANDER KNOT CAUSED BY PSEUDOMONAS SAVASTANOI pv. NERII IN TURKEY H. Kavak1 and N. Üstün2 1 Plant Protection Department, Agricultural Faculty, University of Harran, 63040 Sanlıurfa, Turkey 2 Plant Protection Research Institute, 35040 Bornova, Izmir, Turkey SUMMARY 2006). The most striking symptom of the disease is vari- ously sized tumors (knots) that develop on trunks, twigs A knot disease was detected on some oleander plants and leaves (Riker et al., 1946). The bacterium can also in two park since 2007 and in one home gardens in deform inflorescences and seed pods, and cause the 2008 in the Sanlıurfa province (south-east Turkey). Al- death of pistils (Smith, 1928; Janse, 2006). More or less though galls were excised in the first year, they devel- similar diseases and pathogens occur in several mem- oped again with a bigger size on the lower parts of the bers of the related family Oleaceae, i.e olive (Olea main stems. Knots on newly infected plants were com- europaea L.), common ash (Fraxinus excelsior L.), privet mon on the upper parts, particularly on twigs, flowers (Ligustrum japonicum Thunb.), Forsythia intermedia and pistils or at the pistil base. Almost all infected (Besenyei and Hevesi, 2003), Jasminum spp. (Iacobellis, plants belonged to cultivars with pink or red flowers. 2001) and in Retama sphaerocarpa (family Fabaceae) Biochemical and pathogenicity tests identified the plant (Alvarez et al., 1998). pathogenic bacterium Pseudomonas savastanoi pv. nerii Since bacterial strains from oleander, olive, ash and as the causal agent of the disease. Although the pres- other oleaceous plants differ from each other in patho- ence of knots on oleander has long been known, to our logical, biochemical and genetic characteristics, they knowledge, Pseudomonas savastanoi pv. nerii had never were recently reclassified by Young (1996). For in- been previously reported on Nerium oleander in Turkey. stance, strains isolated from oleander, ash and olive were denoted P. savastanoi pv. nerii, P. savastanoi pv. Key words: identification, biochemical and patho- fraxini, and P. savastanoi pv. savastanoi, respectively. genicity tests. Other strains from oleaceous and fabaceous hosts were also given different names to suit this classification. When compared by cross-inoculation, oleander strains Nerium oleander (family Apocynaceae) is a cosmo- are virulent to both oleander and olive, whereas olive politan ornamental plant grown especially in temperate strains induce knots on olive only and ash strains infect and subtropical regions. It is native of the Mediter- only this host (Janse, 1982; Surico et al., 1985; Capo- ranean areas of southern Europe and southwest Asia. nero et al., 1995; Iacobellis et al., 1998). More than 40 distinct cultivars are known many of Galls, 0.5 to 5.5 cm in size (Figure 1A) were detected which are commercially available (Pagen, 1988). Olean- on some oleander plants during surveys conducted in der is commonly grown in Mediterranean, Aegean and the Sanlıurfa district (south-east Turkey) in 2007 and Southern regions of Turkey in parks, along city roads, 2008. In 2007, symptomatic plants were pruned by gar- and home gardens. It is more rare in the interior or up- deners in the attempt to control the disease. However, land regions of the country. In the Sanlıurfa district, knot formation was not inhibited, so that more and larg- many different, but unknown oleander cultivars are er galls developed in 2008 also on the main stems of the found. Among oleander diseases, knot caused by plants that had undergone surgical treatment. Knots on Pseudomonas savastanoi pv. nerii is an important and newly infected plants were common on the upper parts, difficult to control bacterial disorder. particularly on twigs, flowers and pistils or at the pistil This disease and its causal agent were first described base. Almost all infected plants were cultivars with pink in California (Smith, 1928) and later studied in more or red flowers. Knots had also been long observed on detail in the USA (Wilson and Magie, 1964) and Europe oleander plants in the provinces of Izmir (Aegean re- (Caponero et al., 1995; Kudela et al., 2005; Bella et al., gion) and Antalya (Mediterranean region). Fresh small knots from oleander leaves were surface sterilised in 70% ethanol for 2-3 min flamed and me- Corresponding author: H. Kavak Fax: +90. 4143440073 chanically crushed in a small amount of sterile distilled E-mail: [email protected] water and the suspension as such or variously diluted 024_JPP594(Kavak)_701 24-11-2009 10:14 Pagina 702 702 Oleander knot in Turkey Journal of Plant Pathology (2009), 91 (3), 701-703 A Fig. 1. A. Knots on trunks of a naturally infected oleander plant at Sanliurfa. B. Knot on an oleander plant 5 months after artificial inoculation. was plated onto King’s medium B (King et al., 1954). REFERENCES Plates were incubated at 26oC for 48 h. Almost pure cultures of cream-coloured, weakly fluorescent bacteria Alvarez F., Garcia de los Rios J.E., Jimenez P., Rojas A., Riche P., Troya M.T., 1998. Phenotypic variability in different were obtained that were subsequently purified on the strains of Pseudomonas syringae subsp. savastanoi isolated same medium. From other typical galls, collected from from different hosts. European Journal of Plant Pathology other parts of oleander plants, similar colonies were re- 104: 603-609. peatedly isolated on King’s B. Basım H., Ersoy A., 2001. Identification of Pseudomonas Four representative strains (two from Sanlıurfa, one savastanoi pv. savastanoi, olive knot pathogen, by poly- each from Izmir and Antalya) were identified using bio- merase chain reaction. Phytopathology 91: S6. chemical and pathogenicity tests. The strains were fluo- Bella P., Catara V., Guarino C., Cirvilleri G., 2006. Evaluation rescent on King’s B medium, were Gram, levan produc- of oleander accessions for resistance to Pseudomonas savas- tion, oxidase, arginine dihydrolase and potato rot nega- tanoi pv. nerii. Journal of Plant Pathology 88: 273-278. tive, induced a hypersensitive reaction on tobacco leaves Besenyei E., Hevesi M., 2003. Characterization of Pseudo- within 24 h after infiltration, grew at 37oC, reduced ni- monas savastanoi pv. forsythiae pv. nov. - a novel pathovar trate to nitrite, did not hydrolyse gelatine and utilized of knot disease bacterium. Novenyvedelem 39: 123-128. cellobiose and trehalose, but not mannitol and sorbitol. Caponero A., Contesini A.M. Iacobellis N.S., 1995. Popula- In pathogenicity tests two-year-old oleander plants tion diversity of Pseudomonas syringae subsp. savastanoi on with pink flower were inoculated by injection of a sus- olive and oleander. Plant Pathology 44: 848-855. pension (107 cells x ml-1) of each bacterial strain into Iacobellis N.S., Caponero A., Evidente A., 1998. Characteri- stems of the shoots. Control plants were injected with zation of Pseudomonas syringae ssp. savastanoi strains iso- lated from ash. Plant Pathology 47: 73-83. sterile water only. Inoculated plants (six per strain) were Iacobellis N.S., 2001. Olive knot. In: Maloy O.C., Murray incubated at 23-27ºC and in 100% relative humidity for T.D., (eds): Encylopedia of Plant Pathology, Vol. 1., 24 h. Tumors began to appear 35 days after inoculation. pp. 714-715. John Wiley & Sons, New York NY. USA. A bacterium was successfully reisolated from these galls Janse J.D., 1982. Pseudomonas syringae pv. savastanoi (ex 60 days after inoculation (Fig. 1B) and identified as Smith) subsp. nov. rev, the bacterium causing excrescences Pseudomonas savastanoi pv. nerii using the tests de- on Oleaceae and Nerium oleander L. International Journal scribed above. No symptoms developed on controls. of Systematic Bacteriology 32: 166-169. P. savastanoi pv. savastanoi has been previously re- Janse J.D., 2006. Phytobacteriology: Principles and Practice, ported from olive in Turkey (Basım and Ersoy, 2000; CABI Publishing, Wallingford, UK. Mirik et al., 2006) and, recently, a fungal pathogen was Kavak H., 2007. 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