First Report of Kumquat Shoot Blight Caused by Phytophthora citrophthora in Turkey

Abstract

HomePlant DiseaseVol. 100, No. 5First Report of Kumquat Shoot Blight Caused by Phytophthora citrophthora in Turkey PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of Kumquat Shoot Blight Caused by Phytophthora citrophthora in Turkeyİ. Kurbetli, G. Sülü, M. Aydoğdu, M. Özdemir, S. M. Sülü, and İ. Polatİ. KurbetliSearch for more papers by this author, G. SülüSearch for more papers by this author, M. AydoğduSearch for more papers by this author, M. ÖzdemirSearch for more papers by this author, S. M. SülüSearch for more papers by this author, and İ. PolatSearch for more papers by this authorAffiliationsAuthors and Affiliations İ. Kurbetli G. Sülü M. Aydoğdu M. Özdemir S. M. Sülü İ. Polat , Bati Akdeniz Agricultural Research Institute 07010 Antalya, Turkey. Published Online:4 Mar 2016https://doi.org/10.1094/PDIS-10-15-1154-PDNAboutSections ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat Kumquats (Fortunella spp.) are citrus plants valued as ornamentals and for their edible fruit. Their production is increasing in Turkey. During March-April 2014 and 2015, potted kumquat saplings cv. Nagami (oval kumquat) showing shoot blight were observed in two commercial nurseries in Antalya Province, Turkey. The plants were grown in greenhouses and drip irrigated. At least half of the plants were affected. Symptoms were leaf discoloration, defoliation, cankers girdling the shoots, and gummosis on twig blight. Severely affected plants died within 1 to 2 months. Small sections of 3 to 5-mm-diameter from shoots were cut from the margin of lesions; 10 to 12 sections were plated onto selective PARPH medium, in which corn meal agar (CMA) was the base (Jeffers and Martin 1986), and incubated at 22°C in darkness for 3 days. Emerging colonies were transferred to carrot agar (CA) (200 ml boiled carrot juice, 800 ml distilled water, 20 g agar) containing 20 mg/1 β-sitosterol. A Phytophthora sp. was consistently isolated from necrotic shoot tissues. Isolates did not produce sexual structures in single culture. They formed colonies with a rosette pattern on PDA and slightly rosette patterns on CA and CMA. They produced papillate and noncaducous sporangia, usually ovoid and obpyriform, sometimes ellipsoid and distorted shapes, rarely with two papillae. Sporangia were 41.6 to 69.8 μm long (mean 53.7 μm) and 26.1 to 43.4 μm wide (mean 32.7 μm). Chlamydospores, produced singly, had 17.4 to 31.1 μm (mean 24.7 μm) diameters. The isolates did not grow at 35°C on CA and PDA. The isolates were identified by morphology as Phytophthora citrophthora (R.E. Sm. & E.H. Sm.) Leonian (Erwin and Ribeiro 1996). This was confirmed by ITS sequences of rDNA. After DNA extraction of the isolates, ribosomal DNA fragment amplified with ITS1 and ITS4 primers was sequenced. Nucleotide sequences of the isolates (GenBank Accession Nos. KR534890 and KR534891) showed a 99 to 100% homology with other P. citrophthora isolates (e.g., KC412067, HQ697232, EF193229, GU133068, and KJ755103). To test pathogenicity, shoots of five 1-year-old kumquat saplings cv. Nagami grafted on Trojer Stranji rootstocks were inoculated with 3-mm mycelial agar plugs from 5-day-old culture grown on CA. Five saplings inoculated with sterile agar plugs were used as control. Plants were kept in a controlled glasshouse at 25 ± 1°C and watered as needed. Canker lesions developed on shoots within four weeks, while control plants remained symptomless. The pathogen was reisolated from symptomatic shoot tissues, thus fulfilling Koch’s postulates. Phytophthora citrophthora causes root and fruit rot, trunk canker, and gummosis on citrus trees in Mediterranean climates (Graham and Menge 2000; Erwin and Ribeiro 1996). It was responsible for severe outbreaks of Phytophthora blight in ornamental citrus nurseries including mainly kumquats of coastal area of Sicily in Italy (Magnano di San Lio et al. 1986). To our knowledge, this is the first report of P. citrophthora causing this type of disease on kumquats in Turkey.