First Report of Crown and Root Rot of Plum Caused by Phytophthora megasperma in Turkey

Abstract

HomePlant DiseaseVol. 101, No. 1First Report of Crown and Root Rot of Plum Caused by Phytophthora megasperma in Turkey PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of Crown and Root Rot of Plum Caused by Phytophthora megasperma in Turkeyİ. Kurbetli, G. Sülü, M. Aydoğdu, 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, and İ. PolatSearch for more papers by this authorAffiliationsAuthors and Affiliations İ. Kurbetli G. Sülü M. Aydoğdu İ. Polat , Bati Akdeniz Agricultural Research Institute, 07010 Antalya, Turkey. Published Online:3 Nov 2016https://doi.org/10.1094/PDIS-06-16-0921-PDNAboutSections ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat Three- to four-year-old Japanese plum trees (Prunus salicina L.) in a commercial orchard of Antalya Province showed symptoms of decline in July-August 2015. The aerial symptoms were leaf discoloration and twig dieback, and most of the affected trees were leafless. Reddish brown cankers developing from the root to the stem base were observed. Lateral and feeder roots were decayed. Approximately 100 out of 900 plum trees cv. Black Amber and Black Diamond grafted on Myrobalan 29C rootstocks were affected by the disease. Small segments taken from crowns were cut from the margin of lesions and plated onto selective CMA-PARPH medium (Jeffers and Martin 1986), and incubated at 22°C in the dark for 3 to 5 days. Growing colonies were transferred onto carrot agar (CA) (200 ml boiled carrot juice, 800 ml distilled water, 20 g agar) to obtain pure cultures. Isolates were obtained from three of the five symptomatic plum trees that were analyzed. Isolates produced oogonia on CA with a diameter of 31.8 to 46.8 μm (mean 41.4 μm). Plerotic or aplerotic oospores with paragynous antheridia measured 27.6 to 39.6 μm (mean 35.1 μm) in diameter. Nonpapillate and noncaducous sporangia were ovoid, obovoid, obpyriform, ellipsoid or distorted shapes, with rounded and tapered bases. Ovoid and obpyriform sporangia were 45.0 to 90.5 μm long (mean 62.5 μm) and 25.1 to 51.6 μm wide (mean 36.8 μm). Cultures also produced catenulate rounded hyphal swellings. The isolates were identified by morphology as Phytophthora megasperma Drechs. (Erwin and Ribeiro 1996). Morphological identification was confirmed by sequencing of the rDNA region. Genomic DNA was extracted from one isolate, and the internal transcribed spacer (ITS) region was amplified and sequenced using ITS1 and ITS4 primers. Nucleotide sequence of the isolate (KU843555) showed a 99 to 100% similarity with other P. megasperma isolates in GenBank (e.g., HQ643275, EU301166, DQ486668). To test pathogenicity, five plum seedlings cv. Black Amber grafted on Myrobalan 29C rootstocks were transplanted to a 4-liter pot containing autoclaved peat/perlite mixture (3:1, v/v) mixed with wheat grain inoculum at a rate of 4%. Three seedlings grown in sterile mixture without inoculum were used as control. Plants were incubated in a growth chamber for 4 months at 25 ± 1°C. Seedlings were watered twice a week, and in order to keep the seedlings constantly wet, each seedling was placed in a tray filled with 2 to 3 cm of water. At the end of the experiment, canker lesions occurred on taproots and lateral roots, while no cankers developed in the roots of noninoculated plants. The pathogen was reisolated from symptomatic tissues. To our knowledge, this is the first report of P. megasperma causing crown and root rot of plums in Turkey.