First Report of Phytophthora palmivora Causing Crown and Root Rot on Pear ( Pyrus communis ) Trees in Turkey

Disease symptoms such as small leaf development in early spring and the following growing period, wilting, and decline were observed in a pear orchard with 400 nine-year-old trees in Bursa Province, Turkey. In November 2012, ten plants showing these symptoms also had brown rot that extended from fine and capillary roots to the crown and basal stem. A species of Phytophthora was isolated consistently from the roots and crowns of symptomatic plants. Samples were washed free of soil in tap water. Advancing margins of the lesions were cut into 1-cm super(2) pieces; soaked in 70% ethanol for 1 min; dried on filter paper; placed on plates of carrot agar (CA) containing pimaricin, ampicillin, rifampicin, and pentachloronitrobenzene; and maintained at 28[degrees]C for 7 days. Hyphal tips of clean cultures were then transferred and maintained on CA. Isolates of this species had slightly stellate striated growth on CA. The species developed prominently papillate, caducous sporangia of different shapes ranging from ellipsoid to spherical (predominantly ellipsoid with a broad base) on short pedicels (4 [mu]m). Sporangia were 35 to 55 x 25 to 35 [mu]m (average 45 x 30 [mu]m), L:B ratio from 1.3 to 1.8. Chlamydospores approximately 34 [mu]m in diameter were also produced; all fit the description of Phytophthora palmivora(E. J. Butler) E. J. Butler (Gallegly and Hong 2008). Pathogenicity tests were carried out on 1-year-old potted pear plant cv. Deveci by placing ten 5-mm-diameter disks from the advancing margin of P. palmivora colony grown on V8 agar around the primary roots of the plants after removing 10 to 15 cm of soil around the base. Root parts were covered with soil and soil was kept wet by watering plants daily as required. Three months later, all inoculated plants showed extensive root necrosis and dieback symptoms similar to those observed in the orchard, and P. palmivora was reisolated from roots of symptomatic plants. Control plants remained healthy. The pathogen identification was confirmed by BLAST analysis of ITS region of rDNA amplified with ITS6/ITS4 primer pair (Martin et al. 2012). Nucleotide sequences showed 99 to 100% identity of P. palmivora isolates deposited in GenBank (e.g., 100% identity with isolate Accession No. EU194438 from Spain and 99% identity with isolate Accession No. AB367359 from Japan) and Phytophthora database. The nucleotide sequences were submitted to GenBank as Accession No. KP985659. To our knowledge, this is the first report o