First Report of Phytophthora cinnamomi Causing Root and Crown Rot of Ficus carica in Turkey

Turkey is the largest fig (Ficus carica L.) producing country; production consists of more than 50,000 ha and 300 kt of fruit annually. In April 2017, about 20% of 2-year-old fig trees (cv. Bursa Siyahı) exhibited wilting, foliar chlorosis, and rapid tree decline in an experimental orchard of 1,500 trees at the Serince Station of the GAP Agricultural Research Institute, Şanlıurfa Province, southeastern Turkey (36°53ʹ09ʺ N; 38°55ʹ29ʺ E). The initial symptoms evident in affected plants were lack of vigor and foliar chlorosis, which developed into wilting and whole tree decline within 7 to 10 days. By this stage, dark-brown to black necrosis had developed under the bark of the crown, extending from the tap root and other large roots, and feeder roots had decayed. Crown and root samples of 10 symptomatic plants were surface sterilized in 70% ethanol and cultured on Phytophthora-selective PARPH-GACMA medium (Türkölmez et al. 2015). After incubation in the dark at 26°C for 7 to 10 days, hyphal tips of Phytophthora-like colonies growing from the crown and root tissues were transferred to GACMA. These isolates developed coralloid hyphae, with spherical lateral and terminal swellings 34 ± 11 μm in diameter, single or in clusters, and globose, terminal, and thin-walled chlamydospores 32 ± 13 μm in diameter. Sporangia, which were produced in nonsterilized soil extract (10 g/liter), were nonpapillate and ovoid, obpyriform, or ellipsoidal with an inconspicuous apical thickening, 60.1 ± 9.6 × 39.5 ± 3.5 µm and a length-to-width ratio of 1.5. These morphological characteristics are consistent with those of Phytophthora cinnamomi (Erwin and Ribeiro 2005). The rDNA internal transcribed spacer (ITS) and β-tubulin gene of two isolates (PH101 and PH102) were amplified with ITS6/ITS4 and Bt2a/Bt2b primer pairs, respectively, and the amplicons sequenced. The 650- and 662-bp ITS nucleotide sequences (GenBank accessions MH680960 and MH680961) had 99.69 and 100% identity with the sequences of P. cinnamomi isolates PD_01134 and PD_02690, respectively, in the Phytophthora Database (http://www.phytophthoradb.org/blast.php). The sequences MH680962 (434 bp) and MH680963 (1,140 bp) for β-tubulin had 100 and 99.73% identity with P. cinnamomi isolates PD_00138 and PD_00138, respectively, thus confirming the morphological identification. Pathogenicity tests were performed on 1-year-old potted F. carica ‘Bursa Siyahı’ seedlings. A 5-mm-diameter colonized GACMA disk was used for inoculating a wound (5-mm diameter) made in the bark of one of the taproots of each of the five seedlings. Five control plants received sterile GACMA disks. Inoculation points were sealed with sterile moist cotton and Parafilm and were covered with sterile soil. Treated plants were maintained in a growth chamber with a 16-h/8-h (light/dark) photoperiod at 26°C and 55% relative humidity and were watered daily. The experiment was repeated. Within 6 weeks, inoculated plants in both experiments developed extensive root necrosis, root loss, and discoloration and death of leaves similar to those observed in naturally affected trees. Control plants remained healthy. P. cinnamomi was only reisolated from inoculated plants, thus fulfilling Koch’s postulates. In Florida, a similar fig disease caused by P. cinnamomi has been reported (Alfieri et al. 1984). In Turkey, P. cinnamomi has previously been reported on walnut (Kurbetli 2013) and protea (Tok and Avci 2015). This is the first report of P. cinnamomi infection of figs in Turkey. This polyphagous pathogen represents a potential threat to commercial fig plantings as well as to other crops in this region.