First Report of Fruit Rot Caused by Phytophthora palmivora on Fig in Brazil

In Brazil, figs (Ficus carica L.) are the third most exported fruit. In 2011, widespread fig fruit rot symptoms were first noticed for two consecutive years in commercial orchards in the cities of Colombo and Quatro Barras, Paraná state, southern Brazil, at an incidence of approximately 5%. Symptoms and signs first developed on fruit closer to the ground and consisted of brown, circular lesions with white surface mycelia. Isolations were made from symptomatic fruit fragments onto 2% water-agar medium containing ampicillin (80 ppm), chloramphenicol (40 ppm), and benomyl (40 ppm), and consistently yielded a Phytophthora spp. Two isolates from Colombo and Quatro Barras were purified through hyphal typing, and deposited in the mycological collection of the plant disease epidemiology laboratory of the Federal University of Paraná (accession nos. FigPhy01 and FigPhy02). Cultural features consisted of non-dense aerial mycelium with a slightly cottony and petaloid colony pattern on carrot agar (CA). Sporangia formed abundantly on CA and were ellipsoid, papillate, deciduous, and sympodial, with a L × W range of 39 to 60 × 21 to 36 μm (avg. 48 × 21 μm) and ratio from 1.4 to 1.8. Globose chlamydospores were terminal, measuring 33 to 45 µm (avg 33 µm). The isolates were identified as A1 mating type by pairing each isolate with known A1 (AN61) and A2 (AN65) tester strains of Phytophthora frigida. Antheridia were amphigynous and oospores globose, aplerotic. Optimum growth temperatures were between 24 and 28°C, with limited growth taking place at 8°C, and no growth occurring at 36°C on CA. Morphological characteristics resembled P. palmivora (E. J. Butler) E. J. Butler (†). Identification of the two isolates was confirmed through sequence analyses of the rDNA internal transcribed spacer (ITS1-5.8S-ITS2) region. The sequences of the isolates (790 and 799 bp) were deposited in GenBank (KY357520 and KY357521) and had 100% similarity with P. palmivora, accession no. KT148925. Pathogenicity of the two isolates was determined using 20 detached fig fruits (2 weeks before harvest) with and without wounding (wounds made with a 1 mm diam. needle, 4 mm deep). All fruits were inoculated with 4 mm diameter discs obtained from P. palmivora colonies growing on CA for 4 days. Controls were inoculated with CA disks, and all fruits were kept in a moist chamber at 25°C and 90% humidity. The experiment was performed twice. Inoculated wounded and nonwounded fruits had an infection period (IP) of 3 and 4 days respectively, and symptoms as first observed in the field. Isolates did not differ in virulence, and no symptoms were observed on control fruit. P. palmivora was reisolated from infected fruits. This is the first confirmed report of fig fruit rot caused by P. palmivora in Brazil, but it has been reported in the United States (†), China (†), Japan, Taiwan, and Australia (†). The results of this study will contribute to the development of fruit rot management strategies in Brazil. © 2017, American Phytopathological Society. All rights reserved.