First Report of Phellinus ferruginosus Causing Laminar Root Rot on Juniperus communis in Spain
Authors: González V. , Tuset J. J. , Hinarejos R. 
Published: May 2007

During 2004, the natural juniper forests of the Mediterranean mountain ranges of Castellón and Valencia provinces (Comunidad Valenciana, eastern Spain) were severely affected by wood decay. A 2-year drought was registered in the area, and analyzed soil samples had high rates of conductivity (as much as 1,400 μS/cm) in the vicinity of diseased stands. Disease patches occurred within a 2-ha area (with a density of 5 to 30 stands per hectare), and tree damage varied in these symptomatic stands ranging from having chlorotic foliage (10 to 20% of the total surface) to complete defoliation and death of entire stands. After removing dead trees, a white laminated rot was observed located at their bases, specifically on the collar of the roots and the branches in contact with the substrate. In addition to these symptoms, annual, poroid, resupinate, ferruginous-colored basidiocarps were found on 90% of the infected or dead trees in each stand surveyed. These basidiocarps were characterized by having a dimitic hyphal system without clamp-connections, hymenial and hyphal thick-walled setae. Basidiospores were thin-walled, smooth, oblong, and ranged in size from 5 to 7 × 3 to 3.5 μm (4 × 4 μm, extreme measures). On the basis of these features, fungal fruitbodies were preliminary characterized as belonging to Phellinus ferruginosus (Schrad.: Fr.) Pat. (= Fuscoporia ferruginosa (Schrad.) Murrill.). Besides morphological identifications, isolations from infected wood were obtained. Infected branches of Juniperus communis were transversely sectioned and fragmented in small chips (0.5 × 0.5 cm ) that were surface sterilized and placed on potato dextrose agar (PDA) supplemented with 0.5 mg/ml of streptomycin sulfate. Emerging colonies were then transferred to PDA and malt agar plates and incubated at 26°C for 15 to 20 days with a 12-h photoperiod. Cultures also identified as P. ferruginosus had submerged hyphae with swellings, hyphal setae, and ochraceous, tawny-to-honey yellow colonies (3). To confirm pathogenicity, healthy 2-year-old J. communis seedlings (40 replicates) were artificially inoculated with P. ferruginosus (isolate PHE-05-S30). Inoculum was grown on millet grains colonized by the fungus under sterile conditions and subsequently dehydrated. Two grams of the millet grain were applied at the base of the stems and 2 grams were mixed with potting substrate. Pots were covered with plastic bags for 5 days and incubated at room temperature for an additional 25 days. After this period, P. ferruginosus was reisolated (90% recovery) from rotten pieces of wood placed on petri dishes containing PDA, thus fulfilling Koch's postulates. In Europe, this fungus was previously reported to occur on living J. communis in southern Italy (1) and could be distinguished from other closely related Phellinus spp. (2). To our knowledge, this is the first report of white laminated rot on Juniperus spp. caused by P. ferruginosus in Spain.

References: (1) A. Bernicchia. Mycotaxon 75:241, 2000. (2) L. Ryvarden and R. L. Gilbertson. European Polypores. Part 2: Meripilus-Tyromyces. Synopsis Fungorum. Vol. 7. Fungiflora, Oslo, Norway, 1994. (3) J. A. Stalpers. Stud. Mycol. 16:1, 1978.