Phylogenic, molecular and decay analysis of Phialophora species causing soft rot of wood

摘要

Soft rot decay of treated wood in ground contact and loss of service-life remains an important economic issue worldwide. This study determined the identity of unclassified Phialophora strains (204-1, 35-1, TS4M3, 25M3) isolated from wood in-service. Phylogenetic analysis clustered strains into a single clade homologous with Phialocephala dimorphospora. Sequencing of internal transcribed spacer (ITS) rDNA showed minor differences at single bases for strains 35-1 and 25M3. Compatibility occurred between TS4M3, 25M3 and 204-1 but not 35-1, Phialophora lagerbergii or Phialophora botulispora. Birch was more rapidly degraded than pine for all strains, with strain 35-1 least aggressive. Light microscopy showed Type I diffuse soft rot cavity formation reminiscent of P. dimorphospora. Growth rates at 15, 20 and 26°C were similar for TS4M3, 25M3 and 204-1 but always less for 35-1. Strains 35-1 and TS4M3 showed highest Cu-tolerance on CuS04 and micronized copper incorporated into malt extract agar plates. Results indicate the Phialophora spp. A strains represent P. dimorphospora as suggested by strong homology and decay morphology, although considerable intra-variation exists.