Preventing unwanted spread of invasive fungal species in willow (Salix spp.) plantations.
In North America, biomass production of fast-growing trees represents an important forestry and agroforestry practice for bioenergy, bioproducts and phytoremediation. In Canada, imported cuttings are used as the propagation material to establish Short Rotation Intensive Culture (SRIC) of willow. Profiling the mycodiversity of willow cuttings is vital for early diagnosis, prevention or control of exotic diseases. It also helps to identify disease tolerant willow genotypes to increase the survival rate of cuttings and the establishment of high-density tree plantations, free of introduction of alien pathogenic species to the Canadian ecosystems. In this study, a total of 82 fungal taxa were isolated and identified from asymptomatic willow cuttings imported in Canada. The most abundant phylum was Ascomycota, although some Basidiomycota (Agaricales and Tremellales) were also detected. The most abundant fungal taxa belonged to Hypocreales, while the most abundant species belonged to Kabatiella in Dothideales. In vitro and in planta bioassays results, combined with polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE) analyses, revealed that potentially pathogenic species belonging to Glomeraceae, Dermateaceae, Diaporthaceae and Venturiaceae may originate from the willow cuttings, which could be transmitted to tree plantations and spread via standard management and coppice practices. A newly discovered Lecythophora-Coneochaeta complex was the most frequently observed. Pathogenic Cadophora spp. were also detected; they are a potential threat to the health of willow during long cold-storage of cuttings. Among cultivars, SV1 (Salix dasyclados) showed low infection rates and demonstrates the possibility of risk stratification according to willow genotypes.