Heterobasidion species detected using High Throughput Sequencing (HTS) methods on British Columbia nursery plants

Abstract

A total of 15 out of 26 local and imported plant samples from British Columbia nurseries were obtained, and following DNA extraction, PCR was conducted to amplify the fungal ribosomal ITS region which was sequenced using High Throughput Sequencing methods. Bioinformatics analysis of these sequences revealed the presence of Heterobasidion irregulare and H. occidentale. A total of 529 Heterobasidion Illumina DNA sequence reads were found in the 13/15 successfully PCR amplified plant samples, with H. irregulare comprising 86% of the Heterobasidion DNA reads and was more commonly found (13/15 samples) than H. occidentale (10/15 samples). Previously, H. irregulare has been mentioned only once before as being present in BC. The presence of Heterobasidion DNA in nearly all successfully PCR amplified samples from plants grown locally or recently imported, is interpreted as the result of local spore dispersal, likely originating from nearby infected trees. This raises the question whether asymptomatic nursery plants can participate in the spread of H. irregulare in BC and elsewhere in Canada.