ENDOPHYTIC FUNGAL DNA, THE SOURCE OF CONTAMINATION IN SPRUCE NEEDLE DNA

DNA isolated and amplified from higher plants may originate from symbi otic microbes occupying plant tissues. A recent report on the phylogen y of Picea contained sequence data that upon later analysis proved to originate from filamentous ascomycetes. Isolates of endophytic fungi f rom Picea foliage collected from the same location as the original sam ples were examined to identify the source of the contaminating DNA. Th e ITS region of isolates was screened by Southern blotting using an ol igonucleotide probe homologous to a unique portion of the reported 'sp ruce' sequences. This study identifies a DNA sequence originally attri buted to Picea engelmannii (Engelmann spruce) as Hormonema dematioides , a ubiquitous foliar endophyte of conifers. Infections of plants by e ndophytic fungi are common and their presence is not revealed by exter nal symptoms. Plant molecular researchers should be aware of the poten tial for this type of DNA contamination.