Direct analysis from wood of the blue stain fungi Aureobasidium pullulans and Hormonema dematioides by denaturing gradient gel electrophoresis
M J Ray, D J Dickinson
Aureobasidium pullulans and Hormonema dematioides are the two organisms used in the EN 152 laboratory method for determining the effectiveness of preservatives against blue stain in service. The literature concerning the disfigurement of surface coatings and exposed timber in-service states that A. pullulans is the dominant blue stain fungus, due to its frequent isolation from stained material. Inaccuracies when differentiating morphologically between isolates of these two related species have previously been highlighted bringing the conclusion concerning the dominance of A. pullulans to question. PCR-DGGE has been used to determine the environmental profile of the two blue stain fungi; A. pullulans and H. dematioides and to establish which of these organisms is most prevalent on a range of stained timber samples taken from trials and in service. The DGGE analysis indicated that a member of the Dothioraceae family, most likely H. dematioides was more commonly present on stained timber samples under five years old. No blue stain fungi were detectable by PCR-DGGE in older samples over 25 years old. With the correct primer choice PCR-DGGE is able to differentiate between different species and the level of abundance at which those species are represented in a sample. It is clear from this study that A. pullulans is not as dominant on stained timber as would have been expected. On this basis it is suggested that H. dematioides should be the preferred species for research and development work in this field.
Keywords: Aureobasidium, Hormonema, PCR-DGGE, blue stain in service