Development of an oligonucleotide probe for Aureobasidium pullulans based on the small-subunit rRNA gene.

Aureobasidium pullulans, a cosmopolitan yeast-like fungus, colonizes leaf surfaces and has potential as a biocontrol agent of pathogens. To assess the feasibility of rRNA as a target for A. pullulans-specific oligonucleotide probes, we compared the nucleotide sequences of the small-subunit rRNA (18S) genes of 12 geographically diverse A. pullulans strains. Extreme sequence conservation was observed. The consensus A. pullulans sequence was compared with other fungal sequences to identify potential probes. A 21-mer probe which hybridized to the 12 A. pullulans strains but not to 98 other fungi, including 82 isolates from the phylloplane, was identified. A 17-mer highly specific for Cladosporium herbarum was also identified. These probes have potential in monitoring and quantifying fungi in leaf surface and other microbial communities.