Intraspecific genetic diversity of Chaunopycnis alba detected by random amplified polymorphic DNA assay

Abstract

Some isolates of the cosmopolitan fungus Chaunopycnis alba are producers of Cyclosporin A, a potent immunosuppressive compound. In order to determine the taxonomic and geographic relationships of cyclosporin producers, the genetic variation among 90 isolates from 26 geographical locations was analysed by the random amplified polymorphic DNA (RAPD) assay. As an outgroup, closely related taxa (Chaunopycnis ovalispora Tolypocladium cylindrosporum, Sesquicillium microsporum) as well as the distant relative Thelebolus microsporus were included in this study. 297 different DNA fragments of 0·5 to 2·7 kb were obtained using eight 10-mer and one 22-mer primers of arbitrary nucleotide sequences. Computer analysis of these data showed a high genetic diversity within C. alba. The Jaccard coefficients indicated that 87% of all amplified DNA fragments were different between all the C. alba isolates examined. The differences between isolates of C. alba and those from other taxa were in the same range. Similarity values higher than 40 % were obtained only for C. alba isolates derived from samples of the same geographic location and for several strains from various geographic provenances that were all Cyclosporin A producers. The relatively high similarity coefficient between antarctic isolates in comparison with coefficients between strains from other geographic locations could be related to the recent introduction of this fungus into the antarctic habitat.