Application of the random amplified polymorphic DNA using the polymerase chain reaction for efficient elimination of duplicate strains in microbial screening. I. Fungi.

For efficient fungal strain selection in microbial screening, we applied the random amplified polymorphic DNA (RAPD) method using the polymerase chain reaction (PCR). In order to evaluate this system, the genus Trichoderma was employed, because its species are difficult to distinguish from each other. We selected an appropriate oligonucleotide decamer, R28 (5'-ATGGATCCGC), determined the optimal cycles of PCR as 30 cycles, simplified the template preparation method, and determined optimal concentrations of the template and Taq DNA polymerase. We then examined 74 closely related strains of Trichoderma. The electrophoretic band patterns of the PCR products were compared. According to the statistical analysis with the phylogenetic analysis using parsimony (PAUP), the results were consistent with the morphological, physiological and ecological data on these strains. Therefore, we conclude that RAPD is a simple, efficient and reliable method for the selection of fungal strains employed in screening.