Retrotransposon Microsatellite Amplified Polymorphism Strain Fingerprinting Markers Applicable to Various Mushroom Species

The retrotransposon marY1 is a gypsy family retroelement, which is detected ubiquitously within the fungal taxonomic groups in which mushrooms are included. To utilize marY1 as a molecular marker for the DNA fingerprinting of mushrooms, oligonucleotides marY1-LTR-L and marY1-LTR-R were designed on the basis of highly conserved regions from the multiple sequence alignment of 30 marY1 sequences retrieved from a nucleotide sequence database. In accordance with Retrotransposon Microsatellite Amplified Polymorphism (REMAP) fingerprinting methodology, the two oligonucleotides were utilized together with the short sequence repeat primers UBC807 and UBC818 for polymerase chain reaction using templates from different mushroom genomic DNAs. Among the tested oligonucleotides, the marY1-LTR-L and UBC807 primer set yielded the greatest amount of abundance and variation in terms of DNA band numbers and patterns. This method was successfully applied to 10 mushroom species, and the primer set successfully discriminated between different commercial mushroom cultivars of the same strains of 14 Pleurotus ostreatus and 16 P. eryngii. REMAP reproducibility was superior to other popular DNA fingerprinting methodologies including the random amplified polymorphic DNA method.

Isolation of Bacteria Associated with the King Oyster Mushroom, Pleurotus eryngii

Eight distinct bacteria were isolated form diseased mycelia of the edible mushroom, Pleurotus eryngii. 16S rDNA sequence analysis showed that the isolates belonged to a variety of bacterial genera including Bacillus (LBS5), Enterobacter (LBS1), Sphingomonas (LBS8 and LBS10), Staphylococcus (LBS3, LBS4 and LBS9) and Moraxella (LBS6). Among them, 4 bacterial isolates including LBS1, LBS4, LBS5, and LBS9 evidenced growth inhibitory activity on the mushroom mycelia. The inhibitory activity on the growth of the mushroom fruiting bodies was evaluated by the treatment of the bacterial culture broth or the heat-treated cell-free supernatant of the broth. The treatment of the culture broths or the cell-free supernatants of LBS4 or LBS9 completely inhibited the formation of the fruiting body, thereby suggesting that the inhibitory agent is a heat-stable compound. In the case of LBS5, only the bacterial cell-containing culture broth was capable of inhibiting the formation of the fruiting body, whereas the cell-free supernatant did not, which suggests that an inhibitory agent generated by LBS5 is a protein or a heat-labile chemical compound, potentially a fungal cell wall-degrading enzyme. The culture broth of LBS1 was not inhibitory. However, its cell-free supernatant was capable of inhibiting the formation of fruiting bodies. This indicates that LBS1 may produce an inhibitory heat-stable chemical compound which is readily degraded by its own secreted enzyme.