Abstracts of Papers Presented at the Meeting of the Mycological Society of Japan

The grapevine leaf rust fungus, Phakopsora ampelopsidis species complex, is now segregated into three distinct species, P. ampelopsidis, P. euvitis and P. vitis, based on host specificity, life cycle and morphology. Similarities in the spore morphology and host relationships of the three Phakopsora species suggest their close phylogenetic relationships. To determine their possible phylogeny, ITS1 and ITS2 regions including 5.8S gene of small subunit rDNA were amplified by a PCR method, sequenced and generated phylogenetic trees using parsimony and neighbor-joining methods. However, the ambiguous sequences were found in the ITS1 region, which made definite alignment impossible. Therefore, neighbor joining and parsimony trees were constructed using the nucleotide sequence data of the 5.8S rRNA gene and ITS2 region. The reconstructed phylogeny showed that the three species formed distinct clades with a hypothetical common ancestor and separated from the two species of soybean rusts, P. pachyrhizi and P. meibomiae. The results also indicated possible existence of a cryptic species, which may also be parasitic on grapevines.

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During the investigation of epiphytic fungi on needles of Japanese red pine (Pinus densiflora) in Korea, eleven unknown Rhizosphaera strains were isolated. When compared with recorded Rhizosphaera species, the morphological and cultural characters of these isolates differed from existing published species and indicated that they belong to a taxon of their own. The new species was named R. densiflorae and its conidial size was larger than that of R. kalkhoffii and smaller than that of R. pseudotsugae. The new species grew between 5 degree celsius and 35 degree celsius with an optimum growth at 25 degree celsius, whereas R. pseudotsugae showed an optimum growth at 18 degree celsius and did not grow at 22 degree celsius and above. The phylogenies of ITS and beta-tubulin sequences differentiated the new species from other Rhizosphaera species. The trees produced from ITS and beta-tubulin data were identical, but the beta-tubulin tree yielded better resolution and was more strongly supported than the ITS tree by bootstrap analysis. Moreover, the trees supported that the classification of Rhizosphaera species based on the conidial size was phylogenetically significant. In the systematic studies of Rhizosphaera, molecular data apparently played an important role in resolving the true phylogeny of morphologically similar or taxonomically related isolates

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In this research, culture-independent molecular approaches were used in combination with geochemical analyses and community-level physiological profiling to assess effects of mineralogical variation on community composition of microorganisms inhabiting a sandstone gradient. A DNA-based community fingerprinting approach (ARISA: automated ribosomal intergenic spacer analysis) combined with construction of fungal and bacterial rRNA gene clone libraries was used to assess community structure and to identify some of the constituent microbial populations. Molecular data was combined with X-ray diffraction and X-ray fluorescence and by applying multivariate statistics, we identified those chemical properties that notably influenced community structure. It was found that the sandstone supported a varied microbial diversity and community ribotype profiles differed between mineralogically-distinct sandstones in close proximity to each other. Canonical correspondence analysis (CCA) illustrated relationships between certain ribotypes and particular chemical elements. We conclude that these molecular and statistical methods provide a powerful tool for resolving rock-inhabiting bacterial and fungal communities, and their relationship to the mineral nature of the rock substrate.

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