Detection of genome-specific ribosomal DNA sequences from bread wheat by a modified PCR-based method

Although the nuclear ribosomal ITS region is the marker most frequently used for the molecular analysis of plant origin, little use has been made of this region to determine the origin of common wheat. The present work demonstrates that the nrITS region is suitable for research on the origin or evolution of wheat, not via direct PCR and sequencing, but by means of a novel PCR technique. This PCR analysis involved a combination of high denaturing temperature and high-fidelity Pfu polymerase, followed by product cloning and the sequencing. In this way sequences were revealed that remained undetected using the conventional technique and that bore traces of earlier hybridisations, allowing conclusions to be drawn on the original ITS sequences of the units involved in the hybridisation. It was demonstrated that the direct nrITS sequence of common wheat may be hybrid in nature, and that the results obtained by means of direct sequencing must be treated with caution in wheat and other allopolyploid organisms. With the help of the method described here, it should be possible to avoid such errors

Changes in the diversity of the mycorrhizal fungi of orchids as a function of the water supply of the habitat

Studies were made on the symbiotic associations of orchids in four habitats with diverse water regimes in order to determine whether there was any difference in the diversity of the symbiotic fungi of orchids in the various habitats. The habitats were classed along an environmental gradient based on the water supplies as follows: 'floating': an extremely wet floating mat, 'wet': terrestrial fens, 'variable': wet habitats that dry out periodically, and 'dry': drier steppe areas in the vicinity of wet habitats. Nine photosynthesising orchid species were included in the study, some of which were habitat-specific (Liparis loeselii, Hammarbya paludosa), while others had a broader range of habitats and were found on several of the habitats examined (Orchis laxiflora ssp. pallustris, Dactylorhiza incarnata, Epipactis palustris). A total of 94 fungal strains were isolated from the orchid roots and seedlings and were identified using nrITS sequence analysis. Representatives of four widely occurring groups of orchid mycobionts were identified, but they were present in different ratios in each habitat. Opposing habitat preferences were observed for two groups of the anamorphic fungus genus Epulorhiza, which are frequent orchid symbionts. The first group (Epulorhiza 1), which includes the fungal partner of Liparis loeselii, was dominant in the floating habitats, where no members of the Epulorhiza 2 group were found, while the latter were more typical of drier habitats, where they were dominant. The Ceratobasidiaceae fungi, also isolated in considerable numbers, were more dominant in habitats with moderate water supplies, which were also home to representatives of the Sebacinaceae, though these were isolated in smaller numbers. The great variability in the composition of the symbiotic fungi of orchids in the different habitats suggests that efforts to preserve orchids require an accurate knowledge of orchid habitats, including data on potential fungal partners