The long-term utility of DNA banks is predicated on the stability of DNA during storage. The quality and yield of DNA extracted from seeds from four garden species, which varied in age from 1 to 135 years old, was used to examine the early stages of DNA degradation. Seeds that were 70 years old yielded high molecular weight DNA, which permitted amplification of a 650 bp segment of the internal transcribed spacer (ITS) region of the nuclear ribosomal DNA and a 487 bp segment of the plastid-encoded large subunit of rubisco (rbcL). DNA extracted from seeds estimated to be about 135 years old was degraded, but still permitted amplification when routine extraction procedures were used. The rbcL sequences obtained from c. 135-year-old cucurbit seed DNA were consistent with species identifications based on seed morphological features; however, ITS sequences from the same samples were determined to be of fungal origin. A comparison of our results with studies of DNA stability in leaf specimens suggested that DNA degraded within both tissues, but perhaps more slowly within seeds. Evidence that high-quality DNA can be extracted from old, non-viable seeds expands the utility of seed banks in preserving genetic resources.

Free-floating Ulva L. biomass in the eutrophic brackish ‘Veerse Meer’ lagoon (southwest Netherlands) consists of four morphologically identified species: U. curvata (Kützing) De Toni, U. lactuca L., U. rigida C. Agardh and U. scandinavica Bliding. U. curvata could be recognized easily because of the characteristic central cavity in the holdfast of the attached plants, the arrangement of cells in rows and the single pyrenoid in each cell. U. rigida was distinguished by the thick thallus and the large number of pyrenoids. The Veerse Meer isolate, however, was slightly different from the isolate from the Oosterschelde estuary (the Netherlands). U. lactuca and U. scandinavica showed a high degree of overlap in thallus thickness and cell size, but U. scandinavica usually possessed more pyrenoids. However, doubts have frequently been expressed about the use of some morphological characters in Ulva taxonomy. To determine the validity of such characters in the identification of Ulva species, the morphological variation within and between morphological species was recorded and a molecular data set generated. To detect possible ecophysiological differences between species, optimum temperatures and salinities for growth were determined experimentally. The sequences of the nuclear ribosomal DNA internal transcribed spacer 2 (ITS2) and flanking regions of U. lactuca, U. rigida and U. scandinavica from the Veerse Meer were all identical, but differed from that of U. rigida from the Oosterschelde estuary. Ulva species from the Veerse Meer were most closely related to U. armoricana and U. rigida from Brittany (2·9% and 3·5% divergence respectively); the difference between U. rigida from the Veerse Meer and from the Oosterschelde estuary was 7·5%. Rooted trees, based on a comparison of these sequences with sequences of other Ulva and Enteromorpha species obtained from the literature, using Monostroma arcticum as outgroup, suggested that Ulva is paraphyletic with respect to Enteromorpha. The optimum temperature for growth of U. curvata was 25 °C; for all other species it was 10 °C. The optimum salinity for growth was 30 °C for all isolates. It is concluded that U. lactuca, U rigida and U. scandinavica from the Veerse Meer are all members of one highly polymorphic species.

Molecular phylogenetic relationships among sexually isolated subpopulations (syngens) of the morphologically defined volvocacean flagellate Pandorina morum (O. F. Müller) Bory are inferred from sequences of the internal transcribed spacer regions (ITS-1 and ITS-2) of the nuclear ribosomal DNA repeats. The resolved phylogenetic lines are composed of strains with very similar sets of traditional characters, such as zygote aggregation pattern, chromosome number and cell division timing, and are correlated with the distribution pattern of the xanthophyll loroxanthin [(3R,3′R,6′R)-β,ε-carotene-3,19,3′-triol]. Thus, loroxanthin, a phylogenetic character within the Volvocales, is also of value at the infraspecific level in P. morum, a morphologically uniform species complex, within the Volvocales.

The utility of rDNA internal transcribed spacer (ITS) sequences for separating species of Ulva along the North Brittany coast of France was investigated. Particular attention was paid to the Ulva species responsible for ‘green tides’. Floating thalli are difficult to identify due to fragmentation and it was not clear at the outset whether one or more species of Ulva might be contributing to the green tide phenomenon. Results show that ITS sequences are good markers for Ulva species and that the Lannion Bay green tide taxon is a previously unrecognized species that can also be identified on morphological grounds. We found that ITS type did not necessarily correspond to the initial identification of a specimen based on morphological features, due to the lack of good diagnostic characters. This survey highlights the need for a more intensive survey of Ulva populations along European coasts. Once ITS groups can be recognized, quick screening assays can be developed to aid morphological identification.

Sixty-two isolates of Pisolithus were obtained from a carpophore population collected from a 90-km2 area of New South Wales, Australia. Random amplified polymorphic DNA (RAPD) analysis was used initially to screen isolates for variation, and restriction fragment length polymorphism (RFLP) analysis of the internal transcribed spacer (ITS) region and ITS sequence analysis were subsequently performed on selected isolates. ITS–RFLP and ITS sequence analysis indicated that two isolates (LJ07 and WM01) from different sites were considerably different from all other isolates, a strict consensus tree generated by bootstrap analysis of sequence data strongly suggesting that isolates LJ07 and WM01 represent a separate Pisolithus species. Although the general morphology of carpophores and basidiospores of the majority of collected isolates was consistent with previous descriptions of P. tinctorius (Pers.) Coker and Couch, basidiospore characteristics suggest that isolates LJO7 and WMO1 might represent a Pisolithus species distinct from P. tinctorius and the previously described Australian species, P. microcarpus (Cooke & Massee) G. Cunn.