• Grasses;
  • taxonomy;
  • DNA base composition;
  • denaturation;
  • genome evolution


Intragenomic base composition heterogeneity was investigated in 35 species of the grass family Poaceae, using high-resolution thermal denaturation of DNA to produce base composition distributions. These show a pattern of peaks and shoulders which represent overlapping components of discrete base composition and provide a ‘fingerprint’ of the genome of a species. Quantitative comparison of distribution by distance matrix and cluster analysis supported traditional groupings within the Poaceae and allowed clarification of previous artificial relationships between taxa. The technique was most successful in distinguishing between taxa within subfamily, from tribal to generic level. Use of an absolute measure of all sequences present in a genome avoids problems inherent in commonly used DNA/DNA hybridization methods for determining homology. The non-random distribution of DNA base composition components conserved among related genomes is discussed in relation to chromosome architecture and to exploitation of the gene pool of the Poaceae.