BACKGROUND AND AIMS: It is well known that genome size differs among species. However, information on the variation and dynamics of genome size in wild populations and on the early phase of genome size divergence between taxa is currently lacking. Genome size dynamics, heritability and phenotype effects are analysed here in a wild population of Festuca pallens (Poaceae). METHODS: Genome size was measured using flow cytometry with DAPI dye in 562 seedlings from 17 maternal plants varying in genome size. The repeatability of genome size measurements was verified at different seasons through the use of different standards and with propidium iodide dye; the range of variation observed was tested via analysis of double-peaks. Additionally, chromosome counts were made in selected seedlings. KEY RESULTS AND CONCLUSIONS: Analysis of double-peaks showed that genome size varied up to 1.188-fold within all 562 seedlings, 1.119-fold within the progeny of a single maternal plant and 1.117-fold in seedlings from grains of a single inflorescence. Generally, genome sizes of seedlings and their mothers were highly correlated. However, in maternal plants with both larger and smaller genomes, genome sizes of seedlings were shifted towards the population median. This was probably due to the frequency of available paternal genomes (pollen grains) in the population. There was a stabilizing selection on genome size during the development of seedlings into adults, which may be important for stabilizing genome size within species. Furthermore, a positive correlation was found between genome size and the development rate of seedlings. A larger genome may therefore provide a competitive advantage, perhaps explaining the higher proportion of plants with larger genomes in the population studied. The reason for the observed variation may be the recent induction of genome size variation, e.g. by activity of retrotransposons, which may be preserved in the long term by the segregation of homeologous chromosomes of different sizes during gametogenesis.

• MeSH
• chromozomy rostlin genetika   MeSH
• DNA rostlinná genetika   MeSH
• fenotyp MeSH
• Festuca genetika   MeSH
• genetická variace * MeSH
• genom rostlinný * MeSH
• polyploidie * MeSH
• průtoková cytometrie MeSH
• semenáček genetika   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• DNA rostlinná MeSH

BACKGROUND AND AIMS: Plant evolution is well known to be frequently associated with remarkable changes in genome size and composition; however, the knowledge of long-term evolutionary dynamics of these processes still remains very limited. Here a study is made of the fine dynamics of quantitative genome evolution in Festuca (fescue), the largest genus in Poaceae (grasses). METHODS: Using flow cytometry (PI, DAPI), measurements were made of DNA content (2C-value), monoploid genome size (Cx-value), average chromosome size (C/n-value) and cytosine + guanine (GC) content of 101 Festuca taxa and 14 of their close relatives. The results were compared with the existing phylogeny based on ITS and trnL-F sequences. KEY RESULTS: The divergence of the fescue lineage from related Poeae was predated by about a 2-fold monoploid genome and chromosome size enlargement, and apparent GC content enrichment. The backward reduction of these parameters, running parallel in both main evolutionary lineages of fine-leaved and broad-leaved fescues, appears to diverge among the existing species groups. The most dramatic reductions are associated with the most recently and rapidly evolving groups which, in combination with recent intraspecific genome size variability, indicate that the reduction process is probably ongoing and evolutionarily young. This dynamics may be a consequence of GC-rich retrotransposon proliferation and removal. Polyploids derived from parents with a large genome size and high GC content (mostly allopolyploids) had smaller Cx- and C/n-values and only slightly deviated from parental GC content, whereas polyploids derived from parents with small genome and low GC content (mostly autopolyploids) generally had a markedly increased GC content and slightly higher Cx- and C/n-values. CONCLUSIONS: The present study indicates the high potential of general quantitative characters of the genome for understanding the long-term processes of genome evolution, testing evolutionary hypotheses and their usefulness for large-scale genomic projects. Taken together, the results suggest that there is an evolutionary advantage for small genomes in Festuca.

• MeSH
• Festuca genetika   MeSH
• fylogeneze MeSH
• genom rostlinný * MeSH
• molekulární evoluce * MeSH
• polyploidie MeSH
• retroelementy MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• retroelementy MeSH