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Genetics Section

Blattner, Frank R. [1], Jakob, Sabine S. [1], Meister, Armin [2].

Genome size evolution of Hordeum (Poaceae) analyzed in a phylogenetic context.

Genome size variation in plants is thought to be correlated with cytological, physiological, or ecological characters. However, conclusions drawn in several studies were often contradictory. To analyze nuclear genome size evolution in a phylogenetic framework, DNA contents of 134 accessions, representing all but one species of the barley genus Hordeum L., were measured by flow cytometry. The 2C DNA contents were in a range from 6.8510.67 pg in diploids (2n = 14) and reached up to 29.85 pg in hexaploid species (2n = 42). The smallest genomes were found in taxa from the New World, which became secondarily annual, while the largest diploid genomes occur in Eurasian annuals. Genome sizes within species or subspecies were relatively uniform and in polyploid taxa they equaled mostly the added sizes of their proposed progenitors or were slightly (1-5%) smaller. The analysis of ancestral genome sizes on the base of the phylogeny of the genus revealed lineages with decreasing and with increasing genome sizes. Correlations of intraspecific genome size variation with the length of vegetation period were found in H. marinum populations from Western Europe but were not significant within two species from southern South America. On a higher taxonomical level, i.e., for species groups or the entire genus, environmental correlations were absent. This could mostly be attributed to the superimposition of influences from life form changes, phylogenetic constraints, and population genetic parameters effective particularly during speciation events, which conceal ecogeographical correlations.


1 - Inst. of Plant Genetics and Crop Plant Research, Dept. of Taxonomy, Corrensstr. 3, Gatersleben, D-06466, Germany
2 - Inst. of Plant Genetics and Crop Plant Research, Dept. of Cytology, Gatersleben, D-06466, Germany

Keywords:
flow cytometry
genome size evolution
Hordeum
life form
phylogeny
population genetics
speciation.

Presentation Type: Paper
Session: 53-8
Location: Peruvian (Cliff Lodge)
Date: Wednesday, August 4th, 2004
Time: 2:45 PM
Abstract ID:78


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