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Genome Organization and Evolution in Genus Quercus (Fagaceae): Special Attention to Two European White Oaks Quercus petraea (Matt.) Liebl. and Q. robur L.

Quercus is a fascinating tree genus. Even on the face value, oaks are impressive because of their immense size and very long lifespan. TOak trees are of enormous economical, antrophological and ecological significance. With around 600 species this is the most species-rich genus in the family Fagaceae, which in whole comprises around 1000 species. Oaks are widespread from the temperated zone of the Northern Hemisphere to Mediterranean and subtropical zone. The oaks probably represent the most extensively studied genus by different specialists, such as population geneticists, tree breeders, sylviculturists, cytogeneticists, molecular biologists and plant physiologists. The tremendous morphological diversity of oaks varies from deciduous to evergreen trees and shrubs. There are common cases where pairs of oaks show clear morphological and ecological differences but are poorly differentiated on genetic level, as for example the most popular and predominant European white oaks, Q. petraea (Matt.) Liebl. and Q. robur L. They can hybridize in nature, as many pairs of oak species of different taxonomical sections, and still remain distinct morphologically. Therefore, the concept of biological species has been questionable as far as oaks are concerned, and a new concept of multispecies or ecological species has been proposed. This rewiev has been restricted to Q. petraea and Q. robur with respect to interspecific hybridization and gene flow for oak genome structure. However, these two oaks, and other oak species in general, are still insufficiently explored in terms of molecular structure of their genomes. The present data will give a valuable image of oak genome structure, which will serve us guidelines in further research. Cytogenetic data is also scarce, but progress has been made recently in terms of chromosome number and genome size determination, karyotyping (after Giemsa C-banding and fluorochrome banding) and mapping of ribosomal DNA, retrotransposon-like sequences and telomeres on chromosomes of some oak species. Chromosomal and DNA maarkers are used across the genus Quercus to infer aout karyotype/genome evolution and speciation. Also, a first comprehensive genetic map is given for Q. roubur. In spite of the large volumes of literature published on oaks, this woody group of plants still requires further exploration.

evolution, gene flow, genome organization, genetic differentiation, interspecific hybridization, karyotypes, molecular markers, systematics, phylogeny, Quercus

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