الفهرس 
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Abstract
The genus Phleum L., (Timothy grasses) is a member of tribe Aveneae, in subfamily Poaceae-Pooideae. It comprises 15 species of annual or perennial plants native to the Old World and found in almost all non-tropical countries. The wide patterns of distribution, considerable variation in morphological traits, and the evident presence of polyploidy in the species renderd Phleum a potentially valuable subject for the current study in phylogenetic inference and phenetic re-assessment. At the Virginia Tech University, USA, it was possible to construct the first comprehensive phylogeny for the entire genus using nucleotide sequences of the nuclear internal transcribed spacer (ITS) and plastid trnL-F and psbJ-petA intergenic spacers based on maximum parsimony and model-based maximum Likelihood and Bayesian inference methods. Thirteen species and six subspecies with multiple accessions were included in the molecular work. Genomic DNA isolation, PCR amplifications, DNA sequencing, sequence editing and alignments were carried out. Further and analyzed phylognetically, in addition cloning of the amplified nuclear segments of the polyploidy species were conducted when multiple peaks were detected to separate the alleles of the nuclear genomic region. The separation of section Phleum from the rest is in agreement with the classifications proposed by the majority of the earlier taxonomists. Section Maillea (comprising only P. crypsoides and its subsp. sardoum) was represented in the analysis by nine specimens and showed complete cohesion as they constituted a separate group 6, which was deeply immersed among the low-level groups of group B1 closest to some representatives of section Achnodon. Each of the two remaining sections, Achnodon and Chilochloa, was split almost equally between groups B1 and B2. Even within the subordinate groups 4-9, the accessions representing the species of these two sections are mixed together. An improved circumscription of these two sections seems to warrant a more detailed study covering a wider range of the plants’ characters recorded from a larger number of accessions than that used in the present study.