title: Evolution of three Pyrenophora cereal pathogens: recent divergence, speciation and evolution of non-coding DNA.
abstract: Three of the most important fungal pathogens of cereals are Pyrenophora tritici-repentis, the cause of tan spot on wheat, and Pyrenophora teres f. teres and Pyrenophora teres f. maculata, the cause of spot form and net form of net blotch on barley, respectively. Orthologous intergenic regions were used to examine the genetic relationships and divergence times between these pathogens. Mean divergence times were calculated at 519 kya (±30) between P. teresf. teres and P. teresf. maculata, while P. tritici-repentis diverged from both Pyrenophora teresforms 8.04 Mya (±138 ky). Individual intergenic regions showed a consistent pattern of co-divergence of the P. teresforms from P. tritici-repentis, with the pattern supported by phylogenetic analysis of conserved genes. Differences in calculated divergence times between individual intergenic regions suggested that they are not entirely under neutral selection, a phenomenon shared with higher Eukaryotes. P. tritici-repentis regions varied in divergence time approximately 5-12 Mya from the P. teres lineage, compared to the separation of wheat and barley some 12 Mya, while the P. teresf. teres and P. teresf. maculata intergenic region divergences correspond to the middle Pleistocene. The data suggest there is no correlation between the divergence of these pathogens the domestication of wheat and barley, and show P. teresf. teres and P. teresf. maculata are closely related but autonomous. The results are discussed in the context of speciation and the evolution of intergenic regions.
authors: Department of Environment and Agriculture, Curtin University, Bentley, Perth, Western Australia 6102, Australia. srellwood@gmail.com
authors: Simon R
authors: SR
authors: Ellwood
authors: Rob A
authors: RA
authors: Syme
authors: Caroline S
authors: CS
authors: Moffat
authors: Richard P
authors: RP
authors: Oliver
mesh_terms: D001203:Ascomycota / Q000145:classification / Q000235:genetics*; D001483:Base Sequence; D004271:DNA, Fungal / Q000235:genetics; D021901:DNA, Intergenic / Q000235:genetics; D019143:Evolution, Molecular; D049810:Genetic Speciation; D016681:Genome, Fungal / Q000235:genetics; D059014:High-Throughput Nucleotide Sequencing; D001467:Hordeum / Q000382:microbiology*; D008969:Molecular Sequence Data; D058885:Multilocus Sequence Typing; D016533:Mycological Typing Techniques; D010802:Phylogeny; D010935:Plant Diseases / Q000382:microbiology*; D017422:Sequence Analysis, DNA; D013997:Time Factors; D014908:Triticum / Q000382:microbiology*
chemical_list: D004271:DNA, Fungal; D021901:DNA, Intergenic