High levels of genetic and genotypic diversity in field populations of the barley pathogen Ramularia collo-cygni
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High levels of genetic and genotypic diversity in field populations of the barley pathogen Ramularia collo-cygni R. L. Hjortshøj & A. R. Ravnshøj & M. Nyman & J. Orabi & G. Backes & H. Pinnschmidt & N. Havis & J. Stougaard & E. H. Stukenbrock
Accepted: 21 November 2012 / Published online: 14 December 2012 # KNPV 2012
Abstract The ascomycete pathogen Ramularia collocygni causes Ramularia leaf spot (RLS) on barley. Although R. collo-cygni is considerd an emerging disease of barley, little is known about genetic diversity or population genetic structure of this pathogen. We applied a set of polymorphic AFLP (Amplified Fragment Length Polymorphism) markers to investigate population genetic structure in two Northern European populations of R. collo-cygni. The distribution of AFLP alleles revealed low levels of population subdivision and high levels of genetic diversity at both locations. Our analyses included 87 isolates and of
these 84 showed a unique genotype pattern. The genetic structure of populations in Scotland and Denmark is highly similar and we find no evidence of population sub-division. An analysis of molecular variance was used to show that 86 % of the variance is attributable to within field genetic variance. In spite of the high levels of genetic and genotypic diversity in the R. collo-cygni populations, we find significant evidence of linkage disequilibrium among the AFLP alleles using a multilocus analysis. We propose that the high levels of genotypic diversity and the lack of population differentiation result from considerable
R. L. Hjortshøj (*) Sejet Plantbreeding, Nørremarksvej 67, 8700 Horsens, Denmark e-mail: [email protected]
J. Orabi : G. Backes Department of Agriculture and Ecology, Copenhagen University, Thorvaldsensvej 40, 1871 Frederiksberg, Denmark
R. L. Hjortshøj : J. Stougaard Department of Molecular Biology, Aarhus University, Gustav Wieds Vej 10c, 8000 Aarhus, Denmark A. R. Ravnshøj Department of Plant Biology and Biotechnology, Copenhagen University, Thorvaldsensvej 40, 1871 Frederiksberg, Denmark M. Nyman : N. Havis Crop and Soil Research Group, Scottish Rural University College, W. Mains Road, Edinburgh, UK
H. Pinnschmidt Department of Integrated Pest Management, Aarhus University, Forsøgsvej 1, 4200 Slagelse, Denmark
E. H. Stukenbrock Max Planck Institute for Terrestial Micropbiology, Karl von Frischstraße 10, 35043 Marburg, Germany
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levels of gene flow between populations most likely mediated by seed borne dispersal of inoculum. Keywords Ramularia collo-cygni . Population genetics . AFLP . Diversity index . Genetic differentiation . Linkage disequilibrium
Introduction The ascomycte fungus Ramularia collo-cygni causes the disease Ramularia leaf spot (RLS) on barley (Hordeum vulgare L.). RLS is considered an emerging disease of barley with increasing importance to agriculture in Northern and Central Europe (Walters et al. 2008). Though R. collo-cygni was first described in 1893 (Cavara 1893), it was not until the late 1980’s that widespread presence of the pathogen was report
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