Articles
Molecular genetic analysis of Pseudoperonospora humuli populations in hop growing areas in the Czech Republic
Article number
1328_7
Pages
55 – 62
Language
English
Abstract
Hop downy mildew Pseudoperonospora humuli is a major fungal hop pathogen of worldwide importance, causing severe yield and quality losses.
Previous studies of P. humuli in hop growing areas of the United States showed only little genetic variability within the fungal population.
The character of Czech P. humuli populations was unknown prior to this work, therefore, we studied the genomic and population diversity by molecular methods.
Isolates of P. humuli have been collected during spring starting from commercial fields in the ‘Saaz’ hop growing region over several seasons.
Basal spikes from all Czech hop growing areas were collected in 2018 mainly from susceptible cultivars.
We analyzed sequential variability of internal transcribed spacer of nuclear ribosomal DNA (ITS) region, β-tubulin gene(β-tub), and the cytochrome c oxidase (cox) cluster (cox2, cox2–cox1 spacer and cox1). Substitution frequencies varied from 0.75% for nuclear ITS regions to 3.14% mitochondrial cox cluster sequences.
Phylogenetic analyses showed there was only little sequence variability within Czech P. humuli isolates across studied population localities and years.
We also used 25 simple sequence repeats (SSR) markers for the evaluation of genetic variation.
Only ten primer combinations amplified SSR markers and all amplified SSR markers were monomorphic.
Therefore, genetic structure of Czech P. humuli populations differed little, and it can be suggested that P. humuli populations have clonal character in the Czech Republic.
Previous studies of P. humuli in hop growing areas of the United States showed only little genetic variability within the fungal population.
The character of Czech P. humuli populations was unknown prior to this work, therefore, we studied the genomic and population diversity by molecular methods.
Isolates of P. humuli have been collected during spring starting from commercial fields in the ‘Saaz’ hop growing region over several seasons.
Basal spikes from all Czech hop growing areas were collected in 2018 mainly from susceptible cultivars.
We analyzed sequential variability of internal transcribed spacer of nuclear ribosomal DNA (ITS) region, β-tubulin gene(β-tub), and the cytochrome c oxidase (cox) cluster (cox2, cox2–cox1 spacer and cox1). Substitution frequencies varied from 0.75% for nuclear ITS regions to 3.14% mitochondrial cox cluster sequences.
Phylogenetic analyses showed there was only little sequence variability within Czech P. humuli isolates across studied population localities and years.
We also used 25 simple sequence repeats (SSR) markers for the evaluation of genetic variation.
Only ten primer combinations amplified SSR markers and all amplified SSR markers were monomorphic.
Therefore, genetic structure of Czech P. humuli populations differed little, and it can be suggested that P. humuli populations have clonal character in the Czech Republic.
Publication
Authors
M. Werschallová, J. Patzak, A. Henychová
Keywords
hop downy mildew (Pseudoperonospora humuli), population genetic diversity,internal transcribed spacer (ITS) rDNA regions, β-tubulin gene (β-tub), cytochrome c oxidase (cox) cluster, sequence variability, SSR molecular markers, phylogenetic analysis
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