@ARTICLE{TreeBASE2Ref24300, author = {Miloslav Kitner and Ales Lebeda and Rahul Sharma and Fabian Runge and Petr Dvoř?k and Ali Tahir and Young-Joon Choi and Bo?ena Sedl?kov? and Marco Thines}, title = {Coincidence of virulence shifts and population genetic changes of Pseudoperonospora cubensis in the Czech Republic }, year = {2015}, keywords = {Cucurbit downy mildew; Genetic diversity; Host and virulence shift; Multilocus sequencing; Population structure; Pseudoperonospora cubensis}, doi = {}, url = {http://}, pmid = {}, journal = {Plant Pathology}, volume = {}, number = {}, pages = {}, abstract = {Pseudoperonospora cubensis is an oomycete pathogen causing downy mildew disease on a variety of Cucurbitaceae, and has recently re-emerged as a destructive disease on crops in this family, mainly on cucumber and squash. Multilocus sequence analysis (MLSA) of four mitochondrial and two nuclear DNA regions was used to detect changes in the genetic structure of P. cubensis populations occurring in the Czech Republic that might be associated with recently reported shifts in virulence. Tajima?s D neutrality test was significant for nuclear loci but non-significant for all mitochondrial loci. This inconsistency probably stems from generally low amounts of substitutions and domain-driven heterogeneity in the distribution of mutations. The analyzed sample set contains 67 P. cubensis isolates collected during 1995 to 2012 in the Czech Republic and some other European countries. Sequence analyses revealed differences and changes in the genetic backgrounds of P. cubensis isolates sampled both before and after 2009. While all isolates sampled before 2009 exhibited the genotype of the subspecies of Clade II, and were collected from cucumber; all samples collected from other hosts belonged to Clade I (P. cubensis sensu stricto) or were sampled from 2009 onwards. In addition, 67.16% of all post-2009 isolates from Clade II had two heterozygous positions in their nrITS sequence, providing hints for sexual reproduction and/or a mutational origin. Thus, our results indicate that apart from the rise in prevalence of Clade I strains, the change in the genetic structure of P. cubensis populations may be linked with a hybridisation or, less likely, mutation event that rendered strains able to infect a broader spectrum of host species. } }

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