Pseudoperonospora humuli might be an introduced species in Central Europe with low genetic diversity but high distribution potential

“Jumping Jack”: Genomic Microsatellites Underscore the Distinctiveness of Closely Related Pseudoperonospora cubensis and Pseudoperonospora humuli and Provide New Insights Into Their Evolutionary Past

“…To date, only three studies (Chee et al, 2006;Gent et al, 2019;Kitner et al, 2021) have analyzed the P. humuli diversity using a population genetics approach. Chee et al (2006) suggested differences in the population structures and reproduction modes due to climate in Oregon and Washington, using the RAPD markers for genotyping on a local scale.…”

“…Gent et al (2019) used genotyping-by-sequencing of the 2010 and 2011 pathogen populations from those same U.S. states to discover limited genetic diversity in P. humuli, in line with repeated inbreeding in this homothallic oomycete. Kitner et al (2021) tested crossamplification of short sequence repeats (SSRs) developed for P. cubensis (Wallace and Quesada-Ocampo, 2017) on the P. humuli collected from Central Europe around the Alps. They also developed five SSRs that were more polymorphic than the other tested, suggesting higher genetic uniformity of P. humuli in Europe than in North America and prompting their hypothesis of the pathogen being introduced to Europe (Kitner et al, 2021).…”

“…Kitner et al (2021) tested crossamplification of short sequence repeats (SSRs) developed for P. cubensis (Wallace and Quesada-Ocampo, 2017) on the P. humuli collected from Central Europe around the Alps. They also developed five SSRs that were more polymorphic than the other tested, suggesting higher genetic uniformity of P. humuli in Europe than in North America and prompting their hypothesis of the pathogen being introduced to Europe (Kitner et al, 2021). Comparatively, several molecular approaches were used for population biology of P. cubensis (Quesada-Ocampo et al, 2012;Polat et al, 2014;Kitner et al, 2015;Naegele et al, 2016;Thomas et al, 2017a;Wallace and Quesada-Ocampo, 2017).…”

Genetic characterization of downy mildew resistance from the hop (Humulus lupulus L.) line USDA 64035M

“…With regard to the pathogenicity of P. humuli in hop, there has been no reported occurrence of any form of pathogenic variation among isolates associated with host genotype or geographic region (Purayannur et al, 2021;Royle & Kremheller, 1981). Pseudoperonospora humuli has limited genetic diversity worldwide, consistent with clonal reproduction or a high degree of selfing due to homothallism (Gent et al, 2017(Gent et al, , 2019Kitner et al, 2021;Summers et al, 2015;Wallace & Quesada-Ocampo, 2017). Earlier studies have suggested that DM resistance (DMR) is under polygenic control (multiple genes with small effects) in hop (Henning et al, 2015;Parker, 2007).…”

The impact of climate change on disease in wild plant populations and communities

“…There is more information for wheat blast caused by Triticum pathotypes of Magnaporthe oryzae (Yoshida et al, 2016) where weather-based infection risk models have been developed for predicting outbreaks in the USA (Cruz et al, 2016), but these are not projected forward for climate change scenarios. In the last decade there have been many serious incursions of downy mildew pathogens into horticultural crops from related wild species (Ben-Naim et al, 2018;Kitner et al, 2021;Pyne et al, 2018), often as invasive species. Initial problems in species delimitation (Görg et al, 2017;Thines et al, 2019Thines et al, , 2020 hindered attempts to react to such incursions.…”