title: Phylogeny of an Albugo sp. infecting Barbarea vulgaris in Denmark and its frequency of symptom development in natural populations of two evolutionary divergent plant types.
abstract: The oomycete Albugo candida has long been considered a broad spectrum generalist pathogen, but recent studies suggest that it is diverged into several more specialized species in addition to the generalist Albugo candida sensu stricto. Whereas these species cause the disease white blister rust in many crucifer plants, asymptomatic endophytic infections may be important in the epidemiology of others. One of the plant species attacked by Albugo sp. is the wild crucifer Barbarea vulgaris ssp. arcuata, which is diverged into two phytochemically and genetically different types with different geographical distributions in Europe. These were previously shown to differ strongly in propensity to develop white rust upon controlled infections in the greenhouse. Here, we analyse the phylogenetic relatedness of this local Albugo sp. field isolate to other species and lines of Albugo spp., including others collected on B. vulgaris. We further ask whether the difference in incidence of white rust between the two types of B. vulgaris are also expressed in natural populations. Phylogenetically, the local Albugo sp. field isolate clustered tightly together with previously analysed samples from B. vulgaris, supporting that the Albugo sp. infecting B. vulgaris may indeed be an independent specialized species. White blister rust and Albugo DNA was only detected in two populations of the plant type that frequently develops symptoms upon controlled inoculations. The lack of white rust and Albugo sp. DNA in the other plant type may be due to either resistance, preventing infection, or asymptomatic infection of other tissues than leaves, which we analysed.
authors.affiliation: Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, 1958 Frederiksberg, Denmark.
authors.forename: Tamara
authors.initials: T
authors.lastname: van Mölken
authors.affiliation: Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, 1958 Frederiksberg, Denmark.
authors.forename: Christine
authors.initials: C
authors.lastname: Heimes
authors.affiliation: Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, 1958 Frederiksberg, Denmark. Electronic address: tpha@plen.ku.dk.
authors.forename: Thure P
authors.initials: TP
authors.lastname: Hauser
authors.affiliation: Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, 1958 Frederiksberg, Denmark.
authors.forename: Thomas
authors.initials: T
authors.lastname: Sundelin
mesh_terms: D031216:Barbarea / Q000382:microbiology*; D016000:Cluster Analysis; D004271:DNA, Fungal / Q000737:chemistry / Q000235:genetics; D003718:Denmark; D008969:Molecular Sequence Data; D009868:Oomycetes / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification; D010802:Phylogeny; D010935:Plant Diseases / Q000382:microbiology*; D017422:Sequence Analysis, DNA
chemical_list: D004271:DNA, Fungal
keywords: Asymptomatic infections; Incidence; Natural plant populations; Oomycete; White blister rust