Interactive impacts of a herbivore and a pathogen on two resistance types of Barbarea vulgaris (Brassicaceae).

It is well known that pathogens and arthropod herbivores attacking the same host plant may affect each other. Little is known, however, about their combined impact on plant fitness, which may differ from simple additive expectations. In a 2-year common garden field experiment, we tested whether the pathogen Albugo sp.

Multiple hydroxyphenethyl glucosinolate isomers and their tandem mass spectrometric distinction in a geographically structured polymorphism in the crucifer Barbarea vulgaris.

Two distinct glucosinolate (GSL) chemotypes (P and G-types) of Barbarea vulgaris (Brassicaceae) were known from southern Scandinavia, but whether the types were consistent in a wider geographic area was not known. Populations (26) from Eastern and Central Europe were analyzed for GSLs in order to investigate whether the two types were consistent in this area. Most (21) could be attributed to one of the previously described GSL profile types, the P-type (13 populations) and the G-type (8 populations), based on differences in the stereochemistry of 2-hydroxylation, presence or absence of phenolic glucobarbarin derivatives, and qualitative differences in indole GSL decoration (tested for a subset of 8+6 populations only).

Different geographical distributions of two chemotypes of Barbarea vulgaris that differ in resistance to insects and a pathogen.

The interactions of plants with herbivores and pathogens have been suggested to drive the evolution of resistances in plants and in some cases new lineages and taxa. However, such divergence may require reproductive isolation, e.g.

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.

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.