Diversity, evolution, and ecology of white blister rusts
Marco Thines
Biodiversity and Climate Research Centre Frankfurt, Germany
White blister rusts are a cosmopolitan group of obligate biotrophic oomycetes and are
not related to true fungi, but to diatoms and other members of the Straminipila. While the
host spectrum of the white blister rusts encompasses a wide range of flowering plants,
recent investigations have revealed that some white blister rusts are highly host specific.
Until five years ago it was believed that the Brassicaceae are parasitised by a single
species, Albugo candida, which has a broad host range, encompassing several hundred
species in this family. Recent molecular and morphological studies have revealed that in
addition to Albugo candida, which has indeed a very broad host range, extending even
to related families like Cleomaceae and Capparaceae, several specialized species exist.
These include a specialized species on Arabidopsis thaliana, at least four distinct
species in the genus Cardamine, and a specialized species on Barbarea. Based on the
current knowledge, it seems likely that in Brassicaceae alone a few dozen species await
their discovery. This could also extend to predominantly endophytic species, as we could
recently demonstrate that Albugo candida can infest host plants asymptomatically and
can potentially be transmitted vertically to the next generation of host plants. Potential
factors influencing pathogenic development of asymptomatic endophytes will be shortly
discussed on the example of two oomycete pathogens (Protobremia sphaerosperma
and Pustula obtusata) infecting goatsbeard (Tragopogon pratensis agg.).
