Smothered in white

White blister rust on Shepherd's purse

White blister rust on Shepherd’s purse

White blister rust is a disease that is mis-named as it is not actually caused by a rust fungus. The perpetrator is an oomycete. This group have traditionally been included in the fungi and have long been studied by mycologists but DNA evidence shows that oomycetes are more closely related to brown algae than to fungi or green plants. It was an oomycete that was responsible for the Irish potato famine in the 1800s.

 

 

Sporangia on stem and fruits

Sporangia on stem and fruits

White blister rust is common on Shepherds purse (Capsella bursa-pastoris) on campus and throughout Reading, especially on road sides. It develops into a thick white layer of sporangia that smother contorted and, often, enlarged parts of the plant. The causal organism, Albugo candida, is capable of infecting other members of the cabbage family. It was recently observed on Thale cress (Arabidopsis thaliana) near the Harborne Building.

About Fay Newbery

PhD student in the Plant Pathology Research Group.
This entry was posted in Brassicaceae, Flowering Plants, Galls, Plant Pathology Research Group, Plants and tagged , , , , . Bookmark the permalink.

2 Responses to Smothered in white

  1. I notice with interest that the fungus does not seem to have spread to the fruit – is this usual? I can see the potential selective advantage of the parasite allowing the host plant to continue it’s reproduction without damage but it suggests some kind of barrier between the pedicel and fruit.

    • Fay Newbery says:

      I’m afraid the oomycete isn’t that clever. The fruits get infected too. I’ve never looked inside an infected pod to see if the seeds appear normal but the pods are often extra large when infected.

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