Article Images: m936cover

 

On the cover: Infection of Arabidopsis thaliana with Peronospora parasitica, the causal agent of downy mildew. Shown is the base of a leaf stained with trypan blue and cleared for observation, six days after infection. The large spheres are oosporangia and oospores. The branching filaments are asexual conidiophores. Downy mildew is one of the promising pathogen systems in Arabidopsis. Photomicrograph by Terrence Delaney. See the article by Uknes et al. on page 692 of this issue.