Fluorescence In Situ Hybridization Protocol for Visualization of Oomycetes In Vitro and In Planta.

Fluorescence in situ hybridization enables the visualization of organisms in the environment without having to culture them. Here, we describe a FISH protocol to visualize oomycete structures (mycelia, sporangiophores, sporangia, and oospores) directly as well as from colonized plant material. The protocol utilizes organic compounds with low toxicities and does not require a permeabilization step. The protocol was used to visualize impatiens downy mildew Plasmopara destructor sporangiophores colonizing an Impatiens walleriana leaf.