Today I started the process of isolating Phytophthora from the soil and deceased plants from my summer experiments. I’ve plated roots before, but working with soil is new to me.
The intent is to take soil potentially infested with Phytophthora and flood it. This entices a release of zoospores, which should feel compelled to swim to the surface. When they arrive at the surface of the water there is bait waiting for them in the form of floating disks cut from Rhododendron catawbiense leaves. Any logical Phytophthora zoospore will see this as a great opportunity to have a party. The leaf disks are then moved to PARP plates–which is a selective media–no bacteria or true fungi allowed. As the organism grows in the plate it is identified. If all goes as planned it will turn out to be the very isolate of Phytophthora I used to inoculate the plants (or in the case of the negative controls there will be no Phytophthora present).