My Research

Koch's Postulates

Activation of isolates was successful with almost all isolates so I am now able to move on to carry out Kochs postulates with them. The aim of Koch's postulates is to confirm a diagnosis that a particular suspected organism is causing the observed disease. The steps were first described by Robert Koch in 1882 and later added to by Erwin F Smith in 1905. The steps are as follows:

1. determine the suspected pathogen is consistently associated with the disease
2. isolate the suspected pathogen from the diseased plant and grow it in pure culture on artificial media and describe it.
3. Inoculate the isolated organism onto a healthy plant of the same species to see if it causes the same disease symptoms.
4. Re-culture the pathogen and determine that it is the same as the original isolate.

Steps one and two have already been completed so I am now going to work on steps 3 and 4.

Isolate activation

I am hoping to 'activate' some isolates by inoculating them into rhododendrons and then re-isolating them from the plant after infection has occurred in an attempt to remind the isolates how to be virulent. Some times we have isolates that have been maintained for so long in culture that they start to behave strangely or they stop sporulating for example. This is a technique to re-activate them before using them in experiments.

Soil inoculation relative success

I have been trying to inoculate rhododendron roots with Phytophthora spp for a while and Kim and I have tried several methods that are reported in the literature. I set my latest trial up in the mist chamber to maximise the water availability and finally I seem to have symptoms all be it in only one rep out of three and on only one species out of 7 but never the less I have symptoms yay. See the wilting plant on the right compared with happy plant on the left.

Detached leaf experiment

I ran another repeat of my detached leaf inoculation where I dip inoculate leaves in zoospores suspension and incubate them without wounding for 2 weeks. I spent 8 hours on Labor Day doing this and it looks as though it hasn't worked. This is the fourth time I have set this experiment up and the other 3 times I got good data, although the trends don't exactly match what I expected at least the leaves got infected. This time I was meticulous so I can't figure out why only 9 leaves out of 150 developed lesions. Gah! At least this shows the expected trend but there are so many misses I can't really use this as quantitative data. Perhaps I can just note the observations. So disheartening.

twitter

In case you haven't already noticed I have joined twitter and I'm having my tweets posted to the gadget in the right column of this blog so if you want to get an insight into what I am doing on a daily basis this will contain little snippets. You can follow me on twitter - @claret84