What happens to your Powdery Mildew Samples once they arrive in the lab?

To begin, I need to plant some Baudin seed to use in the lab. The seed is planted in a substance called vermiculite, not soil. The vermiculite is a lightweight, highly absorbent mineral and is used in thousands of applications including potting soils and grow mixes.

The lights in the room are on a timer so that they are on during the day and turn off at night, mimicking the conditions in the field. The Baudin seeds are then given water and left to grow under lights in a temperature controlled room. I give them additional water every 2-3 days.

While I'm waiting for the plants to grow I need to prepare some agar plates. Later, I will use the plates to keep the different mildew samples separate from each other in the laboratory. I measure out some agar powder and add it to water. The agar must be sterilised before use to remove bacteria and other fungi. It is placed in an oven where it is heated to 120°C for 20 minutes and then poured into petri dishes. As the agar cools it forms a gel.

The leaves are then inserted into the agar gel in the petri dishes. The dishes are sealed with tape to keep the isolates separate from one another. They are then left to grow. Now I can start using your samples. I cut leaf pieces from the Baudin I have grown and place them at the bottom of a plastic pipe. I take your sample from the tube and shake it over the top of the pipe. Spores of the fungi move from your sample onto my fresh Baudin leaves.

To process the swabs I cut off a small piece of the cotton tip and place it into a separate tube. In about 7 to 10 days, the fluffy mildew begins to appear on the infected leaves. Now I can start to get DNA from the isolates. Using the plates I prepared earlier, I cut away a single fluffy pustule and place it into a small tube.

A pipette is an instrument used to measure out very small volumes of liquids. I use my pipette to add several different liquids into the tubes. The tubes are then put into a machine which heats and cools the liquids in a programmed order. This process causes a reaction which greatly increases the amount of DNA in each tube.

Once the reaction is complete, I use a method called gel electrophoresis to look at the quality and quantity of my DNA. I use my pipette to suck up a tiny amount of DNA and load it into small wells in a gel. The gel is in a tank filled with a special liquid. After loading, the tank is subject to an electric current which causes the DNA to move down through the gel. The pieces of DNA move according to their length. Longer pieces move slower, smaller pieces move faster.

After about 60 minutes the gel is ready to use. I take the gel to a special machine which shines an ultra violet light through the gel. The machine puts out a picture which allows me to quantify and qualify the DNA.

Afterwards, I submit the DNA for sequencing. This allows me to check for mutations which cause resistance towards some fungicides. This is an example of the DNA sequence from one of the isolates.

So that’s what happens to your Powdery Mildew Samples once they arrive in the lab. Thanks so much for your contribution to my work.