Alternaria brassicicola and Erwinia carotovora Infections by Ryan Tillman

We have recently learned about necrotrophic pathogens, and how they kill the plant in order to gain nutrients, so this week we infected our plants with two types of necrotrophic pathogen. The first, Alternaria brassicicola, is a necrotrophic fungus, and the second, Erwinia carotovora, is a necrotrophic bacteria.

We started by preparing a petri dish to grow our Alternaria, and labeling each side for our two genotypes of plants, Col-0 and pad2. Next, to obtain the fungal spores for infection, we had to scrape them from growth plates, and, using potato dextrose, we transferred the spores into tubes.

We were supposed to find our spore concentration using a hemacytometer, but when our only one was broken, many of us were unable to do this, so we just continued on to the next step of placing 5 leaves of each genotype, Col-0 and pad2, on the designated sections in out petri dish.

For the next part of the lab, we went to the grow room, where we used a micropipette to transfer a small amount of the fungal spore/potato dextrose mixture from the tube onto the leaves. We sealed the petri dishes, and left them to grow for a few days.

When we returned to the lab after the fungi were able to grow for a few days, we rated our leaves on how infected they had become.

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As you can see, some grew more than others, but almost all of them have growth of some kind.

The next part of our necrotrophic pathogen lab, was infecting plants with Erwinia carotovora. Since it is a bacteria, we followed the same procedure we used when we infected plants with Pseudomonas syringae, just with the plant genotypes pad2 and Col-0. Since Erwinia is a necrotroph, we were not able to culture the bacteria in the way we had with the biotrophic Pseudomonas, because the bacteria had turned the infected leaves to mush.

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