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I’ll Rust Your Tissue…

For the past two weeks the Nelson Lab has been filled with rust and tissue. But listen, don’t get this confused with the kind of rust from the bottom of your car or tissue you use to blow your nose!

Tissue collection is a very important aspect of any genetic analysis. It is collected in many different styles and performed for many reasons, as I learned the hard way this past week. Many of the tissue samples I collected from the nursery stock will be used simply to see which plants must be cross pollinated to create the next generation with a desired trait. These we collect into tiny plates, being sure to clean our tweezers off on our cloth between every pluck of sawdust size tissue. I later aided the grad students with the DNA Extractions of this same tissue where we got a quick lesson in SNP’s and SSR’s. SNP’s can be performed much quicker than SSR’s and the information is shown as a cluster in a computer generated graph rather than the tough to analyze peaks of the SSR’s.

Then we had to hole punch one piece of tissue out of each plant in the row to get the row average of specific recombinant inbred lines. These we loaded into Costar tubes, which apparently work well to create a DNA that will, as the grad students say “LAST FOREVER,” which is quite ironic as collecting that tissue TAKES FOREVER!

The last type of tissue collection I will discuss is one that i enjoy the most. No bending over for hours. No hole punching. Just grab some scissors and snip it! This tissue we collected into small envelopes for later use.

After all this tissue collection I was glad to switch to rust duty. I learned that Rust is a biotroph. This means that it needs a live host to grow and sporulate. This is very different from the Northern Corn Leaf Blight cultures I am accustomed to. NLB is a necrotroph meaning it grows on a host and kills it in order to utilize the dead tissue, making it very convenient to culture in a lab on Petri plates.

Since we have a large amount of plants in a trial searching for rust resistance on a specific QTL, we cultured our rust on live plants in the greenhouses here at Cornell. By using this QTL selection method or Quantitative Trait Locus we can essentially practice selection for a number of generations until the desired phenotype for the quantitative trait is identified. Once the rust was spreading on our flats of sweet corn we carefully collected the leaves and rinsed them in water to collect the spores. After a spore count we diluted spores into a liquid inoculum. We then trucked out to the field to inoculate the corn with our usual repeating pipetters.

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