Well…none other than Zinfandel. I have, of course, followed Tribidrag from the very start.
Tom
As posted on CaroleMeredith’s FaceBook page:
My Croatian research colleagues have long suspected that the old Croatian grape variety Tribidrag was the same as Crljenak kastelanski, which is the modern Croatian name for Zinfandel. They have now confirmed this by purifying and analyzing DNA from an old herbarium specimen of Tribidrag and comparing it to Zinfandel. The DNA profiles are a perfect match. Tribidrag is documented to have been grown in Croatia for at least 500 years.
I want to post the Tribidrag photo here too, but I’m waiting to hear back from the Croatian colleague who sent it to me, just in case he doesn’t want me splashing it all over the intertubes.
Carole
Based on your FaceBook page photo, I gather the Tribidrag sample was taken from a dried out/old/framed leaf
in some old museum??? You can extract a DNA sig from something like that?? How about dried-out/old seeds they’ve
found in some amphora??
Tom
Yes, the Tribidrag DNA was extracted from the leaves of an herbarium specimen in the Natural History Museum in Split, Croatia. Herbarium specimens are representative examples of a particular plant that have been pressed and dried. They are quite dead. Dried leaf tissue can be a great source of high quality DNA. When my lab was analyzing grape varieties from other countries, we couldn’t use fresh samples because the USDA plant quarantine regulations prohibit the importation of living grapevine tissue unless it goes through a quarantine station for disease testing. That takes 2 years! So we figured out how to chemically dry leaf samples using anhydrous calcium chloride. This was quite legal since the leaf tissue was no longer living. But the DNA was very well preserved.
As far as getting DNA out of old seeds, that’s a bigger challenge. First, in most cases the old seeds would not have dried rapidly, so the DNA would be degraded and useless. In a few situations, researchers have been able to extract some DNA from grape seeds but the DNA is usually of low quality and not informative. Second, bear in mind that a grape seed contains the DNA of both the mother plant and the plant that was the source of the pollen. So the DNA profile of the seed would not be the same as the DNA profile of the vine that bore the fruit.
This is all kinds of awesomeness!
I’ve seen DNA sequence pulled from herbarium specimens nearly 100 years old, and heard of limited success with much older samples too! The biggest problem in older material is whether the collector treated the plant with preservatives to inhibit mold/insect damage, which greatly complicates nucleic acid recovery.