Georgofili World

Newsletter of the Georgofili Academy

Ancient DNA

DNA records the biological characteristics of organisms that have adapted to the environment in which they live. Today DNA can also be extracted from ancient organisms, with analyses of its structure offering the possibility to evaluate the evolutionary distance covered when compared with contemporary DNA. Despite all this, there are difficulties because, thus far, the ancient DNA is almost always degraded and, in some cases, in a fragmentary state, just like an encyclopedia in which most of the letters on the thousands of pages that have reached us are erased or faded. Plants differentiate from other living beings both because of the thick walls and polysaccharide teguments that protect the nuclear DNA and because of the plastids, characteristic organelles that are also protected by two unit membranes. Moreover, nuclear DNA degrades exponentially and to a greater extent than plastid DNA. The entirety of plastid DNA passes from the maternal parent to the offspring and is a powerful tool for tracing matrilineal lines back, an original Eve who lived in a specific historical time and place. These phylogeographical surveys are essential for understanding the routes of plants useful to humans and are therefore anthropic as they were selected, domesticated, and transported. Thus, alien species spread to different geographical areas where they then adapted and reproduced and, in some cases, transformed agriculture, thereby modifying the area’s biodiversity. Our past is full of such episodes. The Etruscans and Romans introduced allochthonous varieties in their habitats. Beginning in the mid-17th century, the Islamic conquests abolished alcoholic products and pork. Later, with the discovery of the New World, beans, potatoes, peppers and chilies, tomatoes, marrows, and maize were introduced. As in the past, we are witnessing the same phenomenon today, in which the interbreeding of new plant and animal species can cause radical changes that may supplant or attack autochthonous species. To fight this natural entropy and to preserve typical varieties (e.g., in viticulture), starting in 1850 with the import of powdery mildew, downy mildew, and phylloxera from the New World, wine-growers have suffered great losses. For the survival of ancient local varieties and of the prized wines typical of a natural viticulture, a suitable rootstock had to be found together with effective treatments both in the vineyard and in the cellar. What would happen if the millenary viticulture of our ancestors were to be re-established with fields of legumes and cereals spaced out by rows of ungrafted Trebbiano, Malvasia, Gorgottesco, Colorino or Sangiovese supported by stakes or maples? In the Department of Life Sciences in Siena, we are trying to develop surveys on the genetic historicity of ancient anthropic cultivars. Apart from today’s discussion of whether a product is natural, organic, biodynamic, or treated, it will be fascinating to have the possibility to decipher the DNA of an ancient organism perhaps to compare it with an alien or a para-autocthonous organism that has adapted to a certain distributional area. Knowing when an anthropic plant species was introduced into a habitat generally means discovering who brought it, tracing its evolution and derivative products back, and identifying its taste – a voyage into the past that can be better understood and for ever longer periods. Surely, knowing what has happened in the past may be very useful to planning the future.