(image via wikimedia commons)
Have you ever wondered about the genetics of dinner at an Italian restaurant? Probably not. Chances are, though, that the species of wheat in your garlic bread was different than the one used to make your spaghetti.
Humans have a complicated relationship with wheat. We've been cultivating many species for thousands of years and have molded these species' characteristics using selective breeding. Many wheat species are polyploid, meaning that they have more than two sets of chromosomes (that's how many humans and most animals have), which generally makes genetic manipulation difficult. However, Monstanto, the largest producer of genetically modified crops, is developing genetically modified wheat, although it won't be on the market for several years.
Some people have a severe intolerance to wheat gluten, a protein found in wheat, called Celiac disease. People with this disease have a severe immune reaction to wheat gluten that damages the intestinal lining, causing a host of symptoms. Related proteins found in rye and barley will likely also cause these symptoms. Since all species of wheat are related and produce similar proteins, Celiac sufferers must avoid all species of wheat in their diets. Currently, there is no cure for Celiac disease, although it can be managed with diet. The exact mechanism is still under investigation.
In case you've ever wondered, here is the 411 on some common species of wheat that you will encounter at your grocery store or neighborhood restaurant:
1) Common wheat or Bread wheat (T. aestivum) is a hexaploid species that is the most commonly cultivated in the world.
2) Durum wheat (T. durum) is a hard wheat used to make semolina flour for pasta.
3) Spelt (T. spelta) is a wheat species that is recently gaining in popularity but still less prevalent than other types.
4) Emmer wheat (T. dicoccum), also known as Farro, was widely cultivated in ancient times but is less prevalent now. It was specifically referred to in several ancient texts.
5) Einkorn wheat (T. monococcum) is a rarer type of wheat that may be less toxic to Celiac sufferers1
Additionally, there are many, many other species of wheat that I don't have the space (or frankly the willpower) to go into here. Interested parties are referred to this excellent Wikipedia article.
Wheat is usually ground into flour, using all (in the case of whole wheat) or part (in the case of white) of the wheat kernel. In general, "hard" wheats contain more protein, which makes dough made from their flour more chewy and elastic. They are best for bread and pasta, whereas "soft" wheats contain less protein and are best for cakes, biscuits, etc. "All-Purpose" flour is usually a mix of these two types and can be used for a wide variety of purposes, hence the name.
1Pizzuti D, Buda A, D'Odorico A, D'Incà R, Chiarelli S, Curioni A, Martines D (November 2006). "Lack of intestinal mucosal toxicity of Triticum monococcum in celiac disease patients". Scand. J. Gastroenterol. 41 (11): 1305–11.