|Simon: Garlic Origins|
The origins and distribution of garlic: How many garlics are there?
Philipp W. Simon, USDA, ARS, Vegetable Crops Research Unit, Department of Horticulture, University of Wisconsin, Madison, WI 53706
Garlic in History
Garlic is among the oldest known horticultural crops. In the Old World, Egyptian and Indian cultures referred to garlic 5000 years ago and there is clear historical evidence for its use by the Babylonians 4500 years ago and by the Chinese 2000 years ago. Some writings suggest that garlic was grown in China as far back as 4000 years ago.
Garlic grows wild only in Central Asia (centered in Kyrgyzstan, Tajikistan, Turkmenistan, and Uzbekistan) today. Earlier in history garlic grew wild over a much larger region and, in fact, wild garlic may have occurred in an area from China to India to Egypt to the Ukraine.
This region where garlic has grown in the wild is referred to as its "center of origin" since this is the geographic region where the crop originated and the only place where it flourished in the wild. In fact, although we sometimes hear about "wild garlic" elsewhere in the world, this is the only region where true garlic routinely grows in the wild without the assistance of human propagation. There are other plants locally referred to as "wild garlic", but these are invariably other species of the garlic genus (Allium), not garlic itself (Allium sativum). For example, Allium vineale is a wild relative of garlic that occurs in North America and is commonly called "wild garlic".
The "center of origin" for a plant or animal species is also referred to as its "center of diversity" since it is here that the broadest range of genetic variation can be expected. That is why those of us who have sought to find new genetic variation in garlic have collected wild garlic in Central Asia.
Once cultivated by the first garlic farmers outside of its "center of origin", what types of garlic did early afficianados grow? In fact, we know almost nothing about the early types of garlic produced. No designation of garlic varieties was made in the early writings discovered to date, be it hardneck or softneck, red or white, early or late, local or exotic. Throughout its earlier history some have speculated that softneck garlic was the predominant type cultivated although evidence of what would be interpreted as a hardneck type was found interred in Egyptian tombs. It was not until garlic was cultivated in southern Europe within the last 1000 years that the distinction between hardneck and softneck was routinely noted. Until more ancient writings which describe garlic are found, or old, well-preserved samples are unearthed, we can only speculate about the early types of garlic grown.
Garlic producers and consumers have come through 5000 years of history growing and eating their crop with little need to specify type or variety. In fact it is a rather modern habit of only the last few hundred years whereby more detailed descriptions of varieties have come to be developed for any crop plant.
Garlic Migration, Propagation, and Reproduction
Throughout history, humans migrating and travelling through Central Asia and surrounding areas have collected wild garlic (and still do) and carried it with them for later consumption and cultivation. In 1989 I was fortunate enough to participate in a germplasm collection expedition seeking garlic and other alliums in nature reserves of Central Asia. We observed primarily hardneck garlic in the wild, but some softneck plants also occurred. It is easy to imagine early garlic connoiseurs migrating beyond the natural range of wild garlic and carrying wild garlic far from its center of origin. Only with cultivation could a supply for subsequent years be assured. And so garlic came to be cultivated.
The wild hardneck garlic we collected is among the more prolific for production of true garlic seeds. We presume that the vast diversity that has been observed in cultivated garlic goes back to variation generated from sexual reproduction in the wild crop. In contrast to wild garlic, as far as we know, garlic in cultivation throughout history has only been propagated asexually by way of vegetative cloves, bulbs, and bulbils (or topsets), not from seed. These asexually propagated, genetically distinct selections of garlic we cultivate are more generally called "clones". Unlike sexually reproduced crops propagated from seed, vegetative reproduction assures a very uniform crop.
Yet this asexual lifestyle of cultivated garlic forgoes the possibility of combining traits profferred by interpollinating diverse parental stocks. Let's say you have two garlic clones, clone A and clone B. Clone A has excellent yield but poor storage ability while clone B stores well but yields poorly. Without an opportunity for interpollination and sexual reproduction, the only way to obtain a garlic clone with high yield and long storage is to wait for the desired mutations(s) to occur in clone A or clone B. If these two clones can, however, be interpollinated and set true seed, a very realistic opportunity exists to develop a new line with both desired traits in several generations of progeny selection beyond this cross. Sexual reproduction and selection are at the heart of plant breeding in agriculture and, for that matter, evolution in wild plants.
No sexual reproduction, that is, production of true garlic seed, was underway in cultivated garlic before the 1980's. Therefore, relatively small numbers of garlic clones, perhaps numbering only a few thousand, have been in the hands of growers around the world through most of history. We conjecture that these clones represent the cumulative array of garlic diversity resulting from sexual reproduction in the wild which has been disseminated from its center of origin throughout history and then been able to successfully produce a crop in the hands of garlic growers around the world today. Superimposed upon the variation resulting from sexual reproduction of garlic in the wild, we can also expect to find variation due to mutations that accumulated throughout the history of cultivation of the crop.
Garlic is crop widely grown for fresh market by many producers on a small scale for local markets and, particularly in the U.S., by a few large-scale producers for processing and fresh sales. About one million hectares (2.5 million acres) of garlic produce about 10 million metric tons of garlic globally each year, according to the United Nations Food and Agriculture Organization.
Although widely cultivated, it is only since routine seed production became possible in the 1980's that garlic can be called a domesticated crop, since a strict definition of domestication is the process of selective breeding of a plant or animal to better meet human needs. Clones held by growers today have been maintained as separate entities, but a system to confirm or refute the identity of a given clone has not been established. Only with several seasons of careful field observation can garlic clones be identified, and even then ambiguities often remain. For example, virus infection can dramatically reduce plant size and vigor, and alter leaf color and shape making unequivocal garlic identification impossible.
Why Fingerprint Garlic Clones?
Fingerprinting was developed to prove, or disprove, the identity of humans. Today the term "fingerprinting" is used more widely to include evaluation of DNA patterns of any organism. High-profile criminal/legal proceedings have made the concept of fingerprinting (in its broader sense) familiar to the general public in that context. The very same DNA methodologies useful for humans are applicable for any organism.
What can be learned from garlic fingerprinting? Three situations arise where it would be useful to have an unequivocal means to verify the identity of a garlic clone: identification of existing garlic clones in production, tracking of new garlic clones derived from true seed as they enter and move into production, and development of a garlic lineage.
For garlic, there is a good likelihood in any large collection that several garlic clones held under different names that, in fact, are identical. Another scenario we often confront is that several clones occur as a mixture under the same name. This brings us to the first motivation for fingerprinting garlic. The possibility that perhaps only a few thosand garlic clones were collected in Central Asia and found their way into cultivation outside of that region with a vegetative method of propagation, makes the prospects for an opportunity to fingerprint most of the garlic cultivated today a realistic proposal.
Furthermore, with true garlic seed being produced on a large scale today, many new clones will certainly enter the production stream for the first time in history. With this, the need for varietal identification becomes more urgent. A DNA fingerprinting effort of garlic today will serve as a useful foundation for tracking new clones coming to growers in the future.
A third rationale for DNA fingerprinting of garlic is more subtle. This methodology not only tells us that clone A is different from clone B and clone C, but it also can tell us how closely related clones A, B, and C are relative to each other. In this way DNA fingerprints provide modern insights into historical events for which no other historical record is available. Comparative analysis of DNA fingerprints have provided important insights about the origins and movement of human populations, cultivation and domestication histories of crops and farm animals, and sources of disease organisms.
Garlic is a compelling and well-appreciated, but little-studied crop. It has a long history in the hands of humans and a significant monetary, health, and social value in modern society. A better understanding of garlic origins and distribution may help us better understand not only garlic, but perhaps our own human history.