Wildfong, Bob, Alternatives Journal
Farmers and gardeners are the best hope for protecting what remains of food plant diversity
THE ABILITY TO ACQUIRE viable, well-adapted seeds has allowed human beings to form civilizations, set up permanent settlements and build cities, supported by a reliable and bountiful source of food.
Throughout history, hundreds of species of plants have diverged from their wild roots. It is their ability to adapt and change that has made plants so important to us. Without controlled breeding and selection, it would be impossible to grow acres of corn as far north as Canada, wheat would be no more than a wild grass, and all apples would be tiny crabapples.
Many times, we have had to change the kinds of food crops that we grow. As people moved to different areas of the world and developed different farming technologies -- from simple ploughs to giant combines -- their seeds changed with them.
We have inherited thousands of varieties of useful plants that exist only because farmers and gardeners have grown them, produced seeds, and grown them again. Hardly any of these domesticated plants could live without human care. Our plants are a chain of seed-saving, but that chain is breaking.
The natural and human history of our food system is at the roots of issues affecting crop diversity in modern times. In the 1920s and 30s, the Russian biologist and explorer N.I. Vavilov studied the genetic distribution of cultivated plants throughout the world and discovered that their greatest natural diversity occurred in several tropical and subtropical regions. He concluded that crop plants had originated in these regions, which he called "gene centres", later to be known as "centres of diversity". 
Agriculture is considered to have begun independently in three areas of the world, where edible grains grew in the wild: wheat, barley and millet in North Africa, beans and corn in Central and South America, rice in east Asia. Early hunter-gatherers discovered that these grains could be planted intentionally, putting an end to the nomadic need to travel to find more food. 
When the earliest farmers began cultivating foodgrain crops, seeds were part of their harvest. The kernels of wheat and millet that they ate were also used to plant their next crop. Seed saving was a natural act of setting aside a portion of the harvest to be sown at planting time. In contrast to our modern practice of buying seeds as an input, early farmers used seeds as part of a self-renewing cycle.
Until recently, farmers in the centres of diversity have had an enormous selection of wild plants to include in their seed stocks. Wild relatives of crop plants that displayed drought tolerance, insect resistance, or other favourable qualities would be brought into cultivation to eventually give those strengths to the cultivated crop. Since each farmer could propagate a slightly different set of varieties, or a different ensemble of plant genes, a staggering number of useful plant varieties evolved on the simple farms of Africa, Latin America and Asia.
The collections of seeds grown by traditional farmers are often called "landraces" or "farmers' varieties".  These are mixed, highly diverse populations. In a field of traditional African landrace wheat, the plants are genetically heterogeneous. Many slightly different plants grow side by side, creating a form of crop insurance. If dry weather suits certain plants, then those plants thrive. If the weather turns cold and wet, others grow better. Either way, there is usually an adequate harvest, and rarely a total crop failure.
Traditional farmers trade seeds with one another, always searching for those that grow best on their particular patch of land. The best grains are saved for planting and only the second-grade seeds are used for food. High-land farmers and low-land farmers often have different types of plants, fields on sand and fields on clay support different types, all developed through natural and human selection. …