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COLUMN ONE : In Search of Genetic Diversity : Nature's storehouse of genes has been exploited for many advances in agriculture and medicine. Is the storehouse being depleted?


"We keep demanding the very best available (and that will) have a tendency over time to narrow the genetic bank," Dr. Major M. Goodman, a statistical geneticist at North Carolina State University, said.

That was the case in the fields of America's Corn Belt in 1970, when the best farmers in the world had planted the very best available seed on prime land, using plentiful water, the latest equipment and techniques.

The best seeds were hybrid varieties--yielding more than 80 bushels of corn per acre, four times the average of just 40 years before. And, they were vulnerable: The very genetic qualities that made the corn seed so desirable also made the corn susceptible to a fungus, called Southern Corn Leaf Blight.

In 1970, the blight wiped out about 15% of the U.S. corn harvest, costing American farmers more than $1 billion. The farmers, livestock ranchers and consumers around the world who rely on U.S. corn harvests were lucky. A turn in the weather stopped the leaf blight before it got to the rest of the crop.

It could have been devastating, because so few varieties, only a dozen or so, accounted for 80% to 90% of all the corn planted in the Corn Belt. The scare was enough to rivet national and worldwide attention on the dangers of genetic uniformity.

After the corn leaf blight, a study by the National Academy of Sciences reported that many major food crops were "impressively uniform genetically and impressively vulnerable." The problem was not just in corn, but in vital crops such as hard red winter wheat, soybeans and potatoes.

The shock waves from the corn blight registered throughout the international agricultural community. A new agency to support worldwide collection and preservation of agricultural diversity was formed in 1974 by the internationally supported Consultative Group on International Agricultural Research.

The Consultative Group's worldwide network of research centers is primarily devoted to plant breeding; ironically, its work in introducing new high-yielding, disease-resistant crops to agriculture-poor nations in the 1960s and 1970s that sparked the phenomenal increases in food production, called the "Green Revolution," has also been criticized by some genetic conservationists as having contributed to loss of genetic diversity.

Most plant breeding and research around the world is concentrated on a few dozen species of crops--out of the thousands and thousands of food crops raised and eaten around the world--that are of major economic significance. In many cases, the research is further specialized because the aim is to develop higher-yielding varieties of these crops. This results in collecting practices and policies that focus on the genetic materials of the most modern, already highly bred or cultivated varieties, called cultivars.

For plant genetic information, it is the equivalent of having a "world history" library that had books about only a handful of countries, and then, only those volumes that had been written in the last few decades.

So, like many collections, the research center seed banks are not safes of genetic diversity, but reflections of their more pragmatic goals, said Dr. Calvin O. Qualset, director of California's Genetic Resources Conservation Program.

Neglected at these banks are seeds of lesser known crops, that while less globally significant still may be very important to a particular region or culture. Also under-represented at seed banks are the primitive varieties, wild relatives and land races of the major crops, whose genetic properties are less understood or more difficult to use in breeding programs. Land races are varieties cultivated and bred through traditional techniques by peasant farmers, often over hundreds of thousands of years.

Third World development projects and increased environmental woes--reaching further and further into the native habitats of such crops--have put at highest risk the very crops that are least represented in seed banks. The countries poorest in commercial agriculture, whose people may subsist on a few local crops that aren't protected in major collections, remain the most vulnerable to irretrievable crop losses.

In the meantime, more and more farmers around the world are planting new and often hybrid crop varieties--a trend helped along by a consolidated and globalized seed industry. Instead of the old ways of saving seeds from the best of one year's crop for planting the next, peasant farmers now must buy seeds for each planting.

When they turned to modern farming techniques and new hybrid varieties, Third World farmers often abandoned their historical food crops. In many countries, this process was often encouraged by foreign and local government aid policies that subsidize farming only if the farmers plant the new varieties.

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