Advertisement
News

Farmers are lowering plant gene pool by sowing only Green Revolution hybrids

The farmers of the world, harvesting the abundant crops of the Green Revolution, have so far defied Malthusian predictions that population growth would outrun agricultural production and consign much of humanity to chronic famine.

But scientists say the diverse varieties of traditional crops and wild plants they need to breed more productive new strains are in jeopardy.

Advertisement

In the field, farmers are abandoning them in favor of the new high-yield varieties.

Wild strains of agricultural plants are disappearing as development destroys their habitat. And lack of funds, lack of care, and political upheaval threaten the collections of seeds, in "banks" around the world, in which much of the remaining genetic diversity is stored.

Advertisement

The prospect of losing this genetic capital would be alarming under any conditions, scientists agree, but it is particularly threatening because of the way Green Revolution crops have changed the world's agriculture.

In the first phase of the revolution, high-yield strains of wheat and rice bred especially to accommodate and thrive on large amounts of synthetic fertilizer enabled harvest yields to double and triple in much of the Third World.

Famine caused by underproduction has largely disappeared; hunger today is mostly a product of political upheaval, bad administration of food supplies or the inability of the poor to buy food.

But this historic achievement has exacted a price: while the new crops are vastly more productive than traditional varieties, they are also much more vulnerable to catastrophic destruction by insects, fungi, bacteria and viruses.

Genetically uniform crop strains have been adopted across wide stretches of the earth. As a result, pests or diseases that used to be local problems can race across nations and continents, cutting a destructive swath through the world's food production.

To counter this threat, plant breeders must continually add new resistance traits to crops by crossing them with traditional and wild varieties.

The same genetic techniques also allow scientists to confer on crops characteristics that contribute to higher yields -- tolerance to drought, heat or cold, for instance. And they offer a benign alternative to synthetic pesticides and fertilizers and the environmental harm these can cause.

Some of the most recent results have been dramatic:

Advertisement

* Scientists at Cornell University under contract to the International Potato Center in Lima, Peru, combined a nonedible wild potato from the Peruvian Andes with a conventional edible potato. Their offspring inherited a highly desirable characteristic from the wild plant: tiny hairs on the leaves and stem that entrap insect pests. The hairs exude a substance that adheres to the insect's feet, immobilizing it. The trait also prevents egg-laying and feeding and makes the plant highly resistant to all major potato pests, eliminating the need for pesticides. The pests cause major crop losses annually, and eliminating them would boost productivity. Cornell plans to test the potato in New York State fields this year.

* In another advance, scientists at the International Maize and Wheat Improvement Center in Mexico City are breeding wheat resistant to the Russian wheat aphid, an insect that costs the United States $300 million a year in lost production and %o insecticides. The scientists are crossing the modern wheat with traditional agricultural forms found in Turkey. Five more years' worth of breeding cycles should achieve resistance, scientists say.

* Researchers at the International Center for Tropical Agriculture at Cali, Colombia, have identified wild bean plants containing antibiotics that keep bruchid bean weevils from reproducing. The weevils infest stored grains and destroy up to 15 percent of the total bean harvest of Latin America and 25 percent of the harvest in Africa. Insecticides cannot be used because they would poison the beans. The wild beans have been crossed with cultivated beans and are now being field-tested in Latin America and Africa.

The advances were described, and alarms about the loss of genetic diversity were sounded last week by scientists at a symposium in Washington sponsored by the Washington-based Consultative Group on International Agricultural Research.

This is a broadly based consortium that supports a worldwide network of research centers and gene banks in the forefront of the enterprise.

A similar warning was sounded earlier this month in Oslo, where an international group representing research organizations, foundations, governments and seed producers resolved to launch a global initiative aimed at heading off the danger.

Advertisement

If the erosion and deterioration of genetic resources continues, the group said in a statement of consensus, "genetic options for needed changes in agricultural production in the future will be lost forever."

The group advocates a five-fold increase, to $300 million a year, in financing for the preservation and development of genetic resources.

The Green Revolution itself is one contributor to the threat. As farmers increasingly adopt the new high-yield strains of rice and wheat, they abandon their traditional varieties. Traditional varieties of crops, scientists say, are the richest source of diverse genes. Unless the traditional varieties are collected and preserved as they are abandoned, their genes are lost. Wild strains are disappearing as development destroys ecosystems.

Collecting plants in the field is arduous and time-consuming, and there are few collectors with the necessary expertise. There are perhaps 15 of them in the Americas, Dr. H. Garrison Wilkes, a biologist at the University of Massachusetts at Boston, told the Washington meeting.

Nearly half a million agricultural plant samples now repose in international gene banks, and more reside in national collections. But many scientists agree that the condition of some of the collections is deteriorating.

Many samples have been in storage for a quarter of a century and must be regenerated by planting. Many seeds are probably already dead, scientists say, victims of inadequate manpower and money.

Advertisement

Some gene banks, the Washington conferees were told, are becoming "gene morgues."

Other gene collections are useless, researchers say, because their contents have not been identified, analyzed and cataloged, leaving them, in effect, like a library without a card catalog -- or even any book titles.

Political strife threatens some collections, as in Ethiopia. At the Oslo meeting, said Dr. Don Plucknett, scientific adviser to the Washington-based research consortium, the Ethiopian representative "was really sweating every day" because of the potential threat that unrest in his country posed to the gene bank there. In Bolivia a few years ago, protesting workers at a gene bank ate the national collection of potato seeds.

They were replaced from international stocks, but not all national stocks are duplicated elsewhere.

All of this is especially unsettling, many scientists believe, given United Nations' forecasts that the world's population will grow by nearly a billion people by the end of this decade.

World agriculture is not ready for that, Dr. Wilkes said. "We're losing our diversity" in genetic resources "and we don't have our gene banks in the best operating order," he said.


Advertisement