| The quiet revolutionaries a look at the campaign by agricultural scientists to fight hunger |
Spreading these new varieties to African countries outside Nigeria is more difficult Cutting can carrypathogens such as viruses, bacteria, and fungi that trier disease and pests, such as insects and mites.
These make quarantine officers nervous. It is believed that cassava bacterial blight (as well as the infamous mealybug) reached Africa and Asia from tropical America on infected cuttings.
Returning to the United States, airline passengers have to declare whether they are carrying any plants or food or admit if they have been on a farm or ranch while overseas. On both my trips to Colombia and Nigeria, after tramping aver numerous
I admitted to the latter. On neither occasion did the immigration officers in Miami and Washington bother to check up. The task is too immense, even for the most conscientious team of officers.
Millions of passengers stream through international airports every year, and can without realizing it, carry a pest or pathogen in their baggage or on their bodies. Sometimes passengers purposely carry through plant materials, and they go undetected Then there's first-class mail which is unopened And an cargo flights and military flights, often unscheduled or flying at short notice, that slip by quarantine officers. Millions of tons of grain are shipped every year—it's an impossible task to cheek every container.
Even when the quarantine officers know that a quantity of new material is waiting for their inspection-they have the power to deny it entry or destroy it—the task remains daunting. Nearly 1,600 different pests and pathogens are on the target list worldwide. Some pathogens are difficult to detect, some have yet to be identified, and some infected seeds show no signs of infection. It's not surprising that quarantine services are swamped and that crop breeders, anxious to spread their new varieties into another country, get annoyed by delays and what they consider unscientific or out-of-date decisions.
One answer is to use tissue culture techniques for transporting root and tuber crops such as cassava, sweet potatoes, and yams. Shoot tips are put in a nutrient liquid in a test tube, and they grow into plantlets. These plantlets are not. only diseasefree, but are less bully than cuffings, so it's cheaper to move them around as air freight. More than thirty countries in Africa, for example, have now received improved cassava in this form from IITA in Nigeria.
A Drought in Africa
And spreading new tougher varieties throughout large parts of Africa, the cassava experts believe passionately, must become a top priority bemuse of the appalling drought-the worst in fifty years that has struck much of the eastern and southern parts of the continent Not only is famine threatening some 20 million people, but even if the rains return to normal in 1993, it'll take some years for agriculture to recover fully. Some farmers have been slaughtering their cattle because there has teem no water to give them so putting their future livelihood at risk
Maize is the staple crop of most southern African countries, but maize fails without a lot of water. Scientists have yet to come up with maize varieties that can cope with severe drought But cassava, remember, can grow in poor soil, needs little or no mineral fertilizer, can be left in the ground for up to two or three years until its needed, and demands little water Its roots dig deep into the ground to search for moisture and, in the severest drought conditionals, it sheds its leaves to reduce evaporation.
James Cock, an Englishman who now runs the national sugarcane research center in Colombia, was for eighteen years the cassava program leader at ClAT. In the mid-1980s he wrote the best book available for the layman on cassava. Cassava: New Potential for a Neglected Crop. I asked him whether, if he were to write the book now, or update it, he would change anything.
"I'd pay much more attention to the drought side of it," he replied firmly. "It's just incredibly tolerant of drought. Its a super plant. Its proving its worth in African drought areas. It could move into areas like the Sahel. Its one of the few crops that's still producing in Blazil when they have their periodic droughts. It's the only thing that prevents massive starvation." In the old colonial service in Africa, he said, district officers used to insist that every fanner have a certain amount of cassava as an insurance crop. And, at that time, "Africa didn't have the food problems to the extent it does now. There wasn't the population pressure on the land."
Zimbabwe, one of Africa's great hopes for agricultural success, was badly mauled by the drought and has fumed, among other crisis measures, to cassava ."All their maize is dying," Dixon said. "They're working with us in trying to get cassava production going. Cassava germplasm is being sent to a laboratory at the University of Zimbabwe and their national program will start field bests. What we are thinking now is to make a massive injection of cassava germplasm to Zimbabwe, at the request of the Zimbabwean government."
"Will the farmers grow it and will the people eat it?" I asked.
"They are used to it in some areas. It'll depend on the extension workers who'll have to convince the framers of the potential of the crop-that you can use it in various ways."
Cassava need not replace maize in people's diet in Zimbabwe according to Marcio Porto, a Brazilian physiologist He mid a recent conference in Maputo, Mozambique, that cassava could be used to feed animals, fleeing up the maize for human consumption Porto, who works for CIAT but is attached to IITA to introduce new American cassava varieties into Africa, also argued that Brazil's experience with cassava and with drought could help Africa.
Preserving the Germplasm While the scientists push forward with their experiments to feed the hungry, they are faced with another crisis: the germplasm that they need to create new varieties from old is become more and more scarce. Ironically, the green revolution speeded up the loss of genetic diversify. In the past, farmers naturally selected (often on advice from their fathers and grandfathers), seeds or cuttings that proved to be good-crops that fought off those pests and diseases and put plenty of food on their tables (or on the floors of their caves and huts). There were thousands of different strains of a crop, each with its own hereditary material carrying genetic information passed along from one generation to the next—how it tastes, what color it is, how it fights back against drought This is called germplasm, and in concrete terms this means simply seeds, bulbs, roots, and tuber cuttings. These traditional varieties are known as landraces and they are at risk of disappearing.
The miracle crops of the green revolution tend to be genetically uniform, and that can lead to disaster. If you have grown millions of acres of genetically identical potatoes or corn and they are struck by a disease, the whole crop may be destroyed. That's what happened in the Irish potato famine in the 1840s when a fungus caused famine, death, and mass emigration. That's what happened in 1970 when a corn leaf blight struck from Florida to Texas, causing a loss of about a billion dollars. Farmers and scientists, it was realized, need those landraces— those traditional strains-for their genetic diversity, for their possible strengths and as-yet-unknown characteristics.
They are disappearing because of a reliance on the improved varieties, because of the expanding deserts, and because of the spread of "civilization": the cuffing down of trees' the building of dams, the expansion of cities. At the present rate of this kind of "destruction," some 60,000 plant species—nearly a quarter of the world's total-will be lost to the gene pool by the year 2050.
So a crucial and exciting hunt is on. Plant explorers fan out to find and rescue as many strains of landraces (and also their related wild ancestors) as they can, before it's too late. And then hand them over to the safe custody of gene banks to be kept in trust for future generations. Explorers working for IITA, so they boast, have gone to "remote corners of Africa, risking life and limb, contracted tropical diseases far from anything resembling medical care, and, at least once, been sent packing by a hungry pride of lions."
The classic collectors' success story is of a handful of Mexican wild beans, carefully collected twenty years ago in southern Mexico by Dr. Howard S. Gently, an American scientist traveling on muleback The beans eventually landed up in CIAT'S gene bank and were later found to contain arcelin, a novel protein that blocked the digestion of the dreaded Mexican bean weevil, a pest that was busy devouring great quantities of beans in storage. The arcelin gene was bred into commercial varieties, allowing beans to be stored in Latin America and Africa without the use of pesticides.
Scientists take a gene and insert it into another variety, either by traditional cross-pollination—the fertilization of one plant with the pollen of netic engineering. In the latter a gene is removed from one plant with chemicals or other means, and then spliced into another one. These genes have to come from the landraces or their wild relatives; scientists cannot just invent them.
It was a Russian plant geneticist, Nikolai Vavilov, who preached the necessity of research into the origins of cultivated plants and of preserving collections of genetic material He traveled the world from 1916 to 1933 collecting thousands of plant varieties, bringing them back to research stations. He also argued that each basic food plant had its origin in a certain area of the world; that area was where a plant had the most genetic diversity. Maize is found in the greatest diversity in Central America—there is its center of origin. For potatoes it's the Andes. And for cassava it's the northern part of South America.
Vavilov's fate was perhaps inevitable, considering Soviet history in the first part of this century. He ran foul of T. D. Lysenko, the all-powerful biologist whose bizarre theories were supported by Stalin and adopted throughout the Soviet Union. Vavilov was arrested in 1940 and died of starvation in prison in 1943. The World Bank is trying to raise money to help preserve Vavilov's priceless collection of plant genetic material in St. Petersburg.