FEEDING THE HUNGRY SCIENCE LOOKS TO HYBRIDS TO MEET DEMANDS FOR FOOD

Press, Volume CXV, Issue 33741, 14 January 1975, Page 12

FEEDING THE HUNGRY SCIENCE LOOKS TO HYBRIDS TO MEET DEMANDS FOR FOOD

(By

BOYCE RERSBERGER

in the “New 1 brk Times. )

(Reprinted by arrangement)

The political rhetoric, and the good intentions, of the Aiorld Focri Conference in Rome not withstanding, feeding the world’s hungry reman, 'in the longer range, the job of small poor farmers. Helping them meet t rising demand for food is a cadre of agricultural scientists, working • scores of projects to grow new varieties of crops and meat anima, • designed to upgrade the quantity and quality, of food raised in the developing countries.

The centre of activity is nine internationally financed and staffed institutes, in the Philippines, Mexico, Nigeria, Colombia, India, Peru, Kenya, Ethiopia and Taiwan. At the institutes, 200 senior scientists and thousands of technicians are searching for desirable nutritional and agronomical traits in different varieties of food plants and combining them with useful traits from others to breed hybrids that combine the best’of each.

The strategy is based on sophisticated genetics, but the labour involved is drudgery. From start to finish a new crop variety commonly takes four to 10 years of crossing and recrossing before the hybrid strain consistently carries most of the good traits and the fewest of the bad.

Suppose, for example, the goal is to get a wheat plant to change its priorities and channel its growth into big heads of grain on short stalks, instead of smaller heads on nutritionally less useful long stalks. The first step would be to find two wheat types, one short, or dwarf, and the other with good grain and resistant to disease.

Wheat is self-pollenating, or bisexual. A cross is not possible unless the male organs — the pollen-produc-ing anthers — are removed from the flower of the variety chosen to be the female while the plant is still immature.

Emasculating the flower takes tweezers, good eyes and a few minutes for each head. To prevent fertilisation from stray pollen while the female parts mature, a small sack has to be clipped over each flower. Days or weeks later, technicians bring normal flower heads cut from the variety selected to be the male parent. The paper sacks are cut open and the male flower head is thrust in and twirled to create a cloud of pollen within the sack.

In a large plant-breeding programme, tens of thousands, sometimes hundreds of thousands. of such crosses will be made each year. When the hybrid wheat is ripe, it is harvested by hand and saved for planting. Only when the seeds have sprouted and grown to maturity in. the following season will the results be known. Wheat varieties If the goal is shortness, a simple look at the experimental field will show which plants inherited the desired trait. Scientists might choose to plant their seeds directly, and crossbreed again; or to cross the new generation with one of the parents to reinforce the trait still further.

A decade ago, dwarf varieties of wheat and rice that

were also highly responsive to fertiliser resulted from precisely this kind of work. They began what came to be called the Green Revolution, a success in two ways. First, it has been estimated that land planted to Green Revolution wheat and rice now feeds at least 120 million more people than it fed with traditional varieties; second, its imperfections have pointed to new areas for research. In recent years, resistance to several diseases has been bred into many types of rice, wheat, corn, sorghum, barley, potatoes and other crops; work is under way to add resistance to other blights. An additional benefit of such plants is that they minimise the need for pesticides.

An important area of current experiment is in breeding plants that can be grown productively under a wide range of climatic conditions. Drought resistance, tolerance to extremes of temperature, and insensitivity to day length are all desirable traits.

Breeding plants with more nutritive, particularly higher protein, value is another major research area. High protein varieties have been identified in many major crops, including com, sorghum, barley, oats, cowpeas and even potatoes. Scientists are now working to transfer these traits to agronomically viable hybrids. The search for plants with desirable traits is carried on in two ways. One is to sort through “seed banks,” in which samples of seed from thousands of the known varieties of a species are stored. The largest corn bank, in Mexico, holds 12,000 varieties; the chief wheat bank, in Washington, D.C., about 23,000 varieties. Crossing species

The other is to seek in the wild for varieties not known to scientific agriculture. Ethiopia, for example has many now wild varieties of cereal grains from which Neolithic peoyles domesticated crops 10,000 years ago; in 1973 scientists found a wild sorghum in Ethiopia that has 50 per cent more protein than the varieties grown in the United States. If potentially useful genes cannot be found within a given crop, there may still be a source in another species. Until recently, attempts to cross different species of plants have met with little success; now it has been found that anti-re-jection drugs used in animal and human organ transplants can overcome the resistance of, say, a female wheat flower to the pollen from a rye plant. “Wide crosses” usually result, as in the mating of horse and donkey to yield a mule, in sterile progeny. To be fertile, offspring must carry a set of matched pairs of chromosomes, half of each pair contributed by one parent. When different species are crossed, the chromosomes do not all match up. Scientists have found that treating the offspring of a wide cross with a certain chemical, colchicine, doubles all the chromosomes, creating the matched pairs necessary for fertility.

One wide cross has already yielded a new species called triticale. from Trit - cum, the technical name fowheat, and Secale, for rye. Triticale combines the hig) food quality of wheat wit' the disease resistance and moderate drought resistanc, of rye. It was; developed r. Mexico and is planned to be tested in semi-arid Ethiopia For the future, more rad cal crossing is being consid ered. The combination miglr be a cereal and an entireiv different kind of plant, such as a soybean. With the heip of parasitic bacteria, by a process still not fully understood, soybean roots can produce their own nitrogen fertiliser. The technology is not yet here, but some scientists envision a wheat or rice crop that needs no fertiliser. Work on grasses Agricultural scientist.; are also working on the grasses upon which cattle and other animals graze. Large areas of unused grassland in South America and Africa could become rangeland for beef cattle if more nutritious grasses grew there more abundantly. But it is also necessary to breed cattle that can thrive in the semi-arid climate or the high altitude of some of those ranges. Such work is under way, as is research on pigs and poultry with higher protein yield that would be more suitable for smaller farms. The principles of animal breeding are similar to those of plant breeding. The techniques are those used in commercial beef production today: artificial insemination is the most common.

But the possible number of crosses and the time needed to get results make animal breeding a much slower proposition. Cattle breeders, for example, seldom make more than a few dozen crosses at a time, and must wait for years for a herd. In the United States, breeders have come up with a fertile cross between the cow and the buffalo, called a beefalo. There are only 10,000 so far, but the breed shows commercial promise for some of the now idle rangeland in America. The breadth of research on farming in the poor countries might seem to suggest an optimistic future for a now hungry world. But the scientists at the major research centres are among the most tempered of the experts in their expectations. They have been struggling for years, for decades in some cases, to persuade resistant farmers and sluggish governments to develop their own agriculture. As Dr Norman E. Borlaug of the International Maize and Wheat Improvement Centre in Mexico, and a research pioneer, puts it: ‘The varieties we’re turning out now are as far ahead of the first ones we developed as they were ahead of the traditional varieties. Now,Awe still haven’t got all »the farmers growing them the way we’d like but we’re working on that, too.” Now that the North American granaries are no longer bulging, many experts believe there will be more incentive to adopt the new technology.