|CERES No. 074 (FAO Ceres, 1980, 50 p.)|
research in Peru
Interest in the potato has been increasing steadily in the developing world. Because of its high food value, it is generally considered an improvement in quality over the many tuber crops already grown in these regions.
Yet the potato is basically a temperate crop (around 85 percent of the world's production occurs in the north temperate zone), and one relatively unadapted to high temperatures and humidity. Tropical conditions aggravate the plant's already high susceptibility to diseases, due largely to the fact that it is usually propagated vegetatively, permitting the transmission of many pathogens from generation to generation. In addition, the product is perishable and subject to many storage diseases.
Most importantly, it is almost impossible under tropical conditions to eliminate the potato's worst enemy: aphids, small plant-sucking files, which transmit viruses from plant to plant and from farm to farm. Even crop treatment with pesticides will usually kill aphids only after they have infested the plant. Besides viruses, several species of bacteria and fungi also cause potato diseases. Yields are drastically cut and quality sometimes suffers if the tuber sections used for sowing, known as seed potatoes, come from diseased plants.
As a result, most tropical countries must import the egg-sized seed potatoes to plant crops. The cost of seed potatoes usually represents an astonishing 50 to 60 percent of total production costs in tropical zones. Transportation costs are high, and the tuber cuttings require refrigerated shipment and storage and constant sanitary attention to avoid rotting and disease. Furthermore, developing countries sometimes receive varieties that are conditioned to the countries where they originated, causing adaptation problems.
Responding to these and other problems, the International Potato Centre (CIP), headquartered in Lima, Peru, is carrying out research aimed at replacing seed potatoes with botanical seeds, the true seeds of the potato fruit ball, usually employed only for breeding. CIP claims the use of botanical seeds could convert the potato into a food staple- instead of a luxury-for low-income sectors in tropical zones of the world. "The benefits would be fantastic," says FAO Agricultural Officer C. Rosell. "It would have a tremendous impact on the potato industry."
Botanical seeds would account for only 5 percent of total potato production costs in tropical zones. Transportation costs are obviously much lower, and seeds can be stored safely for months inside glass bottles. CIP says the amount of seeds needed to sow 1 hectare of potatoes would fit into the palm of a hand, whereas 2 tons of seed potatoes would be needed to plant the same area. Furthermore, the ability of seeds to resist disease is substantially greater than that of seed potatoes.
Although even in ancient times botanical seeds were used to achieve new varieties, usually potato fruits were thrown away because only the roots were considered usable. In the late nineteenth century, the American breeder Luther Burbank produced the large, smooth variety of potato named in his honour by using botanical seeds. About 25 years ago, research was undertaken to use these true seeds for sowing purposes. Unfortunately, the same genetic variability that Burbank depended on has been the main obstacle in replacing seed potatoes with botanical seeds.
Since seed potatoes are essentially clones, offspring receive the same genetic blueprint as the parent. Instead, planting true seeds, the results of the genetic reshuffling that always accompanies regular sexual reproduction, ensures tubers with a wide range of characteristics.
"It is still not well known how to obtain an homogeneous variety of potato by using true seed," affirms Rosell. "And of course stabilizing a variety is a must of any seed production programme; consumers in the tropics as well as in the developed world look for specific potato types with a certain appearance and Havour."
Still, CIP claims that variations among certain botanical seed examples have recently been reduced to acceptable levels. As a result of the Centre's research, there have been successful harvests in four different areas of Peru: the coastal, highland and low-land tropics, and the tropics located 1000 metres above sea level. In addition, an experimental station in North Carolina in the United States produced its first potato harvest from botanical seeds in 1977.
But the greatest success with botanical seeds has been realized in the People's Republic of China. Traditionally, the Chinese have had to transport tuber cuttings from northern Mongolia to tropical regions in the south, incurring high transportation and storage costs. Currently, China is producing botanical seeds in Mongolia for shipment south; the country transported 2.5 million tons of true seed in 1977 with excellent results.
CIP has seven centres operating as technology transfer units: three in Asia, two in Latin America and one each in Africa and Turkey. Their work includes maintaining contact with national research and extension institutions to disseminate the Centre's scientific discoveries and to detect local adaptation problems. The Centre hopes that the new species produced from botanical seeds will take hundreds of different names all over the world, and that this multiplication of names will serve as a yardstick for their success.