Publications /  Annual Report 1998

Two decades of CIP’s collaboration with China have led to major benefits to Chinese agriculture, and to insights that will benefit the world’s poor.

Sweetpotato vines are an important source of fodder for dairy cows.

"Good food does not just come from grain," notes CIP rural development specialist Dai Peters. "To meet the food demands of the future, alternative crops must be exploited." No country in the world has done more to exploit the potential in sweetpotato than China. For 1995–1997, China’s sweetpotato harvest topped 117 million tons a year, some 85 percent of the world’s harvest. And at 48 million tons, China’s potato crop is second to none; with the break up of the Soviet Union, it is now the world’s largest potato producer.

Between 2000 and 2020, the world’s population will increase by 1.5 billion; half of that growth will take place in Asia. China will account for over 20 percent of Asia’s population growth. For China to maintain its self-sufficiency in food production, potato and sweetpotato crops are destined to play a key role. China produces no yams, and less than 4 million tons of cassava. With this in mind, CIP and China have forged a partnership whose research results can be applied across Asia.

CIP’s collaboration with China goes back two decades. In 1978, the Chinese Academy of Agricultural Sciences sent a scientific delegation to CIP; in turn, a CIP delegation visited major potato-growing regions in China. Regular visits by senior scientists followed. In 1985, the Chinese Academy and CIP signed an accord to set up a regional CIP office in Beijing. Subsequently, with the addition of the sweetpotato to CIP’s mandate, cooperation intensified via germplasm exchange, joint research projects, workshops, and training.

Success with Sweetpotato
Sichuan and Shandong Provinces each produce about 17 million tons of sweetpotatoes a year; together, they account for almost 40 percent of China’s production. In Sichuan, postharvest technology, especially starch production, is a major priority. Since 1978, township enterprises have invested in food processing. In the meantime, dietary preferences in a more urbanized China have shifted. Direct consumption of fresh roots, for example, has dropped. Nonetheless, sweetpotato output has held steady, bolstered by demand from the starch industry. Most of Sichuan’s starch is sold as wet cakes for noodle production. Because starch that is off-white and filled with ash impurities makes an unattractive product, disgruntled urban consumers turn to more expensive, wheat-based pastas. The result is an increased demand for wheat products that China is hard-pressed to meet. Farmers also use sweetpotato as feed, particularly for pigs. As either starch or feed, sweetpotato substitutes for more expensive grains.

Dried sweetpotato slices.

For the past decade, CIP and the Sichuan Academy of Agricultural Sciences have worked on improving starch quality. Manual processing has given way to small-scale mechanized equipment, such as root washers, grinders, raspers, and drum separators. CIP and its Sichuan collaborators identified the variables in extraction, such as the mesh size used for separation, that had the greatest impact on quality. A white, pure starch fetches a higher price and improves, in turn, the quality of products down the line. Transparent noodles are a case in point.

With backing from CIP, the Sichuan Academy developed a motor-driven screw extruder into which the hot sweetpotato dough is pressed. The result is a uniform, high-quality product with better market appeal, a product with just the right viscosity, opaqueness, and thickness. In Santai County, the demand for sweetpotato processing equipment has more than doubled. In 1996, for example, sales of locally made root-washers, starch separators, and extruders totaled over $180,000. In the meantime, of the 91,000 tons of sweetpotatoes that Santai County produced, the proportion processed increased from 36 percent to 76 percent, or to some 69,000 tons. The residues were recycled into animal feed. Santai County now raises 110,000 pigs, a 70 percent increase over 1989.

In Shandong Province, Chinese scientists use tissue culture propagation and ELISA tests to eliminate viruses from sweetpotato planting stock. The project dates back to 1987, when CIP conducted a small course on virus detection. A tissue culture workshop followed the next year. Held at the Sweetpotato Research Center of the Xuzhou Institute of Agricultural Science in Shandong Province, CIP and the Asian Vegetable Research and Development Center (AVRDC) co-sponsored the course. The adaptive research providing the basis for an innovative seed propagation program was carried out by the Sweetpotato Program of the Crops Research Institute of the Shandong Academy of Agricultural Sciences. The Sweetpotato Program has been strongly supported by the Provincial Government of Shandong. This support has been critical to the widespread diffusion of clean planting material. Today, the work is sponsored by the Shandong Academy of Agricultural Sciences.

Scientists generate virus-free plantlets from meristem tip culture in order to obtain vine cuttings. Starting with just 500 plantlets the first spring, the project produced enough foundation seed to cover 6.7 hectares in vines by the second spring. In turn, cuttings from these vines generated 100 hectares of roots, or some 3000 tons of seed. By the third spring, the project had enough stock to plant over 13,000 hectares. Thanks to this effort, the province’s farmers began to plant virus-free sweetpotatoes in 1994. The impact on yields was dramatic; the average productivity advantage across nine sites and five varieties was over 40 percent. The added output requires no additional fertilizer, water, or change in farming methods. Almost any farmer who uses virus-free material gets higher yields. In 1998, Shandong farmers planted half a million hectares of virus-free sweetpotatoes, or about 80 percent of the province’s total. An estimated 3.1 million farm families benefited from the added yields, valued at $133 million a year. In Shandong, sweetpotato starch, especially for noodle-making, is a growth industry. Currently, half Shandong’s output goes to the local starch industry.

As a staple food, sweetpotato can be eaten fresh or dried in the sun for subsequent use. Both roots and vines make an excellent animal feed. In many parts of China, however, sweetpotato’s future is linked to its multiple starch transformations: noodles, vermicelli, and sheet jelly; refined starch; starch derivatives (amylophosphate, amylum acetate, and soluble starch); and starch residues (fodder, maltose and sugar residues, brewing products). That being the case, breeding for high dry-matter content, which directly adds to the amount of starch extracted, is a top priority for CIP and Chinese breeders. According to Dapeng Zhang, CIP plant breeder and project leader, the objective is "to produce more usable material in every sweetpotato." The recovery rate for starch averages about 15 percent (by weight) of the unpeeled fresh roots. Sweetpotato varieties with enough dry matter to boost starch recovery by just 5 percent to 20 percent could add an impressive one-third to the total extracted. Varietal selection is done in cooperation with China’s Sweetpotato Research Center in Xuzhou, Jiangsu Province.

Potato has made a difference in people’s diets in China; in two decades, the country's production of this crop has almost doubled.

Not only is China the world’s top sweetpotato producer, but the crop is dispersed across five distinct climatic zones. Sweetpotato is rarely the main crop. China’s farmers plant them in elaborate rotations with grains (rice, wheat, corn, millet), oil seeds, sesame, and assorted legumes (soybeans, peanuts, field peas, broad beans). In some zones, intercropping prevails, with sweetpotatoes on ridges and corn or peanuts planted in the furrows between. Rotations help improve soil structure, control pests, and foster soil fertility. Intercropping maximizes the use of space, distributes labor, and increase a field’s overall productivity. CIP scientists have much to learn from how China’s farmers manage their fields, information vital to Asia’s food production.

Progress with Potato
China today is the largest global user of CIP germplasm. For the potato, germplasm exchange dates back to 1978, the year CIP-24 entered China as an in-vitro plantlet. The Wumeng Agricultural Research Institute in Inner Mongolia did the propagation and field trials. This hardy, drought-tolerant cultivar is currently produced on over 150,000 hectares. CIP germplasm still contributes to varietal development in China. CIP entries are evaluated in multilocational trials across north China at both Wumeng and Yanqing stations. Selection criteria include resistance to late blight and bacterial wilt, plus early maturity and drought tolerance.

Almost 40 percent of China’s potato crop is produced in the north in a one-crop-per-year system. Farmers repeat potatoes or rotate to wheat, oats, or buckwheat. Further south, potato is sown as a fall or winter crop that follows wheat or paddy rice. To be profitable, farmers need early maturing varieties. In 1991, CIP’s Philippine-based UPWARD network (Users’ Perspective with Agricultural Research and Development) began a potato production project for the rice-based cropping systems of Zhejiang Province. The principal researcher was Zhang Rentian of the Zhejiang Academy of Agricultural Sciences. So far, the project has introduced technology that shortens the potato’s growing season; it has also moved seed multiplication to the highlands, where disease pressure is less, and it has organized more than 350 training sessions for 18,000 farmers. A potato rotation improves subsequent rice yields. Combining the two crops, food production per unit of land area has more than doubled.

In China’s southern provinces, intercropping potatoes with other crops is commonplace. In Sichuan Province, the country’s largest potato producer, 80 percent of the potato crop is intercropped with corn: the potatoes in the furrows, the corn on the ridges. When it comes to rotations and intercropping, China’s potato farmers are the experts.

Partners in Progress
In 1978, when CIP and China began collaboration, the country’s total potato harvest was estimated at 25 million tons. Two decades later, China’s production has almost doubled. For sweetpotato, which was added to CIP’s mandate in 1985, total production first fell in the 1980s and has been steadily rising since the early 1990s. What changed the most was the sweetpotato’s utilization. On a fresh-weight basis, sweetpotato is China’s second most important crop after rice; the potato is ranked fifth. To bolster its food production, China needs its potato and sweetpotato crops. Working together, China and CIP have much to learn, and much to offer each other.