Rapid Progress in Winter Wheat Breeding Has Large
Impact
Thanks to an innovative program based in Turkey, the impact of research to develop better winter wheat varieties for developing countries has risen dramatically in recent years.
The Penalties of Harsh Winters
and Short Growing Seasons
Some of the world’s most disadvantaged people live in relatively inaccessible areas in Central and West Asia and North Africa (CWANA), where winter and facultative wheats supply food and income for the household (see box below). Rainfall for growing crops is scarce—less than 350 mm per year—and grain yields are low, frequently less than 1.3 tons per hectare. Winters are long and cold. The short growing season provides few or no options for producing multiple crops, so wheat-fallow rotations are still widely practiced. The hilly, stony landscape makes it difficult as well as costly to mechanize or irrigate. Infrastructure is poor in winter wheat areas, which are the least developed in the region. People have limited contact with anyone who can provide new seed or information.
Yet wheat is the paramount crop for these people, and their need for new seed and information is acute. Compared to spring wheat, the investment in breeding improved winter wheat varieties in developing countries has been much smaller and occurred more recently. Not surprisingly, average yields of rainfed winter wheat in these countries (1.3 tons per hectare) have grown less rapidly than yields of spring wheats (averaging 2.5 tons per hectare). Winter wheats bred in other parts of the world are often of little use in CWANA because they succumb to yellow rust disease. The few resistant varieties usually need a longer growing season to reach maturity, or they cannot tolerate other local stresses such as drought or zinc-deficient soil.
Rapid Development of
New Varieties
For many years, CIMMYT worked with partners in temperate countries to cross winter and spring wheats, with the goal of improving partners’ winter wheats and CIMMYT’s spring wheats. Over time, the scope of CIMMYT’s research widened to include improving winter wheats for developing countries. In 1971, CIMMYT began working directly with Turkey’s winter wheat improvement program through an association with the Rockefeller Foundation—A government of Turkey wheat research program. In 1990, Turkey’s Ministry of Agriculture, CIMMYT, and ICARDA initiated joint research on winter wheats through the Turkey—CIMMYT—ICARDA International Winter Wheat Improvement Program (IWWIP).
Turkey generously provides access to its research institutes and other infrastructure, enabling Turkish, CIMMYT, and ICARDA scientists to distribute new winter wheats to more than 120 breeding programs in 50 countries. This international network for breeding winter wheat is among the world’s largest. Though much of the research is done in Turkey, complementary research—for example, molecular fingerprinting or breeding for insect resistance—is done elsewhere by CIMMYT and ICARDA.
Winter wheat breeders, like farmers, have only one growing season per year to do their work. It takes 12-15 years to breed a new variety and get it into farmers’ fields. To date, 30 varieties developed by IWWIP have been released and 34 others are scheduled for release.
Given that IWWIP started just 17 years ago, this number
is impressive. Progress has been good partly
because researchers crossed winter wheats with spring wheats developed
by CIMMYT in Mexico, which has resulted in the development of both superior
winter and spring wheats. More than 75% of the IWWIP wheats that have
been released or are scheduled for release are crosses between winter
and spring wheats and some of the most successful spring wheats have winter
wheats in their parentage.
Benefits Spill Over
into Afghanistan
Another impact of IWWIP has been its steady collaboration with Afghanistan over the years. Governments rarely view agriculture as a priority in times of civil disorder, but despite war with the USSR and the upheavals of subsequent years, Afghanistan’s wheat researchers stuck to their jobs. Through the Swedish Committee for Afghanistan and FAO, Afghan researchers maintained contact with IWWIP and selected the best new wheats from the international nurseries. Much of Afghanistan’s infrastructure was destroyed, but new wheat seed still moved from farmer to farmer. Without this seed, the Afghan people would have suffered even more hunger and malnutrition over the years. All winter and facultative wheat cultivars currently registered in Afghanistan are derived from these nurseries and several Afghan wheats have been registered in Turkey.
Farmers in Central and West Asia and North Africa contend with cold winters, scarce rainfall, and a short cropping season for the wheat that is their chief staple.  Blowing in the wind: movement of a virulent strain of yellow rust. |
Overcoming
Diseases, Pests, and
Other Stresses
In this region of the world, where wheat was domesticated, many pests and diseases evolved along with the wheat crop. The wide spectrum of pest and disease problems is often aggravated by the unpredictable and variable climatic conditions and other stresses. The development of disease- and pest-resistant wheat varieties is a key strategic component in improving food security across CWANA. The best sources of disease resistance for a particular area cannot be identified without a good understanding of the epidemiology of the diseases that prevail across CWANA’s wide range of agro-ecologies. Pathologists from national and international organizations throughout the region regularly survey farmers’ crops for diseases and pests. They pay close attention to how the pathogens causing these diseases are evolving. One of researchers’ major achievements has been to identify the “hot spots”—not only in CWANA, but worldwide—where the pathogens that cause different diseases evolve most rapidly and provide the key to developing new, resistant varieties.
Wheat now covers a wide swathe from Iran to Mongolia, leaving no natural barriers to rust spores traveling on the wind from other regions. Most commercial wheat varieties in Central Asia are highly susceptible to yellow rust. In the last decade, Central Asian farmers suffered wheat losses as high as 50% in two major yellow rust epidemics. With resistant varieties from IWWIP, the risk of yellow rust epidemics is diminishing. Central Asian breeding programs have used IWWIP varieties to fortify their own varieties since the mid-1990s.
Spring, Winter, and Facultative Wheat: What’s the Difference? A wheat variety’s growth habit limits its survival to certain geographical areas. Knowing the distinctions between winter, spring, facultative, fallsown, and spring-sown wheat can make the difference between crop failure and a bumper crop. Spring wheats die if exposed to temperatures below –10°C
for more than 12 hours. Winter and facultative wheats, however,
need exposure to cold (2-10°C) for three to six weeks after
they germinate, or they cannot produce grain. They start to grow
before winter sets in, when they become inactive. Vernalization—a
temperature response mechanism—ensures that winter wheat and
other plants adapted to cold climates do not enter their reproductive
growth stages prior to winter. The plants resume rapid growth in
the spring as temperatures rise. Spring-habit wheats have a continuous
growth cycle with no inactive period. Facultative-habit wheats tolerate
cold more than spring wheats and less than winter wheats, To complicate matters further, farmers often call fall-sown wheat cultivars winter wheat, irrespective of whether they are of winter or spring type. Since most wheats in CWANA are sown in fall, confusion over wheat types can have terrible consequences. When seed is imported to help farmers cope after natural disasters or war, for example, a mistake can be catastrophic. Farmers who mistakenly sow winter wheats in springtime or in warm areas will harvest only grass—not grain. The IWWIP partners can inform relief organizations about appropriate wheat seed and prevent mistakes from occurring. Wheat in Central and West Asia and North Africa Of the roughly 100 million hectares planted to wheat in the developing world, about 70% is planted to spring type wheats, which cover about 25 million hectares in CWANA. About 30% is planted to winter and facultative type wheats, 16.4 million hectares of which are in CWANA (Figure 1). All 10 countries with the highest per capita wheat consumption in the world are located in CWANA. More than 90% of the CWANA wheat crop is consumed as food, and wheat often provides more than half the calories in people’s daily diets (Figure 2). It is easy to see why a disease epidemic in the wheat crop, a nutrient deficiency in the grain, or a reduction in grain quality could have ruinous economic and health consequences for many families. Population is growing more rapidly in CWANA than the average for developing countries, and most countries strive to produce as much wheat as they can to meet domestic demand and limit imports. No other region of the world devotes so much land to cereal production. For example, as much as 70% of arable land is planted to wheat in Turkey and Iran.
Figure 1. Locations where varieties
from the Turkey/CIMMYT/ICARDA
|
For more information: h.j.braun@cgiar.org
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January, 2005