No More Parched
Wheat Fields
| Each year, drought strikes more than half of the area sown to wheat in the developing world. If predictions are right, an even larger expanse of land will become parched every year owing to global warming, urbanization, and deforestation. As conditions worsen, farmers will need varieties that tolerate drought and farming practices that promote more efficient water use. |
 Crosses that went into breeding the new, high-yielding, drought-tolerant wheats. |
Thirty Percent More Wheat under Drought
New, hardy bread wheats in the pipeline at CIMMYT have been designed to fit new, tougher circumstances. They are descended from crosses between different types of wheat and goat grass, one of wheat’s wild relatives (see figure). The new wheats have produced up to 30% more grain for two years running in tests comparing them to one of their parents under tough dryland conditions. “I’ve worked in Australia, in a very dry environment, for much of my life, and this is the biggest breakthrough in drought tolerance I’ve ever seen,” says Timothy Reeves, director general of CIMMYT. Drought tolerance genes inherited from their wild ancestor have made all the difference.
The parent they beat is no loser—on the contrary, it is a very high-yielding wheat that grows well in many semiarid environments around the world. It has endowed the new wheats with valuable traits: resistance to several diseases, good grain quality, and, more importantly, the innate capacity to produce high yields with different amounts of moisture. The new wheats switch on their drought tolerance and express this high yielding capacity under conditions that would shrivel most wheats.
How Do the New Wheats Work?
The new wheats are meant for dry locations where producers are changing the way they farm to make better use of water, control soil erosion, and maintain soil fertility. Some farmers have started doing very little or no plowing and leaving the straw of the previous crop on the soil surface (see: "Zero-Tillage: Averting Dry Wells and Depleted Soils in South Asia"). Depending on climate, other farmers may plant their wheat deeper than usual to take advantage of rainwater stored in the soil.
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Seedlings of the new wheats are so vigorous they can force their way up through crop residues and from lower soil depths. This vitality comes from deep roots that anchor them firmly in the ground and from long, strong coleoptiles (developing stems) that push right through the soil and any stubble on the surface (see figure). After the plants emerge, they produce numerous leaves that extend outward horizontally. The leaves quickly cover the ground, shading the soil and conserving moisture.
The new wheats also do well when rain is sufficient to produce a good harvest, as happens occasionally in some dry environments. They take advantage of the added moisture to produce more grain.
The key to getting the new wheats to yield as much as possible is to grow them using the right farming practices. This is facilitated by the new wheats’ versatility, for they can be sown under different planting systems—for example, on flat ground or on raised beds, with and without crop residues on the soil surface, and with little or no plowing. These useful traits will give farmers in marginal environments the flexibility they need to deal creatively with the problem of water scarcity and the growing demand for wheat.
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For more information: Richard Trethowan (r.trethowan@cgiar.org) |
Published on October 2001
August, 2004