Putting nutrients back into wheat
Breeding can repair a poor mutation in cultivated crops.
When ancient farmers first domesticated wheat some 10,000 years ago, they were trying to breed a crop perfectly suited to making food. But it seems that somewhere along the line, farmers unwittingly took out a gene that packs the plant full of goodness. Now researchers have found a way to fix that old mistake and put the nutrients back.
A team led by Jorge Dubcovsky of the University of California, Davis, looked at more than 90 varieties of the two major types of wheat (Triticum turgidum) that are today cultivated for making pasta and bread foodstuffs that account for around 20% of all calories consumed worldwide. In all of these strains, the researchers found a mutation that reduces the amount of protein, zinc and iron in the grain.
The researchers have successfully crossed wild and crop strains to create a new variety with increased micronutrient levels and 10% more protein than traditional farm strains. The discovery could help many of the estimated 2 billion people with deficiencies in key micronutrients. "We're releasing a variety that will be on the market next year," says Dubcovsky. "We've tested the quality and it makes very good bread."
The gene speeds up the process of 'senescence', in which the plant's leaves die off and nutrients are remobilized to the developing grains. The mutated version in traditional cultivated strains results in fewer nutrients making it into the grains by the time the crop is harvested, the researchers explain.
They tracked down the gene responsible by using a map of genetic markers showing which areas of the genome are associated with different traits. Having identified the region associated with higher nutrient levels, they analysed the genetic sequence to find the crucial genes.
To test their theory, Dubcovsky's team used a gene-silencing technique called RNA interference to shut down all genes related to NAM-B1 in crop strains, and found that the nutritional content of the grains declined even further. Their results are reported in Science1.
The new strain is "not a magic bullet", Dubcovsky stresses. "You will still have to test it in your own environment." He and his colleagues are set to release their variety onto the US market, but if other regions were to follow suit, wild strains would need to be crossed with local crop varieties to ensure that the result is suited to growing in local conditions. Other factors, including soil quality, can also influence the health value of plants (see ' Taking the acrylamide out of wheat').
But the development is open to all. Dubcovsky says "anyone who asks for it, we will give them the seeds". The university has a patent on the gene, but the plants are in the public domain.
Some 80% of US wheat varieties are public; it is a self-pollinating species, so farmers tend to develop their own strains without needing to buy proprietary versions. As a result there has been little commercial motivation to make a better wheat plant agricultural companies have traditionally focused on other crops.
Dubcovsky has now set up an effort called the Wheat Coordinated Agricultural Project to allow others, particularly in the developing world, to learn how to breed nutritious wheat strains for themselves, although he stresses that the process has taken his lab 10 years from start to finish.
More than 160 million children across the world lack adequate protein, which is vital for growth and development. How much the new research will help the developing world, however, depends on whether the resources can be found to mount similar breeding campaigns there, Dubcovsky says. "The problem of malnutrition is more a problem of distribution," he points out. "But if somebody wants to do it, all the information is available."
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- Uauy C., Distelfeld A., Fahima T., Blechl A., Dubcovsky J., . Science, 314 . 1298 - 1301 (2006).