In a development that could revolutionize agriculture worldwide, scientists working at CIMMYT have taken a crucial step toward creating a high-yielding maize that farmers can plant year after year without having to buy new seed.
After five years of studying more than 50,000 plants, the researchers have finally found two that closely resemble maize but reproduce asexually. This asexual reproduction, known as “apomixis” will someday allow farmers in developing countries to keep their seed pure, unaffected by pollen that often contaminates their seed with unwanted traits. The new plants were derived from crosses between maize and the wild grass, Tripsacum.
The scientists, who are from the French National Research Institute for Development Cooperation (ORSTOM), have been working at CIMMYT since 1991. They first cross-bred maize with Tripsacum, then mated thousands of the descendants with maize repeatedly over several generations. This allowed them to weed out many undesirable characteristics of the wild grass, but still retain the gene for apomixis in plants that began to look more and more like maize.
In the fourth generation of this process, though, the ORSTOM-CIMMYT team "hit the wall," and for almost two years were unable to find any apomictic plants. "We nearly gave up," says Yves Savidan, head of the ORSTOM team at CIMMYT. "I began to believe the task to be truly impossible. But now we have broken through this barrier, and are only a few steps away from developing apomictic maize."
Savidan says that apomixis will allow poor farmers worldwide to boost their harvests at no extra cost. "One lot of high yielding, apomictic maize seed could be planted, harvested, and re-sown indefinitely," Savidan explains. And yields would always stay the same, just as occurs with self-pollinating crops like wheat."
Each “normal” maize plant produces millions of tiny pollen grains. On a favorable wind the pollen can travel kilometers - fertilizing plants far afield. Seed purity and high yields are sacrificed in this scattering.
Maize farmers in industrialized countries can afford to buy fresh, pure seed each crop, keeping harvests plentiful. But in developing countries, commercial seed is either too costly for most farmers or just not available. These farmers are forced to recycle old seed and suffer poor yields.
Because apomictic seed reproduces asexually and includes no genetic contribution from pollen, they nearly always result in a plant that is identical to the mother plant, with no diluting of its outstanding qualities.
Savidan and his team are combining conventional breeding techniques with DNA markers and other advanced science to speed the development of apomictic maize. Once obtained, this maize will be used by breeders worldwide to generate a range of improved varieties and hybrids for farmers.
"We are now planning studies on how farmers can best use apomixis," says Savidan. "Because the trait essentially puts evolution on 'pause', with potential consequences for genetic diversity, its uses will require careful consideration.” But as Savidan also points out, the effects of apomictic maize on cropping diversity may be no more serious than those of other improved maize varieties, and that apomixis could even be used by farmers to conserve favorite local varieties.
"In any case," he says, " we must make the farming more sustainable for the rural poor of Asia, Africa, and Latin America because their options are few, and they have nowhere else to go.
(CIMMYT news release)
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