by Elizabeth de Páez, CIAT
Scientists are hot on the trail of an "apomixis gene" that lets plants reproduce vegetatively, but through seeds rather than plant parts such as stolons. Breeding that gene into crops means that farmers may someday plant seed from their own harvests of high-yielding hybrids, year after year, without buying new seed, says John Miles, geneticist at the International Center for Tropical Agriculture (CIAT).
"That could transform agriculture in both developing and industrialized countries," Miles says. "It could give farmers in developing countries access to the same types of hybrid seed that modernized agriculture in industrialized countries."
Commercial production of hybrid seed is expensive because it requires the controlled crossing of parents for each crop, Miles explains. First-generation hybrids are usually more vigorous than the parents, but that vigor is lost in later generations. Seeds harvested from a hybrid crop cannot be re-sown: their yields are too low and variable.
"But if we breed an apomixis gene into a hybrid, and it expresses itself, the seeds would exactly reproduce the vigor and other useful traits such as disease-resistance," says Joe Tohmé, CIAT plant geneticist. "The problem is to find that gene. It's a bit like looking for a needle in a haystack."
CIAT scientists have identified in a brachiaria grass "molecular markers" that will help them find this gene. "That means we've limited our search to a small part of the haystack," Tohmé says.
Once found, the next step is to clone the gene into unrelated crops such as rice, which feeds 2.5 billion people. The markers confirm that a single dominant gene controls apomixis in brachiaria. Cloning may take three to five years. "But then we will be able to develop true breeding hybrids that could yield 30 percent more than current varieties," Tohmé says.
Except for citrus, apomixis is rare in crops of economic importance, Miles says. Most apomixtic genes are found in wild relatives of crops. "But the wild plants are so different that scientists have had little success in transferring their genes into domesticated crops through conventional breeding."
(CIAT News Release)