The findings were published in a journal, The Plant Cell.
Kent Bradford, director of the university’s Seed Biotechnology Center, said researchers targeted problems heat poses for growers during fall plantings in California’s Imperial Valley, and Yuma, Ariz.
Depending on how breeding proceeds, the find could result in reduced need for sprinkler irrigation, seed priming and other treatments to enable hot-weather germination.
“It’s not an earth-shattering discovery, but it’s something that should over time as it gets incorporated into more germplasms make things a little easier,” Bradford said. “Particularly if we think that global warming is happening and temperatures will go up everywhere. It may be more important than we think.”
The study focused on a gene that determines production of abscisic acid, a plant hormone that inhibits seed germination. That gene is switched on in most lettuce seeds when exposed to moisture at warm temperatures, increasing acid production. In a wild ancestor of commercial varieties, the gene does not turn on. So the acid is not produced and seeds can still germinate, researchers found.
Commercial application would not require genetic modification, according to Bradford.
“These are natural sources of high temperature tolerance that can be bred into lettuce,” he said. “Breeders can use molecular markers to move that in. We also have mutants in the gene that knock it out or reduce its activity, and those too would not require any genetic engineering.”
Plant scientists have been crossing the wild ancestor mostly into the Salinas variety of iceberg developed by the U.S. Department of Agriculture.
“We’re still about six or eight months away from having what we hope will be a Salinas with very little of the wild germplasm in it,” Bradford said. “By later this year we think we’ll have good material. It would be up to companies to incorporate this iceberg type into other types as needed.”
The new paper builds on earlier publications.
“There are likely some breeding companies starting to incorporate this material, but most probably not yet,” Bradford said.
His coauthors include scientists from Arcadia Biosciences, Davis, Calif.; and Acharya N.G. Ranga Agricultural University, India. Related research has been done by lettuce geneticist Richard Michelmore and Cal Poly Pomona plant science professor David Still.