The discovery could lead to year-round lettuce production, according to a news release.
The study included researchers from the University of California, Davis, Arcadia Biosciences and Archarya N.G. Ranga Agricultural University in India.
The researchers say because the same mechanism is found in many other plant species, their work could lead to better germination as global temperatures increase.
Most lettuce varieties bloom in spring or early summer, then drop their seeds.
Because lettuce originated in the Mediterranean region, the built-in dormancy mechanism prevents seeds from germinating during the hot, dry summers.
To circumvent the trait, growers cool the soil with sprinkler irrigation or prime seeds to germinate by pre-soaking them at cool temperatures, then re-drying them before planting.
The practice can be expensive and isn't always successful.
The researchers, led by UC Davis plant sciences professor Kent Bradford, identified a region of chromosome that enables a wild lettuce species to germinate during the heat.
When that region was crossed into commercial lettuce varieties, they also gained the ability to germinate during warm temperatures.
Further genetic mapping zeroed in on the specific gene in commercial lettuce responsible for shutting germination during warm temperatures.
The scientists then demonstrated they could either silence or mutate the gene in cultivated varieties, enabling them to germinate and grow even during high temperatures.