Tomato was domesticated from the wild plant Solanum pimpinellifolium, which grows in equatorial countries including Ecuador and Peru. In these countries, the number of sunlight hours in a day remains relatively constant throughout the year, so the plant cannot use the relative lengths of day and night to detect the changing seasons.
Researchers in Germany found that the circadian clock in the domestic tomato runs on a cycle which is around two hours longer than that of its wild relative. Detailed analysis showed that this longer cycle is driven by a regulatory gene. Experiments which replace this longer-cycle gene in the domestic tomato with the shorter-cycle copy from its wild relative show that plants carrying the longer-cycle gene are shorter, flower later, and have more chlorophyll. All of these changes may in turn improve crop performance.