Two independent experiments were conducted in this study. Experiment 1 was done with a mapping population of 360 accessions (33), and Experiment 2 used a set of 473 accessions. Each accession in each experiment had four replicates under each of the four growth conditions (two planting seasons by two locations).
Both experiments were conducted in two walk-in growth chambers (AR-916, Percival Scientific) that were programmed to cycle the local climates every 5 min from the simulated weather files. The simulated climates were generated by using SolarCalc (35) with sunrise and sunset, light spectrum, temperature, and relative humidity programmed to cycle throughout the day and the season according to 1975?2000 averages (Fig. S5). One chamber was simulating Spain (latitude 41.72091, longitude 2.957075) starting from March 1, and the other chamber was simulating Sweden (latitude 55.71226, longitude 13.207352) starting from May 1st on the first day when plants were put into the chambers.