Greenhouse experiment
One season later (Nov 2013 – May 2014), we raised these 320 genotypes under conditions as above, yet under five water levels. One pot (10 × 10 × 10 cm) per genotype was included in each water level (1600 pots in total). Per pot, 15 seeds of one genotype were sown in a 1:1 mixture of nutrient-poor potting soil and sand, enriched with 0.1 g Osmocote® slow release fertilizer (14-14-14 NPK; Scotts GmbH, Germany). On the first and third day of the experiment, all pots were watered equally to saturation to ensure seed germination. After germination was completed, seedlings were randomly thinned to one per pot and five watering levels were initiated (90 ml, 50 ml, 30 ml, 20 ml, and 15 ml per pot and watering event, respectively). Watering was applied manually with dispensers approx. every 2-3 days, i.e. when most plants in the lowest water level showed strong signs of drought stress. Pots were randomized across the greenhouse and re-randomized every three weeks.