Evaluation location: Pennsylvania, United States
Plants were grown in a completely randomized design in a greenhouse located on the campus of The Pennsylvania State University in University Park, PA (40°48′ N, 77°51′ W), from May through July 2009. Three biological replications were grown per accession, and replications were planted 7 d apart in the same greenhouse. Before planting, landrace seeds were soaked for 1 h in a mixture of benomyl (methyl [1-[(butylamino)carbonyl]-1H-benzimidazol-2-yl]carbamate) (Benlate fungicide, E.I. DuPont and Company, Wilmington, DE) and 1.3 M metalaxyl (2-[(2,6-dimethylphenyl)-(2-methoxy-1-oxoethyl) amino]propanoic acid methyl ester) (Allegiance fungicide, Bayer CropScience, Monheim am Rhein, Germany). Following the fungicide treatment, five seeds per accession were germinated for 48 h in darkness at 28°C in rolled germination paper (Anchor Paper Company, St. Paul, MN) moistened with 0.5 mM CaSO4, 8 mM benomyl, and 1.3 M metalaxyl. Teosinte seed was scarified with sandpaper and soaked in 0.5 mM CaSO4 for 48 h before germination. For each accession, one seedling with a 6 to 8 cm primary root was selected for each replication. The seed of each seedling was planted at a 4 cm depth although mesocotyl length varied among accessions and individuals. Plants were grown in 10.5 L pots (21 by 40.6 cm, top diameter × height, Nursery Supplies Inc., Chambersburg, PA). The growth medium was composed of 45% peat, 45% vermiculite, and 10% silica sand, limed to pH 6.0. The nutrient solution consisted of the following: 2211 μM NO3, 777 μM NH4, 398 μM CH4N2O, 411 μM P), 1858 μM K, 1455 μM Ca, 960 μM Mg, 16 μM B, 0.33 μM Cu, 7 μM Zn, 8 μM Mn, 0.85 μM Mo, and 16 μM Fe ethylenediaminetetraacetic acid. Following seedling establishment, 2 to 3 L of nutrient solution were applied as needed to each pot three to four times per week via drip irrigation using a DI-16 Dosatron fertilizer injector (Dosatron International Inc, Dallas, TX). Irrigation volume and frequency increased as plant development proceeded. Sulfuric acid was injected into the water supply to acidify the irrigation water to a pH of 6.0. Environmental data were collected hourly in the greenhouse using a HOBO U10-003 datalogger (Onset Corporation, Pocasset, MA). Mean ambient temperature was 26.5°C ± 5.9 (day) and 21.3°C ± 2.4 (night), and mean relative humidity level was 57% ± 12.2. Maximum photosynthetic flux density was 1200 μmol photons m−2 s−1.