2017 ASHS Annual Conference

Microgreens are increasing in popularity as specialty crops for greenhouses and controlled environments. Brassicas, lettuces, and herbal crops are the most commonly grown microgreens due to their fast germination and production time and simple cultivation needs. Concentrations of water soluble carbohydrates in microgreens will contribute to flavor attributes. The objective of this study was to screen fifteen commercially grown microgreen cultivars in cool, low light and warm, high light environments for germination timing, fresh mass (FM) accumulation, and water soluble carbohydrate concentrations. Five cultivars each of lettuce, herb, and brassica crops were grown under greenhouse conditions using a soilless peat mix in solid-bottom plastic trays (26 x 52 x 3 cm) and misted daily using a fine spray nozzle head. All aboveground microgreen FM was harvested after plantlets reached the first to second true leave stage. Samples were freeze-dried and measured for concentrations of water soluble carbohydrates using HPLC. During production, conditions for the cool, low light environment were (daily mean): PAR, 161 μmols·m^-2·s^-1; DLI, 14 mols·d^-1; air temperature, 20 °C. Growing conditions for the warm, high light environment were (daily mean): PAR, 467 μmols·m^-2·s^-1; DLI, 40 mols·d^-1; air temperature, 25 °C. Data were analyzed using Spearman’s rank order correlation to determine the monotonic relationship of cultivars across the two environmental growing conditions. Rank order correlation for days to germination was r_s=0.771 (P ≤ 0.001). Cultivars averaged 5.8 days to germination in the low light environment and 4.5 days in the high light environment. Rank order correlation for FM was r_s=0.832 (P ≤ 0.001). Fresh mass of cultivars averaged 92.8 g per flat in the low light environment and 97.3 g per flat in the high light environment. Rank order correlation for tissue sucrose (r_s=0.712; P ≤ 0.001), fructose (r_s=0.757; P ≤ 0.001), and glucose (r_s=0.911; P ≤ 0.001) were also significant. Cultivar tissue sucrose averaged 13.8 mg·g^-1 dry mass (DM) in the low light environment and 7.21 mg·g^-1 DM in the high light environment; tissue fructose averaged 13.38 mg·g^-1 DM in the low light environment and 15.36 mg·g^-1 DM in the high light environment; and tissue glucose averaged 14.11 mg·g^-1 DM in the low light environment and 17.31 mg·g^-1 DM in the high light environment. Cultivar rankings for germination timing, FM production, and water soluble sucrose, fructose, and glucose remained stable over different environments. Stability in cultivar ranking for yield and quality may be useful information for microgreen producers.