2018 ASHS Annual Conference

Brassica, lettuce, and herbal crops are the most commonly grown microgreens due to their simple cultivation, quick germination and short production cycles. Microgreens are increasing popular among consumers, and are especially suitable for greenhouse and controlled environment production. Specialty leafy vegetable crops can be excellent sources of carotenoid phytonutrients, which possess reported health benefits of reducing cancers, cardiovascular disease, and aging eye diseases when regularly consumed in the diet. The objective of this study was to screen fifteen commercially available microgreen cultivars across several greenhouse production seasons for accumulation of nutritionally important carotenoid pigments. 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. Dates and average growing conditions for greenhouse grown microgreen cultivars were: winter (Jan.-Feb.; DLI, 14 mols·d^-1; air temperature, 20 °C); spring (Mar.-April; DLI, 32 mols·d^-1; air temperature, 22 °C); summer (May-July; DLI, 40 mols·d^-1; air temperature, 25 °C); and fall (Aug.-Sept.; DLI, 36 mols·d^-1; air temperature, 27 °C). Shoot tissues were harvested after cultivars reached the first to second leaf stage. Samples were frozen at -80 °C, freeze-dried, and measured for concentrations of b-carotene, lutein, and zeaxanthin pigments using HPLC. Data were analyzed using mixed model in SAS. b-carotene, lutein, and the total concentration of carotenoids pigments within the brassica and lettuce species were influenced by season (P≤0.001), cultivar (P≤0.001), and the interaction of season by cultivar (P≤0.001). b-carotene, lutein, and the total concentration of carotenoids pigments within the herb species were influenced by season (P≤0.001) and the interaction of season by cultivar (P≤0.001). Carotenoid pigment concentrations were higher during the summer and fall seasons when DLI and air temperatures were higher for the brassica, lettuce and herb microgreens and lowest in the winter and spring seasons when average DLI and air temperatures were lowest. With the increasing popularity of microgreens, information on the impacts of cultivar selection and growing conditions on nutritional values would be useful information for producers serving local food systems.