Evaluation of several lettuce varieties based on economically valuable traits and nutritional value under vertical hydroponic cultivation conditions

Background: The cultivation areas of Lettuce (Lactuca sativa L.) are increasing daily in both open and protected ground conditions. It is stable in the population's diet because it contains vitamins C, B1, B2, PP, P, E, K, folate, and carotene. The leaves are rich in over 30 mineral elements, such as nitrogen, potassium, calcium, iron, magnesium, and phosphorus. The chemical composition of lettuce varies depending on the cultivation conditions. In vertical hydroponic greenhouses, lettuce is cultivated year-round, providing eight to nine harvests. Introducing varieties rich in bioactive substances for an economically valuable production is crucial. Objective: The research aims to evaluate the content of bioactive components such as ascorbic acid and vitamin A, macro and microelements, and productivity in local and imported lettuce varieties grown hydroponically, focusing on enhancing food functionality. Method: The research objects are the Cencibel RZ, Levistro RZ, Manushak, and Veradarc varieties of lettuce (Lactuca sativa). Experiments were set with 3 repetitions. The spectrophotometer (Carry 60 UV-Vis, Agilent Technologies, USA) was used to identify the content of ascorbic acid and vitamin A. The refractometric method determined the dry matter content, and the total sugars were measured according to Bertrand's method. The composition of elements N, K, Ca, Mg, and Fe was determined in lettuce at the Organic Agriculture Laboratory of Armenian National Agrarian University with a photometric LASA-AGRO 3900&1900 workstation․ The total yield and marketability yield of the variants studied were recorded using the weighing method. Results: Different varieties' growth and development phases varied between five to eight days. The Manushak variety was found to have biometric indicators, forming lusher, curled green leaves, and larger leaf rosettes. The Manushak variety excelled in yield per unit area (m²), providing 4.8 kg/m², surpassing other varieties by 1.3-1.1 kg. The highest amounts of vitamin A and C were recorded in the Manushak variety (0.35 mg and 15.1 mg, respectively). The Manushak and Cencibel RZ varieties showed high indicators of macro and microelements. For example, the amount of Vitamin K was 205.5 mg in the Manushak variety and 205.0 mg in the Cencibel RZ variety. Conclusion: Comparative studies of local and imported lettuce varieties led to the following conclusions: the local variety "Manushak" excelled in vertical hydroponic conditions, demonstrating superior early growth, better morphology, higher yield, and enhanced nutritional value. Keywords: lettuce, variety, vertical hydroponic, yield, phenology, chemical composition, nutritional value