Citation: Juškeviˇ cien ˙ e, D.; Radzeviˇ cius, A.; Viškelis, P.; Maroˇ ckien ˙ e, N.; Karklelien ˙ e, R. Estimation of Morphological Features and Essential Oil Content of Basils (Ocimum basilicum L.) Grown under Different Conditions. Plants 2022, 11, 1896. https://doi.org/10.3390/ plants11141896 Academic Editors: Giedr ˙ e Samuolien ˙ e, Darius Kviklys, Neringa Rasiukeviciute and Kristina Laužik ˙ e Received: 27 June 2022 Accepted: 19 July 2022 Published: 21 July 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). plants Article Estimation of Morphological Features and Essential Oil Content of Basils (Ocimum basilicum L.) Grown under Different Conditions Danguol˙ e Juškeviˇ cien˙ e 1, * , Audrius Radzeviˇ cius 1 , Pranas Viškelis 2 , Nijol ˙ e Maroˇ ckien˙ e 1 and Rasa Karklelien ˙ e 1 1 Department of Vegetable Breeding and Technology, Lithuanian Research Centre for Agriculture and Forestry, Kauno 30, Kaunas Distr., 54333 Babtai, Lithuania; audrius.radzevicius@lammc.lt (A.R.); nijole.marockiene@lammc.lt (N.M.); rasa.karkleliene@lammc.lt (R.K.) 2 Laboratory of Biochemistry and Technology, Lithuanian Research Centre for Agriculture and Forestry, Kauno 30, Kaunas Distr., 54333 Babtai, Lithuania; pranas.viskelis@lammc.lt * Correspondence: danguole.juskeviciene@lammc.lt Abstract: This study was carried out in the experimental field and in unheated greenhouses of the Lithuanian Research Centre for Agriculture and Forestry Institute of Horticulture. The investigation aimed to evaluate the morphological features, amount of essential oil, and productivity of 10 basil (Ocimum basilicum L.) cultivars grown under different growing conditions. Studied cultivars were different according to morphological parameters, productivity, and the accumulation of essential oil. Most of the investigated parameters were influenced by growing conditions. Basil plants of cultivars Sweet Genovese and Toscano were determined to be the highest, and their height reached up to 70.5 cm. Cultivar Sweet Genovese was the most productive; its fresh herb mass per plant reached up to 0.71 kg under growing in the open field and greenhouse. Higher air temperature and constant watering of the soil in the greenhouse increased the accumulation of essential oils of basil. The biochemical analyses showed that the essential oil amount of 31% was higher when basils were grown in a greenhouse compared to an open field. Keywords: cultivar; fresh herb; morphological traits; Ocimum basilicum L.; productivity 1. Introduction Basil (Ocimum basilicum L.) is grown in many countries of the world, and it is widely used for its medical and aromatic properties [1,2]. These properties are associated with the presence of essential oil in basil. Many studies and conclusions are presented about the composition and peculiarities of essential oil accumulation in basils as well as in other spices and plants with antioxidant properties [3–14]. Chang et al. [15] report the content and amounts of essential oils depending on the age of basil plants. The growth, yield, plant quality, and nutrition of basil under soilless agricultural systems are studied [16–19]. It is proved that the aeroponic system records the highest values of basil roots, shoots and leaves, and essential oil content compared to hydroponic and peat moss slabs [18]. Walters and Currey [17] determine the influence of different hydroponic systems on the efficiency of basil production. One of the latest experiments confirms the effect of genotype and season on the content of ascorbic acid and nitrate levels in plants [19]. Barickman et al. [20] present and the dependence of morphological processes on the air temperature and CO 2 content. Basil is mostly cultivated in the countries with the warmer climate in Tropical America, Africa, Asia, and Southern EU [15,21–23]. It is an annual herb native to India and other parts of Asia [23]. Previous studies have shown that basil is susceptible to growth temperature. Meteorological and growth conditions are one of the most important factors that affect the yield quality and essential oils accumulation of basils [2,5,13]. Temperature below 10 ◦ C Plants 2022, 11, 1896. https://doi.org/10.3390/plants11141896 https://www.mdpi.com/journal/plants