Day-time variations in essential oil contents of sweet basil (Ocimum basilicum L.) ecotypes in semi-arid climatic conditions

Abstract

Sweet basil is a tropical herbaceous plant valued for essential oil containing over 200 compounds. This study aimed to determine the optimal harvest time to harvest maximum essential oil and linalool yields in hot Southeast Anatolian conditions of Turkey, using two ecotypes, Dicle and Silbe, planted in Medicinal Plants Collection Garden, of Dicle University. The plants were harvested at five intervals of three hours duration from 06:00 to 18:00. Their dried leaves were hydrodistilled for extraction of essential oil, which was subjected to GC-MS analysis to determine the variance in chemical compounds composition. The results showed significant variations in essential oil contents, which fluctuated due to diurnal changes in temperature and humidity. The Dicle ecotype exhibited the highest essential oil contents after the 2nd cutting, The Silbe ecotype had the minimum essential oil after first cutting. The interaction between harvest times and ecotypes significantly affected oil yields. A biplot analysis revealed a two-dimensional PCA score (51.15% and 25.29%) for the Dicle ecotype, indicating a total variation rate of 76.44%. The study underscores the responsible factors in maximizing basil essential oil. It also indicated presence of 50-65% linalool and methyl chavicol in essential oil analyzed from the two O. basilicum ecotypes.