Screening of Two <i>Ocimum</i> <i>tenuiflorum</i> L. (Lamiaceae) Morphotypes for their Morphological Characters, Essential Oil Composition and Fruit Fly Attractant Ability

Abstract

Bactrocera dorsalis (Hendel) (Diptera: Tephritidae) is the destructive pest of over 300 cultivated and wild fruits all over the world. Present study describes the morphology, essential oil content and composition and bioassay on fruit fly attractant ability of essential oil of two Ocimum tenuiflorum morphotypes (MT1 purple and MT2 purple-green) grown in Sri Lanka. Four months old, O. tenuiflorum aerial parts were hydro-distilled for 4 h. GC-MS analysis of essential oils and bio-assay for B. dorsalis attractant ability was performed using previously established methodologies. The yield of the essential oils of O. tenuiflorum MT1 and MT2 were 1.51±0.02% and 1.45±0.01% (v/w), respectively. Eighteen compounds were identified, which encountered over 97% of the oil constituents. The main constituents found in the oil of MT1 were methyl eugenol (72.50±1.03%) followed by β-caryophyllene (17.53±2.0%), germacrene D (1.55±0.10%), β-elemene (2.46±0.17%), while methyl eugenol (64.23±2.43%), β-caryophyllene (13.29±2.18%), β-elemene (6.94±1.41%), germacrene D (2.47±0.96%), were from extracted from MT2. Bioassays conducted on essential oils of MT1, MT2 and purified Methyl Eugenol demonstrated that the B. dorsalis attractant ability of essential oil MT1 (106±8.1), MT2 104±2 and commercial Methyl Eugenol (111±8.5) was not significantly different during the first week of the experiment. Results of our study open an avenue for use of essential oil of Ocimum tenuiflorum as potential natural para pheromone source for fruit fly control and monitoring in fruit industry in Sri Lanka.