Abstract
The composition and nematicidal activity of the essential oils from the leaves of native and six cultivated varieties of P. microphyllus are reported. Twenty-nine compounds were identified (86.2% sesquiterpenes and 13.8% aliphatic ketones) of which (E)-caryophyllene, germacrene-D, caryophyllene oxide, 2-tridecanone, and 1-hydroxy-2-tridecanone were found in all of the analyzed oils. The nematicidal activity of all the oils was evaluated against the second-stage juvenile nematode Meloidogyne incognita. Essential oils from native P. microphyllus and varieties Xingu and Linha V showed high nematicidal activity, while no activity was found for the other oils. This result was associated with the high concentrations of both 2-tridecanone and 1-hydroxy-2-tridecanone in the active oils. Both ketones were isolated from one of the active oils and showed 100% activity at 1000 ppm concentration.