Essential oils as anti-nematode agents and their influence on in vitro nematode

Tese de doutoramento, Biologia (Biotecnologia), Universidade de Lisboa, Faculdade de Ciências, 2015Parasitic nematodes are among the most production-limiting plant pests. In Europe, the recent introduction of Bursaphelenchus xylophilus [the pinewood nematode (PWN)] and some species of Meloidogyne has proved damaging to forest ecosystems and crop production. Due to the very laborious and environment-dependent nature of greenhouse or field assays, in vitro host with parasite co-cultures can be a useful biotechnological tool to evaluate potential nematotoxic essential oils (EOs). The present work intended to a) screen EOs against PWN motility and M. chitwoodi [Columbia root-knot nematode (CRKN)] hatching, b) establish and characterize Pinus pinaster (maritime pine) in vitro cultures and Solanum tuberosum (potato) hairy roots (HR) cultures as well as P. pinaster with PWN and S. tuberosum HR with CRKN co-cultures, c) determine the effect of selected nematotoxic EOs on co-cultures growth or relative water content, nematode population and volatiles production. Ruta graveolens, Satureja montana and Thymbra capitata EOs revealed high activities against PWN. These and Dysphania ambrosioides and Filipendula ulmaria EOs also showed high inhibitory activity against CRKN. The established P. pinaster with PWN and S. tuberosum HR with CRKN co-cultures, displayed infection and developmental characteristics similar to those in nature. Of the most active EOs, those of R. graveolens and S. montana were chosen to be tested with in vitro co-cultures. S. montana EO was highly phytotoxic to both co-cultures, inhibiting potato HRs growth and inducing chlorosis and wilting in pine shoots. R. graveolens EO inhibited potato HRs with CRKN co-cultures growth but induced no macroscopic damages to in vitro P. pinaster with PWN co-cultures. In addition to constitutive compounds, biotransformation volatile compounds were detected after EOs addition to both co-cultures types. P. pinaster with PWN and S. tuberosum HR with CRKN co-cultures were a good system to mimic some of the natural infection conditions, allowing an overview of the combined host / parasite reactions, and being able to assist in the evaluation of EOs phytotoxicity and nematotoxic potential.Fundação para a Ciência e a Tecnologia (FCT), SFRH/BD/43738/2008, Pest-OE/EQB/LA0023/2011, PTDC/AGR-CFL/117026/201