Field-based Evaluation of a Novel SPME-GC-MS Method for Investigation of Below-ground Interaction between Brassica Roots and Larvae of Cabbage Root Fly, Delia radicum L.
BACKGROUND
Collection of volatiles from plant roots poses technical challenges due to difficulties accessing the soil environment without damaging the roots.


OBJECTIVE
To validate a new non-invasive method for passive sampling of root volatiles in situ, from plants grown under field conditions, using solid phase micro-extraction (SPME).


METHODS
SPME fibres were inserted into perforated polytetrafluoroethene (PTFE) tubes positioned in the soil next to broccoli plants for collection of root volatiles pre- and post-infestation with Delia radicum larvae. After sample analysis by gas chromatography-mass spectrometry (GC-MS), principal component analysis (PCA) was applied to determine differences in the profiles of volatiles between samples.


RESULTS
GC-MS analysis revealed that this method can detect temporal changes in root volatiles emitted before and after Delia radicum damage. PCA showed that samples collected pre- and post-infestation were compositionally different due to the presence of root volatiles induced by D. radicum feeding. Sulphur containing compounds, in particular, accounted for the differences observed. Root volatiles emission patterns post-infestation are thought to follow the feeding and developmental progress of larvae.


CONCLUSIONS
This study shows that volatiles released by broccoli roots can be collected in situ using SPME fibres within perforated PTFE tubes under field conditions. Plants damaged by Delia radicum larvae could be distinguished from plants sampled pre-infestation and soil controls on the basis of larval feeding-induced sulphur-containing volatiles. These results show that this new method is a powerful tool for non-invasive sampling of root volatiles below-ground. Copyright © 2016 John Wiley & Sons, Ltd.
The James Hutton Institute, Invergowrie, Dundee, DD2 5DA, UK.|Scotland's Rural College, Nicholas Kemmer Road, Edinburgh, EH9 3FH, UK.|School of Biological Sciences, The University of Edinburgh, Darwin Building, The King's Buildings, Max Born Crescent, Edinburgh, EH9 3BF, UK.
William
W
Deasy
The James Hutton Institute, Invergowrie, Dundee, DD2 5DA, UK. tom.shepherd@hutton.ac.uk.
Tom
T
Shepherd
Biomathematics and Statistics Scotland, Invergowrie, Dundee, DD2 5DA, UK.
Colin J
CJ
Alexander
The James Hutton Institute, Invergowrie, Dundee, DD2 5DA, UK.
A Nicholas E
AN
Birch
Scotland's Rural College, Nicholas Kemmer Road, Edinburgh, EH9 3FH, UK.
K Andrew
KA
Evans
D000818:Animals; D001937:Brassica / Q000469:parasitology / Q000502:physiology*; D004175:Diptera / Q000254:growth & development / Q000502:physiology*; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D007814:Larva / Q000502:physiology*; D018517:Plant Roots / Q000502:physiology*; D025341:Principal Component Analysis; D052617:Solid Phase Microextraction / Q000379:methods*
Brassica; Delia radicum; Field and soil; SPME-GC-MS; in situ root volatiles analysis