Page Banner

United States Department of Agriculture

Agricultural Research Service

Research Project: IMPACT OF CLIMATE CHANGE ON PLANT DEFENSE RESPONSES INDUCED BY INSECT HERBIVORES AND PLANT PATHOGENS

Location: Chemistry Research Unit

Title: Root zone chemical ecology: new techniques for below grounf sampling and mass spectrometric analyses of volatile semiochemicals

Authors
item Alborn, Hans
item Kaplan, Fatma -
item Ali, J -

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: July 18, 2013
Publication Date: N/A

Technical Abstract: The ban of methyl bromide as a soil fumigant has led to an urgent need to develop novel methods of control of soil-dwelling pests. The use of semiochemicals for below-ground insect and nematode control is one such novel avenue of research. New technologies to study semiochemically mediated below-ground plant-insect-nematode-microorganism interactions are critically needed. It is now well documented that roots of many plants release volatile organic compounds (VOCs) in response to herbivore damage and that these volatiles attract entomopathogenic nematodes. Recent research indicates that plant pathogenic nematodes also respond to root (or rhizosphere) volatiles. Above ground, similar VOCs governing multitrophic interactions are well known and are studied using established techniques; however, in contrast to the release of leaf or floral VOCs into a dynamic and constantly changing airspace, root VOCs are released into a virtually static airspace within the soil. Consequently, even VOCs that might be released at a very low rate, or for a short time, will accumulate in the soil surrounding the root and then disperse through the soil airspace solely by diffusion. Root-related VOCs have typically been sampled either by transferring a plant, or just its roots, from a pot to an artificial environment and then drawing most of the air surrounding the roots through an adsorption filter that trap VOCs, or by maceration and solvent extraction of the roots. However, more sensitive and less intrusive sampling is necessary for in vivo studies of below-ground interactions governed by volatile semiochemicals. To accomplish this, probes were designed for direct in-soil sampling that, in combination with improved thermal desorption GC/MS analyses, allow short sampling times and require removal of minimal air volumes. This makes it possible to monitor continuously below-ground release of VOCs without significantly affecting the system. Low impact sampling will also make it possible to follow the dynamics of VOCs induced in response to insect or nematode infestation and to distinguish these from constitutively released VOCs.

Last Modified: 10/1/2014