Effects of some leaf-emitted volatile compounds on aphid population increase

Abstract

A role of some volatile compounds produced by plant tissues may be as defensive molecules against various pests, including arthropods. Volatile six-carbon compounds derived in plant tissue from polyunsaturated fatty acids via lipoxygenase/hydroperoxide lyase reduced tobacco aphid fecundity at certain concentrations when added to headspace vapor to which aphids were exposed. Both C6 aldehydes and alcohols were effective, with the alcohols having greater activity. (Z)-3-Hexenyl acetate at levels in the headspace similar to those of the alcohols and aldehydes did not reduce aphid fecundity. A 6-hr exposure period to the C6 aldehydes and alcohols was needed for maximum effect on the aphids feeding on tobacco leaves. Analysis of the direct versus indirect effects of these compounds indicates that the volatile aldehydes had both direct effects on aphid fecundity and indirect effects due to induced changes in the leaves upon which the aphids were feeding, while only indirect effects were observed for the alcohols. Tomato leaves have the capacity to produce volatile compounds at levels that impact aphid population increase, with the volatiles produced from crushed leaves having a much larger effect. The C6 aldehydes and alcohols may be components of the fecundity reduction seen with tomato volatiles; however, volatile terpenes showed no effect. These results can be of significance for the genetic alteration of plants for improved aphid resistance.

Interactions between tomato volatile organic compounds and aphid behaviour

“…The effect of cis-hexen-1-ol on aphid reproduction seems to be variable. In our system there was no effect (Table 2) whilst on tobacco and potato this compound negatively affected the fertility of two Myzus species (Hildebrand et al 1993;Vancanneyt et al 2001). The mobility, in terms of plant uptake, and the specificity of the induction of defence genes, have been reported for cis-hexen-1-ol both in model (lima bean) and crop (maize) plants (Arimura et al 2001;Farag et al 2005) and this makes it an ideal candidate for alternative methods of pest control.…”

Loss of Function of FATTY ACID DESATURASE7 in Tomato Enhances Basal Aphid Resistance in a Salicylate-Dependent Manner

“…Similar shifts in volatile profiles were also observed in Atfad7 Arabidopsis plants (Zhuang et al, 1996), although overall production of C6 volatiles is reported to be extremely low in the Columbia ecotype (Duan et al, 2005;Chehab et al, 2008). HPL appears to contribute to aphid resistance in potato (Vancanneyt et al, 2001), and several VOCs have direct antibiotic effects on aphids in vitro (Hildebrand et al, 1993). However, several lines of evidence suggest that HPL-derived VOCs are not essential to aphid resistance in plants with impaired FAD7 function.…”

Variations in CYP74B2 (Hydroperoxide Lyase) Gene Expression Differentially Affect Hexenal Signaling in the Columbia and Landsberg erecta Ecotypes of Arabidopsis

“…The fact that transcripts from these loci are also induced in herbivoredamaged plants (Reymond et al, 2004) and depleted in the Col ecotype suggests that they also exist downstream of the HPL pathway activated in plant-insect interactions. The immediate effects on insect resistance of inactivating the HPL pathway are complexed by the fact that GLVs have the ability to affect herbivore performance both negatively (by reducing feeding rate, repelling oviposition, or attracting predators; Hildebrand et al, 1993;DeMoraes et al, 2001;Kessler and Baldwin, 2001;Vancanneyt et al, 2001) and positively (by serving as feeding stimulants; Halitschke et al, 2004). Further comparison of the differences in the responses of the Col and Ler ecotypes to herbivore damage will provide more insight into the necessity of having a functional HPL branch in the oxylipin pathway.…”