Abstract
Elicitation of plant defense signaling that results in altered emission of volatile organic compounds (VOCs) offers opportunities for protecting plants against arthropod pests. In this study, we treated potato, Solanum tuberosum L., with the plant defense elicitor cis-jasmone (CJ), which induces the emission of defense VOCs and thus affects the behavior of herbivores. Using chemical analysis, electrophysiological and behavioral assays with the potato-feeding aphid Macrosiphum euphorbiae, we showed that CJ treatment substantially increased the emission of defense VOCs from potatoes compared to no treatment. Coupled GC-electroantennogram (GC-EAG) recordings from the antennae of M. euphorbiae showed robust responses to 14 compounds present in induced VOCs, suggesting their behavioral role in potato/aphid interactions. Plants treated with CJ and then challenged with M. euphorbiae were most repellent to alate M. euphorbiae. Principal component analysis (PCA) of VOC collections suggested that (E)-2-hexenal, (E,E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene (TMTT), (E)-β-farnesene, (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT), methyl salicylate (MeSA), CJ, and methyl benzoate (MeBA) were the main VOCs contributing to aphid behavioral responses, and that production of TMTT, (E)-β-farnesene, CJ, and DMNT correlated most strongly with aphid repellency. Our findings confirm that CJ can enhance potato defense against aphids by inducing production of VOCs involved in aphid-induced signalling.
Highlights
Plants have evolved sophisticated mechanisms against herbivore attack, including production of complex mixtures of volatile organic compounds (VOCs) that directly deter herbivores (Bruce and Pickett 2011; Mithöfer and Boland 2012)
VOC Analyses Gas chromatography (GC) and coupled GCmass spectrometry (GC-MS) analyses of volatile collections from potato plants revealed the presence of 29 detectable VOCs under different treatments (i.e. INTACT plants = neither cis-jasmone (CJ) nor Macrosiphum euphorbiae–infested; CJ = CJ treatment; ME = M. euphorbiae–infested; CJME = CJ treatment infestation afterwards with M. euphorbiae; SUR = surfactant treatment)
Plants have evolved highly effective defense mechanisms to resist being consumed by herbivorous insects in general (Mithöfer and Boland 2012) and aphids in particular (Züst and Agrawal 2016), with these inducible defensive mechanisms being regulated mainly by jasmonic acid (JA), which is the major hormone associated with insect/herbivore responses in terms of the production and release of VOCs (Howe and Jander 2008)
Summary
Plants have evolved sophisticated mechanisms against herbivore attack, including production of complex mixtures of volatile organic compounds (VOCs) that directly deter herbivores (Bruce and Pickett 2011; Mithöfer and Boland 2012). This phenomenon has raised the prospect of manipulating the emission of VOCs to enhance crop protection (Heil 2014; Turlings and Ton 2006). Cis-Jasmone treatment of crop plants induces direct defense against herbivores, and induces indirect defense by releasing VOCs that attract natural enemies (Birkett et al 2000; Bruce et al 2008; Moraes et al 2009; Vieira et al 2013). It should be noted that, in addition to the divergent synthesis of CJ from that of JA, CJ signals differently to JA (Matthes et al 2010, 2011)
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