A specialist root herbivore reduces plant resistance and uses an induced plant volatile to aggregate in a density-dependent manner

Robert, Christelle A. M.; Erb, Matthias; Hibbard, Bruce E.; Wade French, B.; Zwahlen, Claudia; Turlings, Ted C. J.; Thompson, Ken (2012). A specialist root herbivore reduces plant resistance and uses an induced plant volatile to aggregate in a density-dependent manner. Functional Ecology, 26(6), pp. 1429-1440. British Ecological Society 10.1111/j.1365-2435.2012.02030.x

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1.Leaf-herbivore attack often triggers induced resistance in plants. However, certain specialist herbivores can also take advantage of the induced metabolic changes. In some cases, they even manipulate plant resistance, leading to a phenomenon called induced susceptibility. Compared to above-ground plant-insect interactions, little is known about the prevalence and consequences of induced responses below-ground.

2.A recent study suggested that feeding by the specialist root herbivore Diabrotica virgifera virgifera makes maize roots more susceptible to conspecifics. To better understand this phenomenon, we conducted a series of experiments to study the behavioural responses and elucidate the underlying biochemical mechanisms.

3.We found that D. virgifera benefitted from feeding on a root system in groups of intermediate size (3–9 larvae/plant in the laboratory), whereas its performance was reduced in large groups (12 larvae/plant). Interestingly, the herbivore was able to select host plants with a suitable density of conspecifics by using the induced plant volatile (E)-β-caryophyllene in a dose-dependent manner. Using a split root experiment, we show that the plant-induced susceptibility is systemic and, therefore, plant mediated. Chemical analyses on plant resource reallocation and defences upon herbivory showed that the systemic induced-susceptibility is likely to stem from a combination of (i) increased free amino acid concentrations and (ii) relaxation of defence inducibility.

4.These findings show that herbivores can use induced plant volatiles in a density-dependent manner to aggregate on a host plant and change its metabolism to their own benefit. Our study furthermore helps to explain the remarkable ecological success of D. virgifera in maize fields around the world.

Item Type:	Journal Article (Original Article)
Division/Institute:	08 Faculty of Science > Department of Biology > Institute of Plant Sciences (IPS) 08 Faculty of Science > Department of Biology > Institute of Plant Sciences (IPS) > Biotic Interactions
UniBE Contributor:	Robert, Christelle Aurélie Maud, Erb, Matthias
Subjects:	500 Science > 580 Plants (Botany)
ISSN:	0269-8463
Publisher:	British Ecological Society
Language:	English
Submitter:	Peter Alfred von Ballmoos-Haas
Date Deposited:	14 Jul 2015 07:53
Last Modified:	05 Dec 2022 14:48
Publisher DOI:	10.1111/j.1365-2435.2012.02030.x
Uncontrolled Keywords:	defence inducibility relaxation; Diabrotica virgifera virgifera; induced susceptibility; resource reallocation; root–herbivore interactions; Zea mays
URI:	https://boris.unibe.ch/id/eprint/70248