ARS | Publication request: Subterranean, herbivore-induced plant volatile increases biological control activity of multiple beneficial nematode species in distinct habitats

Submitted to: PLoS One
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 1, 2012
Publication Date: June 15, 2012
Citation: Ali, J.G., Alborn, H.T., Campos-Herrera, R., Kaplan, F., Duncan, L.W., Rodriquez-Saona, C., Koppenhofer, A.M., Stelinski, L.L. 2012. Subterranean, herbivore-induced plant volatile increases biological control activity of multiple beneficial nematode species in distinct habitats. PLoS One. 7(6):1-8.

Interpretive Summary: While the role of herbivore-induced volatiles in plant-herbivore-natural enemy interactions is well documented aboveground, new evidence suggests that belowground volatile emissions can protect plants in a similar way. In collaboration with Scientists at University of Florida, Citrus Research and Education Center, Lake Alfred Florida and Department of Entomology, Rutgers University, New Brunswick, NJ. Scientists at United States Department of Agriculture, Agricultural Research Center, Center for Medical, Agricultural, and Veterinary Entomology in Gainesville, FL discovered that belowground herbivore-induced volatiles can enhance mortality of agriculturally significant root pests by attracting beneficial entomopathogenic nematodes (EPNs). It was shown in real time that 9-12 hours after initiation of larval Diaprepes abbreviatus feeding, citrus roots released a terpene, identified as pregeijerene (1,5-dimethylcyclodeca-1,5,7-triene). By the use of a novel sampling technique, pregijerene was also shown to be released by mature citrus trees in the field. In citrus orchard field tests pregeijerene was shown to attracted native EPNs and increase mortality of beetle larvae (D. abbreviatus) compared to controls. Quantitative real-time PCR revealed that pregeijerene increased pest mortality by attracting four species of naturally occurring EPNs in the field. The generality of this root-zone signal was also tested by application of pregeijerene in blueberry fields where mortality of root pest larvae (Galleria mellonella and Anomala orientalis) again increased by the attraction of naturally occurring populations of an EPN. Thus, this specific belowground signal attracts natural enemies of widespread root pests in distinct agricultural systems and thus may have broad potential in biological control of root pests.

Technical Abstract: While the role of herbivore-induced volatiles in plant-herbivore-natural enemy interactions is well documented aboveground, new evidence suggests that belowground volatile emissions can protect plants by attracting entomopathogenic nematodes (EPNs). However, due to methodological limitations, no study has previously detected belowground herbivore-induced volatiles in the field or quantified their impact on attraction of diverse EPN species. Here we show how a belowground herbivore-induced volatile can enhance mortality of agriculturally significant root pests. First, in real time, we identified pregeijerene (1,5-dimethylcyclodeca-1,5,7-triene) from citrus roots 9-12 hours after initiation of larval Diaprepes abbreviatus feeding. This compound was also detected in the root zone of mature citrus trees in the field. Application of collected volatiles from weevil-damaged citrus roots attracted native EPNs and increased mortality of beetle larvae (D. abbreviatus) compared to controls in a citrus orchard. In addition, field applications of isolated pregeijerene caused similar results. Quantitative real-time PCR revealed that pregeijerene increased pest mortality by attracting four species of naturally occurring EPNs in the field. Finally, we tested the generality of this root-zone signal by application of pregeijerene in blueberry fields; mortality of larvae (Galleria mellonella and Anomala orientalis) again increased by attracting naturally occurring populations of an EPN. Thus, this specific belowground signal attracts natural enemies of widespread root pests in distinct agricultural systems and may have broad potential in biological control of root pests.