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Oecologia

Title:		Induced plant defense via volatile production is dependent on rhizobial symbiosis
Author(s):		Ballhorn DJ; Kautz S; Schadler M;
Address:		"Department of Biology, Portland State University, Portland, OR 97201, USA. ballhorn@pdx.edu"
Journal Title:		Oecologia
Year:		2013
Volume:		20121216
Issue:		3
Page Number:		833 - 846
DOI:		10.1007/s00442-012-2539-x
ISSN/ISBN:		1432-1939 (Electronic) 0029-8549 (Linking)
Abstract:		"Nitrogen-fixing rhizobia can substantially influence plant-herbivore interactions by altering plant chemical composition and food quality. However, the effects of rhizobia on plant volatiles, which serve as indirect and direct defenses against arthropod herbivores and as signals in defense-associated plant-plant and within-plant signaling, are still unstudied. We measured the release of jasmonic acid (JA)-induced volatiles of rhizobia-colonized and rhizobia-free lima bean plants (Fabaceae: Phaseolus lunatus L.) and tested effects of their respective bouquets of volatile organic compounds (VOCs) on a specialist insect herbivore (Mexican bean beetle; Coccinellidae: Epilachna varivestis Mulsant) in olfactometer choice trials. In a further experiment, we showed that VOC induction by JA reflects the plant responses to mechanical wounding and insect herbivory. Following induction with JA, rhizobia-colonized plants released significantly higher amounts of the shikimic acid-derived compounds, whereas the emission of compounds produced via the octadecanoid, mevalonate and non-mevalonate pathways was reduced. These changes affected the choice behavior of beetles as the preference of non-induced plants was much more pronounced for plants that were colonized by rhizobia. We showed that indole likely represents the causing agent for the observed repellent effects of jasmonic acid-induced VOCs of rhizobia-colonized lima bean plants. Our study demonstrates a rhizobia-triggered efficacy of induced plant defense via volatiles. Due to these findings, we interpret rhizobia as an integral part of legume defenses against herbivores"
Keywords:		Gas Chromatography-Mass Spectrometry Phylogeny Plants/*microbiology Rhizobium/classification/*physiology *Symbiosis Volatile Organic Compounds/*metabolism;
Notes:		"MedlineBallhorn, Daniel J Kautz, Stefanie Schadler, Martin eng Research Support, Non-U.S. Gov't Germany 2012/12/18 Oecologia. 2013 Jul; 172(3):833-46. doi: 10.1007/s00442-012-2539-x. Epub 2012 Dec 16"