¹Ecology, Evolution and Behavior, University of Minnesota, Minneapolis, MN, USA

Correspondence: WC Ratcliff, Ecology, Evolution and Behavior, University of Minnesota, 100 Ecology Building, 1987 Upper Buford Circle, St Paul, MN 55108, USA.E-mail: ratcl009@umn.edu

Received 13 January 2009; Revised 11 March 2009; Accepted 11 March 2009; Published online 9 April 2009.

Abstract

Legume sanctions against rhizobia that fix less nitrogen should exert a strong selection for more beneficial genotypes of rhizobia, but strains providing little host benefit are common. One reason may be that some rhizobia chemically manipulate the host, undermining the efficacy of sanctions. Here we show that the ethylene inhibitor, rhizobitoxine (Rtx), is an example of such a manipulation. Rtx-producing rhizobia decreased legume growth, but benefited relative to an isogenic, non-producing strain on the same plant by accumulating 47% more of the storage lipid poly-3-hydroxybutyrate (PHB).