Mapping the genetic basis of symbiotic variation in legume-rhizobium interactions in medicago truncatula

Amanda J. Gorton, Katy D. Heath, Marie Laure Pilet-Nayel, Alain Baranger, John R. Stinchcombe

Research output: Contribution to journalArticlepeer-review


Mutualisms are known to be genetically variable, where the genotypes differ in the fitness benefits they gain from the interaction. To date, little is known about the loci that underlie such genetic variation in fitness or whether the loci influencing fitness are partner specific, and depend on the genotype of the interaction partner. In the legume-rhizobium mutualism, one set of potential candidate genes that may influence the fitness benefits of the symbiosis are the plant genes involved in the initiation of the signaling pathway between the two partners. Here we performed quantitative trait loci (QTL) mapping in Medicago truncatula in two different rhizobium strain treatments to locate regions of the genome influencing plant traits, assess whether such regions are dependent on the genotype of the rhizobial mutualist (QTL × rhizobium strain), and evaluate the contribution of sequence variation at known symbiosis signaling genes. Two of the symbiotic signaling genes, NFP and DMI3, colocalized with two QTL affecting average fruit weight and leaf number, suggesting that natural variation in nodulation genes may potentially influence plant fitness. In both rhizobium strain treatments, there were QTL that influenced multiple traits, indicative of either tight linkage between loci or pleiotropy, including one QTL with opposing effects on growth and reproduction. There was no evidence for QTL × rhizobium strain or genotype × genotype interactions, suggesting either that such interactions are due to small-effect loci or that more genotype-genotype combinations need to be tested in future mapping studies.

Original languageEnglish (US)
Pages (from-to)1291-1303
Number of pages13
JournalG3: Genes, Genomes, Genetics
Issue number11
StatePublished - Nov 2012


  • G × G genotype by
  • Genotype
  • Interactions
  • Interactions between species (Bronstein 2001) that affect many ecological and evolutionary
  • Meliloti Mutualisms, or interspecific cooperation, are reciprocally beneficial
  • Nod factor
  • QTL mapping
  • Signaling
  • Sinorhizobium

ASJC Scopus subject areas

  • Molecular Biology
  • Genetics
  • Genetics(clinical)


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