Inoculum type does not affect overall resistance of an arbuscular mycorrhiza-defective tomato mutant to colonisation but inoculation does change competitive interactions with wild-type tomato

Authors

  • T. R. Cavagnaro,

    Corresponding author
    1. Centre for Plant Root Symbioses, Soil and Land Systems, School of Earth and Environmental Sciences and
    2. Plant and Pest Sciences, School of Agriculture and Wine, Waite Campus, The University of Adelaide, Adelaide, South Australia 5005, Australia;
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  • F. A. Smith,

    1. Centre for Plant Root Symbioses, Soil and Land Systems, School of Earth and Environmental Sciences and
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  • G. Hay,

    1. Centre for Plant Root Symbioses, Soil and Land Systems, School of Earth and Environmental Sciences and
    2. Present address: Environmental Biology, School of Earth and Environmental Sciences, The University of Adelaide, Adelaide, South Australia 5005, Australia
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  • V. L. Carne-Cavagnaro,

    1. Plant and Pest Sciences, School of Agriculture and Wine, Waite Campus, The University of Adelaide, Adelaide, South Australia 5005, Australia;
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  • S. E. Smith

    1. Centre for Plant Root Symbioses, Soil and Land Systems, School of Earth and Environmental Sciences and
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Author for correspondence: Timothy R. Cavagnaro Tel: +530 7522171 Fax: +530 752 1552 Email: trcavagnaro@ucdavis.edu

Summary

  • • The influence of inoculum type on colonisation of a mycorrhiza-defective tomato mutant, rmc, by the AM fungus Glomus coronatum was studied by comparing inoculum composed predominantly of spores with hyphae growing from mycorrhizal ‘nurse plants’, including the wild-type tomato progenitor (WT), other Lycopersicon species, and leek.
  • • Colonisation of rmc was not primarily influenced by inoculum source; minor differences could be attributed to differences in inoculum potential. The mutation is therefore different from other mycorrhiza-defective tomato mutants.
  • • Growth of rmc was reduced in the presence of nurse plants, because of competition with them, so a second experiment examined the effects of AM colonisation on competition between rmc and the WT tomato. This experiment was a replacement series in which rmc and WT were grown in competition and as single plants, inoculated with G. coronatum or uninoculated.
  • • The WT did not respond to G. coronatum when grown alone, but responded positively when in competition with rmc. We conclude from the second experiment that mycorrhizal responsiveness is influenced by competition with (in this case) a surrogate nonhost plant rmc in a situation that mimics interspecific competition. It is therefore a community-based parameter. Results are discussed in the context of responses of mycorrhizal vs nonmycorrhizal species and competition in natural plant ecosytems.

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