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Host control over infection and proliferation of a cheater symbiont
Author(s) -
SACHS J. L.,
RUSSELL J. E.,
LII Y. E.,
BLACK K. C.,
LOPEZ G.,
PATIL A. S.
Publication year - 2010
Publication title -
journal of evolutionary biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.289
H-Index - 128
eISSN - 1420-9101
pISSN - 1010-061X
DOI - 10.1111/j.1420-9101.2010.02056.x
Subject(s) - biology , host (biology) , symbiosis , population , strain (injury) , experimental evolution , inoculation , rhizobia , evolutionary biology , genetics , bacteria , immunology , demography , gene , anatomy , sociology
Host control mechanisms are thought to be critical for selecting against cheater mutants in symbiont populations. Here, we provide the first experimental test of a legume host’s ability to constrain the infection and proliferation of a native‐occurring rhizobial cheater. Lotus strigosus hosts were experimentally inoculated with pairs of Bradyrhizobium strains that naturally vary in symbiotic benefit, including a cheater strain that proliferates in the roots of singly infected hosts, yet provides zero growth benefits. Within co‐infected hosts, the cheater exhibited lower infection rates than competing beneficial strains and grew to smaller population sizes within those nodules. In vitro assays revealed that infection‐rate differences among competing strains were not caused by variation in rhizobial growth rate or interstrain toxicity. These results can explain how a rapidly growing cheater symbiont – that exhibits a massive fitness advantage in single infections – can be prevented from sweeping through a beneficial population of symbionts.