M. loti mutants constructed in this study and their symbiotic phenotypes.

aIDM = insertion duplication mutant in which coding sequence disrupted; CMD = cis-merodiploid insertion mutant in which gene is not inactivated as mutant retains wild-type copy of gene including entire promoter region downstream of lacZ fusion (except for JS16 and JS17 in which promoter is truncated).bSymbiotic effectiveness of mutants determined by measuring the wet weights of 15 L. corniculatus seedlings at 6 weeks post-inoculation. Data were compared with those obtained for seedlings inoculated with the wild-type and uninoculated controls. + = Fix+ (fully effective); − = Fix− (ineffective); P = partially effective (see Table 5).