FIG 4.

The relative competitive ability of TA1 wild type and nodD mutant strains. The percentage of nodules occupied by each strain was determined by the presence of blue/nonblue nodules following staining of white clover roots inoculated with pairs of strains in a 1:1 ratio (approximately 500 cells of each strain). The proportion of blue nodules from each comparison is reported as percentage. The same pairs of strains containing reciprocal reporter plasmids are linked by bar color. In each reciprocal combination, the strain lacking pAMNHCELB contained the plasmid pAMNHGUSA. The percentage indicates the proportion of blue nodules determined from the sum of the five uppermost nodules formed on 10 plants (50 nodules total where 5 nodules were present). Three to four sets of 10 plants per strain pair were examined, with each replicate set represented by a symbol. The error bars represent ± the SEM. The asterisks indicate significant difference between the reciprocal pairs of strains (one-way ANOVA with Sidak’s multiple comparisons post hoc test, ***, P < 0.001; ****, P < 0.0001).