FIG. 2.

Mean dry aerial biomass (± standard error) (a) and mean nodule number (± standard error) (b) obtained for each plant line-bacterial genotype combination. The four S. medicae (md1 to md4) and the eight S. meliloti (ml1 to ml8) strains were inoculated separately on each M. truncatula line. “S. medicae” and “S. meliloti” indicate the results of the two mixtures including all the strains for each species, and “interspecific” is the result of a mixture including one strain of each species (see the text). “control −” is the negative control (no inoculation), and “control +” is the positive control (5 mM nitrogen).