Fig. 1

Symbiotic performance of E. meliloti strains selected for plant transcriptome analysis. Shoot dry weights (a) and nitrogenase activities (b) were measured for four M. sativa cultivars: G9, Gannong No. 9; G3, Gannong No. 3; Q, Qingshui; L, Longzhong. Data are means and standard errors of four biological replicates. Nitrogenase activities were expressed as μmol·g^− 1·h^− 1. Level of significance was indicated by either two stars (P < 0.01) or four stars (P < 0.0001) above the bar. The Student’s t-test was performed in comparison with the uninoculated controls (CK). Effective one- and two-cultivar specificity biotypes (E1 vs. E2) were distinguished by two different colors