Figure 1

Symbiotic properties of Bradyrhizobium vignae ORS3257 strain (WT) and its derivative T3SS mutant (∆T3SS) in different Vigna species. (a–c) Comparison of the growth of the plants (aerial part), non-inoculated (NI) or inoculated with ORS3257 wild-type strain (WT) or its derivative T3SS mutant (∆T3SS) at 21 days after inoculation; (d–f) Leaf chlorophyll content; (g–i) Plant dry weight; (j–l) Number of nodules per plant. The experiment was carried out in duplicate with five plants per condition. *P < 0.05, **P < 0.01, and ***P < 0.001, significant differences between WT ORS3257 and the T3SS mutant using a nonparametric Kruskal–Wallis test. (m–x) View of the root and the nodules induced by ORS3257 strain and its derivative T3SS mutant (∆T3SS). (Scale bars, m to r, 1 cm; s to x, 2 mm). (y–ah) Cytological analysis of the nodules induced by strain WT ORS3257 and ∆T3SS observed by confocal microscopy after staining with SYTO 9 (green: live bacteria), calcofluor (blue: plant cell wall), and propidium iodide (red; infected plant nuclei and dead bacteria or bacteria with compromised membranes). (Scale bars, y to ac, 200 µm; ad to ah, 50 µm). White arrowhead in AB shows the necrotic zone.