Abstract:Common eight wheat cultivars were selected and the sensitive cultivars were screened out through gnotobiotic condition test in the laboratory after infecting of the Azorhizobium caulinodans ORS571 (A.caulinodans) to wheat seeds. Infection method of seed soaking, the density of A.caulinodans and adding glucose are also studied, and the colonization of green fluorescence protein (GFP)-labeled A.caulinodans in the wheat seedling were detected by fluorescence microscope. The results show that Xiaoyan22 is the most sensitive wheat cultivar to A.caulinodans, in the gnotobiotic condition the root length and shoot height are increased by 17.04% and 8.37% respectively compared to the control, the optimum dilution proportion of A.caulinodans is 1.0×108/mL, and it is helpful for the infection to add 1g/L glucose in A.caulinodans PBS solution. With fluorescence microscope detection the result shows that GFP-labeled A.caulinodans infects from wheat seeding root hairs and lateral root fractures, and it can colonize in the vascular bundle of root. The field test shows that there is obvious promotion for wheat growth after infecting wheat cultivars seeds with A.caulinodans.