LAUSR

Endophytic bacteria have attracted a great attention because they produce chemicals that increase the resistance of host plants against diseases. In the current study, 40 strains of endophytic bacteria from Kobreasia capillifolia of an alpine grassland were screened for the inhibitory effect against the tomato leaf pathogen Pseudomonas syringae. The endophytic bacterium strain 262XY2’ developed a clear inhibition zone of growth with a bacteriostatic band width of 0.67 cm against P. syringae on the cultural plates. The strain 262XY2’ also showed an inhibitory activity to Bipolaris sorokiniana, Stysanus stemonitis, Alternaria soloni, Botrytis cinerea, Fusarium solani and F. oxysporum. It was able to fix nitrogen, dissolve phosphorus and produce indole 3-acetic acid (IAA). Based on morphological characteristics and the molecular sequence analyses of 16S rRNA and gyrB genes, the 262XY2’ strain was identified as Bacillus subtilis. B. subtilis 262XY2’ strain tagged with the green fluorescence protein (GFP) was found to colonize stably in the roots, stems and leaves of tomato plants, and could be re-isolated from the rhizosphere soil after 0 to 60 days of inoculation. Moreover, it also exhibited a control effect of 48.55% against tomato leaf spot caused by P. syringae. Our results indicate that the antagonistic bacteria B. subtilis 262XY2’ has the potential to be used as a biocontrol agent for tomato leaf spot.