Identification of soil inhabiting bacteria in Qazvin province vineyards and investigation of their inhibitory effect on Rhizobium vitis, the causal agent of grape root and crown gall

Root and crown gall caused by Rhizobium vitis, is one of the most important diseases of grapevine worldwide. Although there is no efficient chemical control for the disease, various antagonistic bacteria have been studied for its biocontrol. This study was conducted to identify soil inhabiting bacteria in Qazvin province vineyards and to investigate their inhibitory effect on the pathogen. Samples were collected from soil, as well as grape root and crown in 22 areas over the province. Two hundred ten bacterial isolates, obtained from the samples, were grouped and 73 isolates were selected for further study. Identification of the isolates was performed using physiological and biochemical tests. Also, primers Bsub5F and Bsub3R were used to confirm identification of isolates resembling Bacillus subtilis. Ability of the isolates for antibiotic, siderophore, hydrogen cyanide and protease production was studied. Primer pairs PhI2a/PhI2b and PM2/PM7-26R were used to detect PhID and hcnABC genes respectively in fluorescent psuedomonds. Antagonistic effect of five strains, selected from the identified bacteria, on the pathogen was studied on carrot and turnip slices. Based on the results, antagonistic bacteria belonged to Pseudomonas fluorescens biovar I, III and IV, as well as B. subtilis. All strains produced antibiotic and inhibited growth of the pathogen. Also, strains identified as P. fluorescens biovar I، III and IV produced hydrogen cyanide and protease; however, it differed in siderophore production. PhID and hcnABC genes were detected in strains belonging to P. fluorescens biovar I and IV. Two strains belonging to P. fluorescens biovar I, one P. fluorescens biovar IV strain and two B. subtilis strains inhibited gal formation by Rh. vitis on carrot and turnip slices.