Screening of endophytic bacteria isolated from domesticated and wild growing grapevines as potential biological control agents against crown gall disease

Crown gall caused by Agrobacterium tumefaciens and Allorhizobium vitis is an important disease of grapevine worldwide. Both pathogens were isolated from infected grapevines cultivated in Iran and identified by 16S rRNA sequence analysis. A total of 314 endophytic bacteria were isolated from the root, leaves, shoots and fruits of domestic and wild growing grapevines collected from various locations of Kurdistan and West Azerbaijan Provinces. Selected strains further identified by nucleotide sequencing of the 16S rRNA gene belonged to known genera including Pseudomonas, Erwinia, Pantoea, Serratia, Enterobacter and Micrococcus. These strains were screened for their antagonistic effects on both pathogens in vitro as well as their ability to reduce gall formation in planta. In total, 17 strains were able to prevent the growth of both or one of the pathogens under in vitro condition. Among them, Pseudomonas sp. Sn48, Pseudomonas sp. Ba35 and Pantoea sp. Sa14 strains significantly reduced the size of galls in grapevine plantlets. To the best of our knowledge, this study is the first report on the diversity of endophytic bacteria of grapevines with biological control potential against crown gall disease in Iran.