Characterization of Agrobacterium radiobacter, a new pathogen of pistachio

Crown and stem gall caused by agrobacterial species is one of the most devastating diseases on different crops worldwide. In spring 2018, an alert concerning a disease forming galls on seedlings of pistachio in nurseries was received from Rafsanjan county, Kerman province, Iran. After isolation of bacteria from the galls by using conventional bacteriological methods, bacterial colonies were purified and selected for further analyses including biochemical, pathogenicity and molecular tests. Pathogenicity tests of all isolates on test plants and carrot discs were evaluated positive. Based on the results of biochemical and pathogenicity tests, supported by molecular phylogenies of housekeeping and pathogenicity genes, the isolates were identified as Agrobacterium radiobacter. Since agrobacteria could be easily spread through seedlings and agricultural materials between different areas, the identified Agrobacterium strains could be considered as a latent threat to the pistachio nurseries of Iran. The present study is the first report on the occurrence of crown and stem gall on pistachio caused by A. radiobacter worldwide.Peer reviewe