Antibacterial effects of savory essential oil and two copper compounds in control of grape crown gall

During 2005-2006, many grapevine plants and soil samples were collected from Qazvin vineyards for A. tumefaciens. All plant samples have been surface sterilized prior culturing on nutrient agar medium (NA). The soil samples have been cultured on semi-selective D1M medium for ease isolation. All suspected colonies were restreaked on NA for pure culture collections. Based on key biochemical and pathogenicity tests, the crown gall bacterial isolates have been identified as A. tumefaciens. In order to evaluate the effectiveness of 15 plant essential oils and 2 copper compounds i.e. Bordeaux mixture (0.5%) and copper oxychloride (0.3%) against crown gall bacterium, different laboratory, greenhouse and field trails were conducted. Among these, the essential oil of the plant savory (Satureia officinalis) with 9 cm inhibition zones on NA exhibited the most promising antibacterial effect. Similar results were obtained with carrot discs, sunflower seedling assays and also grapevine gall treatments under natural single season field trail. In later case, gall development suppression was doubled compared to two copper compounds. This approach may lead to an alternative control measurement on bacterial crown gall disease management.