Antibacterial effects of eucalyptus and some commercial plant essential oils on tomato bacterial canker disease (Clavibacter michiganensis subsp. michiganensis)

Clavibacter michiganensis subsp. michiganensis is a Gram-positive, seed borne, and quarantine bacterium which causes bacterial wilt and cancer disease in tomato. This study was conducted to determine in vitro antibacterial activity of commercial plant essential oils of eucalyptus (Eucalyptus citriodora), St. John's wort (Hypericum perforatum), clove (Dianthus caryophyllus), anise seed (Pimpinella anisum) and mustard (Brassica nigra) on C. michiganensis subsp. michiganensis. In this study, morphological and molecular diagnostic assays were performed on suspicious samples collected from Mersin province and as a result six of them were identified as C. michiganensis subsp. michiganensis. The most effective essential oil on C. michiganensis subsp. michiganensis was determined by disc-diffusion method under in vitro conditions and the inhibition zone diameters were measured. Since eucalyptus essential oil was determined as the most efficient essential oil, the most effective concentration was also determined by applying different amount of essential oils on the antibiogram discs and measuring inhibition zones. The most effective dose was found to be 25 μl which caused 23 mm inhibition zone. This concentration was also applied on tomato plants in different combinations. Based on these results, it can be concluded that eucalyptus essential oils can be used for management of control strategies on C. michiganensis subsp. michiganensis