An outbreak of crown gall disease on rose caused by Agrobacterium tumefaciens in Turkey

Cultivars of roses (Rosa spp.) are grown in greenhouses in Mediterranean region of Turkey from November to June for local and international markets. During March and June of 2002, nearly 40% of rose plants in six different greenhouses in the provinces of Mersin and Adana were observed with crown gall symptoms on various parts, particularly in the crown (Fig 1).

A non-fluorescent gram-negative bacterium was consistently isolated from diseased tissues onto King's B medium (King et al., 1954). Twenty-five representative strains isolated were aerobic, non-sporing, non-pigmented, motile, rod-shaped, oxidase negative and catalase positive. Fatty acid analysis identified the strains as Agrobacterium tumefaciens Smith & Townsend with similarity indices ranging from 72 to 91% (Bouzar et al., 1993). Pathogenicity of the strains was confirmed on five week-old tomato plants (cv. H-2274) with needle inoculation of bacterial suspensions containing 10⁸ CFU/ml in 0.85% saline (Fig 2). Inoculated and control (saline injected) plants were maintained in the growth chamber for 8 days at 25 ° C and 70% RH. Gall symptoms similar to those observed in the greenhouses developed on the inoculated plants within 5-7 days. No symptoms developed on control plants. The bacterium was reisolated from inoculated plants and identified as A. tumefaciens. This is the first report of the occurrence and outbreak of a crown gall disease caused by this bacterium on rose cultivars grown in Turkey.