**5.2** *X. arboricola pv fragariae***, Bacterial leaf blight**

Bacterial leaf blight disease is caused by *X. arboricola pv fragariae* (*Xaf*). The disease was first observed on strawberry plants in northern Italy in 1993 [94]. The causative agent was reported as a new pathogen [95]. *Xaf* was determined as a quarantine organism in 2002 [96]. In 2007, it was removed quarantine list by EPPO (The European and Mediterranean Plant Protection Organization) [97]. *Xaf* reported on strawberry plants in Turkey [98]. Both *Xaf* and *X. fragariae* were reported to cause angular leaf spot or bacterial leaf blight symptoms infections on strawberry tissue [99]. Early leaf lesions of *X. arboricola* pv *fragariae* were not water-soaked on the contrary of *X. fragariae*. Disease caused dry, brown leaf spots. These lesions are large brown colored and V-shaped along the leaf margin and veins. İnfected leaves completely become wilted and turn completely yellow colored. The disease did

not affect flowers, peduncles, or fruits of strawberry plants [100]. *X. arboricola* pv *fragariae* (*Xaf*) is gram-negative bacterium. The bacteria are obligate aerobes. On NA growth medium, colonies are yellow, glistening, circular, convex, 1 mm diameter. On YPGA-medium, colonies are yellow, glistening, mucoid, convex, or pulvinate, 1–3 mm diameter. Bacterial cells are 1.7–1.9 μm length, 0.5–0.65 μm width in size. Bacteria causes soft rot of potato slices. It is negative in the arginine dihydrolase test and positive in inducing HR on tobacco plant. The maximum growth temperature was determined as 39°C. Assimilation of glycerol, D-trehalose, L-glutamic acid, maltose, L-fucose, succinic acid, cellobiose, Tween-80, and D-galactose are determined as positive. *Xanthomonas arboricola* pv. *fragariae* is positive in the hydrolyzation of gelatin, esculin, and starch. Molecular (Real-time PCR assay) and Serological (indirect immunofluorescence, ELISA) tests are developed for the detection of strawberry bacterial blight pathogen (*Xaf*). PCR test (Xaf pep) was designed by replicating the pep-prolyl endopeptidase gene region (unique to Xaf) [101]. There is no effective control method of X*. arboricola* pv *fragariae* (*Xaf*). Because of the latent infections, routine testing of strawberry plant propagation material is recommended for preventing possible disease occurrence [98].
