In Montenegro, stone fruit species are grown on intensive and semi-intensive commercial plantations. However, almond production is mainly organized on family gardens and for household consumption. During two seasons (2017–2018), we surveyed apricot, peach, nectarine, sweet cherry, Japanese plum, and almond orchards for the presence of bacterial diseases at different geographical locations in Montenegro. From leaf, petiole and fruit lesions, branch or twig cankers, and necrotizing buds, a total of 29 isolates were obtained and subjected to identification based on their morphological, pathogenic, biochemical, and molecular characteristics. Pathogenicity of the isolates was confirmed by reproducing the symptoms on leaves, fruits, and twigs of the corresponding host plants. The biochemical tests indicated that the isolates belong to Pseudomonas syringae. However, isolates’ characterization showed variation in their phenotypic and molecular features. The presence of the syrB gene and ice nucleation activity grouped most of the isolates within pathovar syringae. The results of rep-PCR using the BOX primer revealed high genetic diversity of isolates. Multilocus sequence analysis (MLSA), using four housekeeping genes, showed that 27 isolates belong to the genomic species 1, P. syringae sensu stricto, corresponding to P. syringae phylogroup 2. However, isolates from the same phylogroup 2 did not form a monophyletic group. One strain isolated from apricot was most distinct and similar to members of genomic species 2, phylogroup 3. All tested isolates showed significant levels of resistance to copper sulfate and high level of sensitivity to streptomycin sulfate in vitro.

Watermelon (Citrullus lanatus) and squash (Cucurbitae pepo) are traditionally grown in northern Serbia, province of Vojvodina. Most of the cucurbit cultivars grown in Serbia originate from imported seed. In July 2013, round, water-soaked lesions were observed on the fruits on sporadic squash plants grown in two fields of the breeder variety trials in Bački Petrovac. Affected tissue was light brown, slightly sunken, soft and macerated. From symptomatic plants (cv. GL Maxima), showing 30% of the symptom intensity, uniform population of bacterial colonies was isolated and one strain was chosen for the collection. In August of the following season, infection of the vine was observed on watermelon plants (cv. unknown) grown in a commercial field in Čelarevo. Soft rot brownish lesions developed on infected stems resulting in collapse and wilting of entire vines. The number of plants affected with the symptoms was less than 10%. Out of the colonies isolated from the diseased tissue, two bacterial strains were pu...

During 2017-2018, leaf and fruit spot and twig necrosis were observed in peach orchards located on Ćemovsko polje, near Podgorica, central Montenegro. The symptoms were observed on plants of differ...

In July 2020, symptoms of leaf and fruit spot were observed on two-year old apricot plants (Prunus armeniaca L.), cultivar Rubista in plantation covering approximately 0,5 ha near Podgorica, central Montenegro. The intensity of infection on leaves was more than 70%. Initially, leaf spots were mainly circular, 2 to 5 mm in diameter, water-soaked, surrounded by a weak chlorotic halo, but later became light to dark brown and necrotic. Eventually, the spots merged and necrotic tissue dropped out, leaving a "shot-hole" leaf appearance. On apricot fruits small, dark brown, mainly circular superficial lesions were observed. The lesions merged and formed large necrotic areas reducing the quality of fruits. Symptoms were not observed on woody parts, such as twigs or stem. A total of 10 bacterial strains, forming yellow, convex, and mucoid colonies on yeast extract-dextrose-CaCO3 (YDC) medium, were isolated from symptomatic leaf and fruit tissue. All strains induced hypersensitive reaction in tobacco leaves. They were Gram-negative, strictly aerobic, oxidase negative, catalase positive, hydrolyzed gelatine and esculin but not starch, and did not grow at 37°C, showing similar biochemical properties as a reference strain Xanthomonas arboricola pv. pruni (Xap) (NCPPB 416) used in all tests as a positive control. Strains were further identified by PCR analysis, using primer pair XapY17-F/XapY17-R (Pagani 2004; Pothier et al. 2011), resulting in a single band of 943 bp, characteristic for Xap. Additionally, BOX-PCR with the BOX A1R primer (Schaad et al. 2001) showed 100% homology in genetic profiles of all tested strains and control strain. Amplification and partial sequencing of the gyrB gene of four representative strains was performed using set of primers described by Parkinson et al. (2007). Obtained DNA sequences showed that analysed strains (GenBank nos. MW473770, MW473771, MW473772, and MW473773) share 99.44 to 99.57% of gyrB sequence identity with Xap pathotype strain ICMP51. Pathogenicity of all strains was confirmed by spraying young apricot shoots using a hand-held sprayer, and by infiltration of apricot leaves (cv. Roksana) from the abaxial surface using a syringe without needle, with the bacterial suspension (107 CFU/ml in sterile distilled water), in three replicates. Sterile distilled water and reference Xap strain (NCPPB 416), were used as negative and positive controls, respectively. The inoculated shoots and leaves were maintained at approx. 25°C and high humidity conditions. Tissue necrosis appeared on all inoculated shoots 5 to 11 days and leaves 5 to 9 days after inoculation. Koch's postulates were completed by re-isolation of the pathogen from inoculated tissue and identification by PCR using XapY17-F/XapY17-R primers. Based on pathogenic, biochemical and molecular characteristics, the strains isolated from apricot leaves and fruits in Montenegro were identified as Xap - causal agent of bacterial leaf spot and canker of stone fruits. This quarantine pathogen was previously reported on almond (Panić et al. 1998) and on peach (Popović et al. 2020) in Montenegro. This is the first report of Xap affecting apricot in this country. Therefore, strict phytosanitary measures have to be implemented to prevent spread of the pathogen in other areas and other susceptible hosts.