Blackleg outbreaks were noticed on three fields (about 100 ha total) in 2 consecutive years (2018, 2019) in one of the main potato growing areas in Serbia (Bačka region, Vojvodina). The percentage of infected plants reached 40 to 70%, with 10.5 to 44.7% yield reductions. From the three fields, out of 90 samples Pectobacterium carotovorum subsp. brasiliensis was most frequently identified and diagnosed as causal agent of potato blackleg in Serbia for the first time (29 isolates). Dickeya dianthicola was a less frequently causative bacterium, which was also noticed for the first time (nine isolates). A total of 38 isolates were characterized based on their phenotypic and genetic features, including a pathogenicity test on potato. The repetitive element PCR (rep-PCR) using BOX, REP, and ERIC primer pairs differentiated five genetic profiles among 38 tested isolates. Multilocus sequence analysis (MLSA) of four housekeeping genes, acnA, gapA, icdA, and mdh, revealed the presence of three so far unknown P. c. subsp. brasiliensis multilocus genotypes and confirmed clustering into two main genetic clades as determined in other studies. MLSA also revealed the presence of a new genotype of D. dianthicola in Serbia.

Potato blackleg is frequently observed on the production fields in the Bačka region of Vojvodina province, which is one of the largest potato-growing areas in Serbia. This disease usually occurs during June and July. In July 2020, blackleg symptoms in the form of stem necrotic lesions, vascular discoloration, hollow stems, and wilting of whole plants were noted on potato cultivar VR808 on a field 28 ha in size located in Maglić village (GPS coordinates 45.349325 N, 19.542768 E). Disease incidence was estimated at 20-25%. Isolations were performed from 12 potato samples on Crystal Violet Pectate medium (CVP). Stem sections consisted of brown lesions and healthy tissue (c.10 cm) were surface sterilized with ethyl alcohol 70% (w/v) and rinsed with sterile distilled water. Small pieces of tissue were taken at the edges of stem lesions (between healthy and diseased tissue) were soaked in phosphate buffer saline for 20 min and plated using a standard procedure (Klement et al. 1990). Single colonies that formed pits after 48 hours at 26 °C were re-streaked onto Nutrient Agar (NA) where creamy white colonies with smooth surfaces were formed. A total of 30 isolates were selected and DNA isolated from the colonies was further analyzed by polymerase chain reaction (PCR) using the partial dnaX gene (DNA polymerase subunit III gamma/tau) with primer pair dnaXf/dnaXr for Pectobacterium and Dickeya species identification (Slawiak et al. 2009). A single characteristic band of 535 bp was amplified in all isolates (Slawiak et al. 2009). DNA sequence alignment showed two distinct groups of isolates (Fig.S1), which were genetically uniform within each group. Using BLASTn search, it was established that the dnaX sequence of the first group (consisting of 19 Serbian potato isolates) had 99.79% identity with NCBI-deposited Pectobacterium versatile strains 14A and 3-2 from potato from Belarus (Acc. No. CP034276 and CP024842, respectively) as well as SCC1 from Finland (Acc. No. CP021894). The remaining 11 dnaX sequences had 100% identity with Pectobacterium carotovorum subsp. carotovorum strain CFBP7081 originating from water in Spain (Acc. No. MK516961). The partial dnaX sequences of three Serbian P. versatile isolates (Pv1320, Pv1520, and Pv1620) and one P. carotovorum subsp. carotovorum (Pcc2520) were deposited in GenBank under Acc. No. MW839571, MW805306, MW839572, and MW805307, respectively. These results, indicating combined infection in the observed field, signify the first identification of P. versatile in Serbia. Multilocus sequence analysis (MLSA) performed with proA (proAF1/ proAR1) and mdh (mdh2/mdh4) genes (Ma et al. 2007; Moleleki et al. 2013) grouped three tested Serbian potato P. versatile isolates together with P. versatile strains from NCBI (Fig.S2). For both tested genes, BLASTn search revealed 100% homology with P. versatile strain SCC1 from Finland. Three Serbian P. versatile potato isolates were deposited under Acc. Nos. MZ682623-25 for proA and MZ682620-22 for mdh genes. According to the routine tests suggested for Pectobacteriaceae (Schaad et al. 2001), Serbian isolates possessed microbiological traits identical to P. versatile description (Portier et al. 2019). Pathogenicity was performed on potato cultivar VR808 with three selected P. versatile isolates (Pv1320, Pv1520, and Pv1620) in the following assays: (i) surface-sterilized tuber slices with holes in the center filled with 100 µL of bacterial suspensions (adjusted to 109 CFU mL-1) to test the isolates' ability to cause soft rot, and (ii) young, four-week old plants with developed 3rd true leaf (c. 30 cm tall) were inoculated by injecting stems with bacterial suspension adjusted to 107 - 108 CFU mL-1 at a height 5 cm above the soil line. Negative controls were treated with sterile distilled water. Inoculated plants were kept under controlled conditions (25 °C temperature and >70% relative humidity). Each assay was replicated twice. Soft rot appeared on tuber slices 24 h after inoculation. On inoculated stems, initial symptoms manifested as greasy elongated spots at inoculation sites two days after inoculation (DAI), and subsequently extended along the vascular tissue and became necrotic. Whole plant's decay was recorded in five DAI, while negative controls remained healthy. To complete Koch's postulates, bacteria were re-isolated from symptomatic potato plants and confirmed by PCR and sequencing of dnaX. This first report of P. versatile in potato indicates that blackleg currently present in Serbia is caused by a diverse bacterial population. This pathogen was first identified in genome comparison as 'Candidatus Pectobacterium maceratum' (Shirshikov et al. 2018) and was later renamed as Pectobacterium versatile sp. nov. (Portier et al. 2019). Thus far, bacterium Pectobacterium carotovorum subsp. brasiliensis has been recognized as dominant pathogen on most of the infected fields in Vojvodina province, and was recently noted on one plot subjected to a combined infection with Dickeya dianthicola (Marković et al. 2021). Findings achieved in this study are highly relevant, as they point to the diversity in potato blackleg pathogens, likely due to the increasingly widespread distribution of imported seed potatoes.

In this paper, a comprehensive overview of the ‘Candidatus Liberibacter solanacearum’ presence in Europe was provided. The analyzed findings revealed that, since the first appearance of this pathogen in Finland and Spain in 2008, it has spread to 13 new European countries. Therefore, ‘Ca. L. solanacearum’ has spread very quickly across the European continent, as evident from the emergence of new host plants within the Apiaceae, Urticaceae, and Polygonaceae families, as well as new haplotypes of this pathogen. Thus far, 5 of the 15 ‘Ca. L. solanacearum’ haplotypes determined across the globe have been confirmed in Europe (haplotypes C, D, E, U, and H). Fully competent ‘Ca. L. solanacearum’ vectors include Bactericera cockerelli, Trioza apicalis, and B. trigonica; however, only T. apicalis and B. trigonica are presently established in Europe and are very important for plants from the Apiaceae family in particular. Moreover, psyllid species such as B. tremblayi, T. urticae, and T. anthrisci have also been confirmed positive for ‘Ca. L. solanacearum’. Constant monitoring of its spread in the field (in both symptomatic and asymptomatic plants), use of sensitive molecular diagnostic techniques, and application of timely management strategies are, therefore, of utmost importance for the control of this destructive pathogen.

The effects of plant growth promoting (PGP) bacteria on soybean growth and yield were tested in field conditions using four treatments: (A) Bradyrhizobium japonicum strain 526, combined with cell-free supernatants (CFS) of Bacillus sp. strain Q10 and Pseudomonas chlororaphis strain Q16; (B) B. japonicum 526 + Bacillus sp. Q10; (C) B. japonicum 526 + P. chlororaphis Q16 and (D) commercial fertilizer containing B. japonicum, which served as a control. The average values of dry weight per nodule and shoot dry weight had the maximum values in the B treatment. In dry shoots collected at the flowering stage, nitrogen and carbon content was similar across all treatments, while that of sulphur decreased in treatment A. Relative to the control (D), all treatments showed positive effects on pods number and grain mass per plant, with the best results yielded by treatment A. Nitrogen and sulphur content in grain were significantly higher in treatment C, whereas maximum carbon content was measured in treatment B. In the control, it was obtained the yield of 4,000 kgha^-1, which was in accordance with data reported by the seed producer for the same growing conditions (the maximum value). The yields of 4,229, as well as 4,286 and 4,400 kg ha^-1 were measured for variants C, B and A, respectively, which were statistically significant higher (5.73 to 10%) than the commercial fertilizer (D). The improvement in soybean growth and yield in the field trial achieved by addition of PGP strains Bacillus sp. Q10 and P. chlororaphis Q16 to B. japonicum 526 can result in more productive agricultural practices.

During May and June 2019, bacterial leaf spot were observed on peach (Prunus persica L. Batsch), in young plantation (2017, 2018) on four different cultivars, viz. Sugar Time, Britney Lane, Royal B...

The aim of this work was to identify and characterize the pectolytic bacteria responsible for the emergence of bacterial soft rot on two summer cabbage hybrids (Cheers F1 and Hippo F1) grown in the Futog locality (Bačka, Vojvodina), known for the five-century-long tradition of cabbage cultivation in Serbia. Symptoms manifesting as soft lesions on outer head leaves were observed during August 2021, while the inner tissues were macerated, featuring cream to black discoloration. As the affected tissue decomposed, it exuded a specific odor. Disease incidence ranged from 15% to 25%. A total of 67 isolates producing pits on crystal violet pectate (CVP) medium were characterized for their phenotypic and genotypic features. The pathogenicity was confirmed on cabbage heads. Findings yielded by the repetitive element palindromic-polymerase chain reaction (rep-PCR) technique confirmed interspecies diversity between cabbage isolates, as well as intraspecies genetic diversity within the P. carotovorum group of isolates. Based on multilocus sequence typing (MLST) using genes dnaX, mdh, icdA, and proA, five representative isolates were identified as Pectobacterium carotovorum (Cheers F1 and Hippo F1), while two were identified as Pectobacterium versatile (Hippo F1) and Pectobacterium odoriferum (Hippo F1), respectively, indicating the presence of diverse Pectobacterium species even in combined infection in the same field. Among the obtained isolates, P. carotovorum was the most prevalent species (62.69%), while P. versatile and P. odoriferum were less represented (contributing by 19.40% and 17.91%, respectively). Multilocus sequence analysis (MLSA) performed with concatenated sequences of four housekeeping genes (proA, dnaX, icdA, and mdh) and constructed a neighbor-joining phylogenetic tree enabled insight into the phylogenetic position of the Serbian cabbage Pectobacterium isolates. Bacterium P. odoriferum was found to be the most virulent species for cabbage, followed by P. versatile, while all three species had comparable virulence with respect to potato. The results obtained in this work provide a better understanding of the spreading routes and abundance of different Pectobacterium spp. in Serbia.