Goran Barać

The aim of this study was to identify and characterize the bacterial pathogen causing leaf spot of spinach using phenotypic and molecular analysis. Isolation on NSA resulted in the formation of numerous morphologically uniform Pseudomonas-like colonies, from which 12 representative isolates were selected for further identification. All isolates caused disease symptoms on spinach plants and leaves inoculated under controlled conditions. The LOPAT test results indicated that the spinach isolates could not be assigned to any of the previously described groups of fluorescent Pseudomonas. Based on multi-locus sequence analysis (MLSA) of the gltA, gapA, gyrB, and rpoD genes, the spinach isolates were assigned to distinct phylogenetic lineages within the broad Pseudomonas fluorescens species complex. Nine isolates (SP12, SP21, SP22, SP31, SP32, SP33, SP34, SPR1, SPR4) formed a core clade (Group I) clustering with unclassified Pseudomonas sp. reference strains, while SP14 and SP24 formed well-supported basal branches leading to this group. Isolate SPR3 represented an early-diverging lineage branching between the P. marginalis reference group and the remaining spinach isolates. These findings provide the first characterization of Pseudomonas strains associated with leaf spot of spinach in Serbia and demonstrate diversity within the P. fluorescens species complex on this host, though whole-genome sequencing will be required for definitive species-level identification. Host range assessment revealed significant differences in AUDPC values among the tested host types (Holm-adjusted p < 0.01). Beet exhibited the highest disease intensity, followed by sugar beet, whereas Swiss chard showed the lowest disease intensity under the experimental conditions. These findings demonstrate the considerable diversity of the Pseudomonas population associated with spinach and represent the first report of spinach-associated strains belonging to the P. fluorescens species complex in Serbia (Vojvodina), where such investigations have not previously been conducted or reported.

Quince (Cydonia oblonga Mill.) is a well-known pome fruit species, primarily used for the production of jams and marmalades as well as for pear rootstocks. It has long been cultivated in Serbia at various locations and it possesses vast genetic variability. The aim of this study was to evaluate genetic diversity of 36 genotypes collected from the Fruška Gora locality. Seven SSR markers were used for genetic diversity analyses, revealing a total of 85.7 % polymorphic loci. Six of them were polymorphic, while marker Hi02d04 was homozygous. A total of 20 alleles were recorded, with an average number of alleles per marker of Na = 1.58. The number of effective alleles was Ne = 1.4, observed heterozygosity was Ho = 0.34, while expected heterozygosity was He = 0.22. Principle coordinates analyses (PCoA) explained 74.60% of total diversity with its 3 coordinates and formed 4 different groups of genotypes. The dendrogram constructed with the UPGMA method placed genotypes in 3 different clusters, with variation observed within clusters. The use of SSR markers revealed significant differences between the tested genotypes, providing a closer insight into the state of the genetic resources of this pome species in our country.

Sweet cherry (Prunus avium L.) is an economically important fruit species with considerable genetic variability, particularly among autochthonous cultivars. This study aimed to evaluate the genetic diversity and population structure of six indigenous sweet cherry cultivars from the Ohrid region in North Macedonia using whole-genome resequencing. A total of approximately 2.27 million single-nucleotide polymorphisms (SNPs) and 263 thousand insertions and deletions (InDels) were identified, indicating high genomic variability. Population structure and phylogenetic analyses revealed two distinct genetic clusters among the studied cultivars. The Ohridska bela cultivar showed the highest level of genetic differentiation, highlighting its importance as a valuable genetic resource. Functional annotation of genetic variants demonstrated significant variability in genes associated with flowering time, dormancy, and stress response, suggesting adaptation to local environmental conditions, while genes related to fruit ripening were highly conserved. Additionally, the rapid linkage disequilibrium decay confirmed the high genetic diversity within the population. These findings emphasize the importance of Macedonian autochthonous sweet cherry germplasm for breeding programs, conservation efforts, and future adaptation to changing environmental conditions.

Cherry stalks, as primary by-products of sour cherry (Prunus cerasus L.) and sweet cherry (Prunus avium L.) harvesting, are often considered agricultural and industrial waste. However, cherry stalks are recognized in traditional and ethno medicine for their therapeutic properties, due to their high content of natural antioxidants. In this study, the concentrations of total phenolic and total flavonoid compounds, as well as antioxidant activity, were evaluated in different cherry stalk extracts (aqueous, methanol, ethanol, and acetone) obtained from sweet cherry cultivars, sour cherry cultivars, and a wild cherry sample. The results depended on the cultivar and the solvent used for extraction. The highest concentrations of total phenolic and total flavonoid compounds were observed in acetone extracts. In various antioxidant tests, the antioxidant activity varied depending on the genotype.

In August 2020, the unusual appearance of crown gall symptoms was observed on the tobacco plants (hybrid PVH2310) grown in fields in the Golubinci (Srem district, Serbia) locality. The causal agent isolated from galls located on tobacco roots formed circular, convex, and glistening light blue colonies, and then dark to olive-green-colored bacterial colonies on a semi-selective D1 medium. Molecular analysis based on multiplex PCR and multi-locus sequence analysis (MLSA) using concatenated sequences of the atpD, dnaK, glnA, and rpoB genes as well as 16S rRNA identified Serbian tobacco isolates such as Agrobacterium tumefaciens (biovar 1). Two duplex PCR methods confirmed the presence of the virD2 and virC genes in tobacco isolates. Pathogenicity tests performed on carrot discs and squash fruits resulted in tumor/gall formation after 12 to 16 days post inoculation, respectively. Pathogenicity was also confirmed on tobacco plants, where isolates caused tumor development 21−25 days after inoculation. API 50 CH generated results regarding the biochemical features of the Serbian tobacco isolates. As A. tumefaciens (biovar 1) as a cause of tobacco crown gall has previously been documented solely in Japan, there is presently no data on its wider occurrence. Therefore, this first detailed investigation of A. tumefaciens isolated from naturally infected tobacco in Serbia will contribute to a better understanding of it at the global level.

Altogether, 39 cereal flour samples taken from a Serbian market were analyzed for mycobiota and mycotoxin content, among which were six Triticum aestivum specimens, five Triticum dicoccum specimens, four Hordeum vulgare specimens, five Fagopyrum esculentum specimens, three Secale cereale specimens, five Triticum spelta specimens, four Avena sativa specimens, two Oryza sativa specimens, two Zea mays specimens, and one specimen each of Panicum miliaceum, Triticum monococcum, and Triticum turgidum ssp. turanicum. To determine the mycobiota content using dilution techniques, the flour samples were transferred to a non-selective DG18 nutrient. The number of coloniforming units (CFU/g) varied from less than 100 (in the case of five samples, namely, two O. sativa, and one specimen each of S. cereale, H. vulgare, and T. aestivum) to as high as 5000 CFU/g (S. cereale), 6000 (A. sativa), 11,000 (T. aesticum), and 40,000 (Z. mays). The identification of fungal genera and species was performed on Czapex-Dox Agar and Potato dextrose Agar on the basis of the isolates’ colony characteristics and the morphology of the examined reproductive organs. The isolated fungi belonged to the following genera: Aspergillus, Penicillium, Alternaria, and Fusarium. Species from these genera are well-known mycotoxin-producing fungi. Among the identified species were A. candidus, A. flavus, A. carbonarius, A. ochraceus, A. oryzae, P. solitum, P. citrinum, P. griseofulvum, P. brevicompactum, A. alternata, F. avenaceum, and F. graminearum. The mycotoxin content was determined via the ELISA technique using Eurofins Technologies Hungary KFT kits for aflatoxin B1, deoxynivalenol, total aflatoxins, ochratoxin A, and zearalenone. In the case of eighteen samples, the total aflatoxin content was above the limit of detection, and seven of these samples were contaminated with aflatoxin B1, eight were contaminated with ochratoxin A, two were contaminated with dexynivalenol, and one was contaminated with zearalenon. Two samples of T. aestivum were contaminated with one or more toxins (33%), and the number of samples contaminated three for T. dicoccum (60%), one for H. vulgare (25%), four for F. esculentum (80%), one for S. cereale (33%), two for T. spelta (40%), three for A. sativa (75%), two for O. sativa (100%), two for Z. mays (100%), one for P. miliaceum (100%), one for T. monococcum (100%), and one for T. turgidum ssp. turanicum (100%).

The present study focused on detecting bacteria of the Xanthomonas spp. complex (X. euvesicatoria, X. vesicatoria, X. perforans and X. gardneri) and examining their influence on certain quality parameters of pepper seed collected from the territory of Smederevska Palanka (Serbia). The analysis included 27 non-commercial pepper seed genotypes (including chili and sweet pepper) collected in 2021. Several parameters of the quality of analyzed pepper seed (germination energy, total germination, moisture and seed health) were determined. The results showed that out of a total of 27 analyzed samples of pepper seed, the presence of X. euvesicatoria was detected in 13 of them. The presence of X. vesicatoria, X. gardneri and X. perforans was not confirmed. Germination energy of infected seed was 52-84%, and of bacteria-free seed 63-90%; total germination of infected seed was 66-91%, and of bacteria-free seed 80-95%. Seed moisture of infected seed samples was 6.1-12%, and of bacteria-free seed 6.2-8.1%. These parameters did not show significant statistical difference (p>0.05). The presence of seed-borne fungi Fusarium sp. accounted for up to 3% in 25 samples, while it was up to 6% in the remaining two; Alternaria sp. ranked from 1-4% in 25 samples, and up to 5% in only two samples. The results led to a conclusion that the bacterium X. euvesicatoria is the predominant pathogen of the Xanthomonas spp. complex, but it did not affect the quality parameters of the tested pepper seed.

An overview of Serbian autochthonous genotype selection in Prunus genus Preuzmite PDF Autori: Nebojša Milošević Ivana Glišić Sanja Radičević Slađana Marić Milena Đorđević Tomo Milošević Vera Rakonjac Goran Barać Naziv časopisa: Voćarstvo = Journal of Pomology Godina: 2022 Tom: 56 Broj: 213-214 Strane: 69-77 Jezik: English DOI: 10.65845/pomology.2022.56.213_214.1 Rezime: Fruit species of the Prunus genus...

Severe climate alterations that seriously challenge fruit production, combined with the demand for healthy, pesticide-free fruits, continuously direct rootstock/cultivar selection towards high adaptable varieties breeding. This study aimed to investigate the rootstocks’ influence on the performance of grafted ‘Summit’ cherry trees, including potentially dwarfing Prunus cerasus , Prunus fruticosa and Prunus mahaleb rootstock candidates. Anatomical properties of rootstock and scion stems were investigated to determine variation among different rootstocks and scion-rootstock combinations and to establish the link between trunk hydraulic conductivity, effective tree crown volume and yielding potential. Cross-section anatomical characteristics varied significantly both in rootstock and scion stems, indicating a clear influence of rootstock genotype on grafted sweet cherry trees. It was observed that all investigated cherry rootstock candidates belong to the low-vigorous rootstocks, based on the estimated effective crown volume of grafted trees compared to ‘Gisela 5’, with values ranging from 0.86 to 2.97 m ³ in the fifth year after planting. Results showed a statistically significant positive correlation between trunk hydraulic conductivity, effective tree crown volume and yielding potential, with correlation coefficients up to 0.96. Significantly higher effective crown volume and trunk hydraulic conductance of trees grafted on P. cerasus compared to the trees on control, as well as highest yielding potential, showed better adaptation of these rootstock candidates in the trial without irrigation implemented. It was found that PC_05_04 rootstock candidate could be considered as the most appropriate choice when raising the high-density sweet cherry plantations, due to assessed parameters of vegetative and generative growth.

The present study was conducted on 106 leaf samples of Prunus species (44 plum, 47 myrobalan plum, 10 apricot, 3 peach, 1 blackthorn, and 1 sour cherry) collected from the Vojvodina province of Serbia and assessed for the presence of Plum pox virus (PPV) with the aim of establishing whether trees growing along roadsides and in backyards could be sources of PPV infection in commercial orchards. Analyses confirmed PPV infection in 68.2%, 38.6%, and 20% of plum, myrobalan plum and apricot samples, respectively. The infection level varied considerably across locations, with 80% noted in Uljma, followed by 69% in Sremska Kamenica, 60% in Becej, 50% in Temerin, 50% in Senta, 40% in Petrovaradin, 31% in Novi Sad, 30% in Susek, and 20% in Subotica. As no difference in infection rates was noted between young and older plum trees, the infections seemed to have occurred in their early life stage. Trees growing along roadsides were infected to a higher extent (89.6%) than those in backyards (66.6%). In some cases, symptomless trees were also proven to be PPV positive, indicating that they are a potentially important source of further virus infections. Due to the widespread presence of the virus, tolerant or hypersensitive cultivars are recommended for planting new orchards.