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Povzetek: In March 2021, unusual plant stuning, collar, and wet root rot of lettuce (Lactuca sativa L.) during the rosette stage was observed in two commercial fields in Serbia (44°58'N, 20°32'E; 44°45'N, 20°43'E). Disease incidence in the fields (≈ 0.9 ha each) was approximately 15 and 20%, respectively. Initial above-ground symptoms were yellowing and wilting of leaves, while below-ground symptoms were collar, wet root rot, and lesions becoming necrotic. Eventually, whole plants wilted, collapsed, and died. A total of 35 symptomatic plants were collected from the fields, and diseased tissues were cut into small pieces, surface sterilized, and plated on potato dextrose agar (PDA). Isolation resulted in 20 morphologically uniform monoconidial isolates. The isolates formed white to creamy colonies, gradually becoming salmon pink, slimy, or moist in appearance, with sparse aerial mycelia. Numerous hyphal coils with conidiophores and hyaline, smooth-surfaced, ellipsoid to ovoid, septate or aseptate conidia were formed (4.5 to 10.1×1.2 to 3.7 μm (n = 100)). To confirm the species identity, the internal transcribed spacer (ITS) region and the D1/D2 region of a selected representative isolate 13-3-c were amplified and sequenced by using primer pairs ITS1/ITS4 (White et al. 1990) and N1/N2 (O’Donnell and Gray 1995), respectively. The sequences were deposited in GenBank (ITS: OR880564 and D1/D2: OR880567). Sequence analysis revealed 100% nucleotide identity with P. cucumerina isolates from different countries deposited in the NCBI GenBank, including isolate MH860704 (Vu et al. 2019) (ITS region) and isolate KY662256 (Su et al. 2017) (D1/D2 region). Neighbor-joining analysis was conducted based on the combined ITS and D1/D2 regions, and the tree was constructed with the substitution models (1,000 bootstrap). The combined phylogeny confirmed that the sequences shared a common clade with P. cucumerina. Hence, morphological, microscopic, and molecular characterization confirmed the pathogen as P. cucumerina (Palm et al., 1995; Carlucci et al., 2012). In a pathogenicity assay, 10 isolates were tested. Five 30-day-old lettuce plants (cv. Majska Kraljica) per isolate were root-dipped in the conidial suspensions (1×105 conidia/ml). The 10 inoculated plants were transplanted into 1 L pots containing sterile substrate (Floragard, Germany). Plants treated with sterile distilled water were used as controls. Plants were maintained in a greenhouse at 25 to 28°C under a 12-hour photoperiod (Cai et al., 2021). Four weeks after inoculation, stunting, chlorosis, and wilting of plants were observed, while collars and roots exhibited typical decaying symptoms. No symptoms were observed on the control plants. The pathogen was reisolated from symptomatic tissue as previously described. Koch's postulates were completed by confirming the identity of reisolates based on morphological features. To our knowledge, this is the first report of P. cucumerina on lettuce or any other crop in Serbia. P. cucumerina is already known as a pathogen of lettuce and other hosts grown in many countries worldwide, as well as in some European countries (Belgium, England, Italy, the Netherlands, and Switzerland) (Zhang et al. 2019). This emerging pathogen may cause significant economic losses in lettuce production in Serbia and in the entire Balkan region. Our results may help to develop effective management strategies based on accurate and timely identification and regular pathogen monitoring.
Ključne besede: detection, identification, salat, plant diseases
Objavljeno v DiRROS: 17.05.2024; Ogledov: 451; Prenosov: 183
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Povzetek: In temperate coastal environments, wide fluctuations of biotic and abiotic factors drive microbiome dynamics. To link recurrent ecological patterns with planktonic microbial communities, we analysed a monthly-sampled 3-year time series of 16S rRNA amplicon sequencing data, alongside environmental variables, collected at two stations in the northern Adriatic Sea. Time series multivariate analyses allowed us to identify three stable, mature communities (climaxes), whose recurrence was mainly driven by changes in photoperiod and temperature. Mixotrophs (e.g., Ca. Nitrosopumilus, SUP05 clade, and Marine Group II) thrived under oligotrophic, low-light conditions, whereas copiotrophs (e.g., NS4 and NS5 clades) bloomed at higher temperatures and substrate availability. The early spring climax was characterised by a more diverse set of amplicon sequence variants, including copiotrophs associated with phytoplankton-derived organic matter degradation, and photo-auto/heterotrophic organisms (e.g., Synechococcus sp., Roseobacter clade), whose rhythmicity was linked to photoperiod lengthening. Through the identification of recurrent climax assemblages, we begin to delineate a typology of ecosystem based on microbiome composition and functionality, allowing for the intercomparison of microbial assemblages among different biomes, a still underachieved goal in the omics era.
Ključne besede: marine microbial ecology, coastal seas, microbial community analyses, marine biology, marine ecology
Objavljeno v DiRROS: 17.05.2024; Ogledov: 667; Prenosov: 422
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Povzetek: Blooms of gelatinous zooplankton, an important source of protein-rich biomass in coastal waters, often collapse rapidly, releasing large amounts of labile detrital organic matter (OM) into the surrounding water. Although these blooms have the potential to cause major perturbations in the marine ecosystem, their effects on the microbial community and hence on the biogeochemical cycles have yet to be elucidated. We conducted microcosm experiments simulating the scenario experienced by coastal bacterial communities after the decay of a ctenophore (Mnemiopsis leidyi) bloom in the northern Adriatic Sea. Within 24 h, a rapid response of bacterial communities to the M. leidyi OM was observed, characterized by elevated bacterial biomass production and respiration rates. However, compared to our previous microcosm study of jellyfish (Aurelia aurita s.l.), M. leidyi OM degradation was characterized by significantly lower bacterial growth efficiency, meaning that the carbon stored in the OM was mostly respired. Combined metagenomic and metaproteomic analysis indicated that the degradation activity was mainly performed by Pseudoalteromonas, producing a large amount of proteolytic extracellular enzymes and exhibiting high metabolic activity. Interestingly, the reconstructed metagenome-assembled genome (MAG) of Pseudoalteromonas phenolica was almost identical (average nucleotide identity >99%) to the MAG previously reconstructed in our A. aurita microcosm study, despite the fundamental genetic and biochemical differences of the two gelatinous zooplankton species. Taken together, our data suggest that blooms of different gelatinous zooplankton are likely triggering a consistent response from natural bacterial communities, with specific bacterial lineages driving the remineralization of the gelatinous OM.
Ključne besede: jellyfish, proteases, bacterioplankton, ocean biogeochemistry
Objavljeno v DiRROS: 16.05.2024; Ogledov: 499; Prenosov: 375
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Povzetek: Aim: The Anthropocene is characterised by urban and agricultural landscapes. Within these landscapes, natural to semi-natural habitats are fragmented, isolated and disturbed to varying degrees. Species associated with these natural habitats have to content with the surrounding landscape, both in terms of level of isolation, and matrix type and quality. We investigated the community structure, trait distribution and individual traits of carabid beetles in boreal forest fragments within three matrices: urban, agricultural and freshwater lake. Location: City of Lahti and its surroundings, southern Finland. Taxon: Coleoptera, Carabidae. Methods: Using pitfall traps from June to October 2019, we collected carabid beetles from eight spruce-dominated forest fragments in the urban matrix, 10 fragments in an agricultural matrix, seven fragments on lake islands and three large control forests at the outskirts of the city. Results: Compared to natural forests, carabid beetles in forest fragments in these matrices showed distinct assemblages, and with beetle diversity the highest in fragments in the agricultural landscape. Fragments in the urban and lake island landscapes were characterised by small-sized species, and those capable of flight. We also found strong intraspecific trait responses in terms of body size, with some generalist species being significantly smaller in urban, agricultural or lake island fragments compared to the controls. Main Conclusions: The matrix has a clear effect on carabid beetle communities, both in terms of taxonomic and trait distribution, and filters for communities of smaller sized species and those capable of flight. Such overall community and intraspecific effects can have considerable effects on populations and community assemblages: As anthropogenic effects intensify in urban and agricultural landscapes, our findings may be the expression of further morphological and physiological responses, and eventually in the adaptation of those species that can cope with the Anthropocene.
Ključne besede: biogeography, ground beetle, urban lake, agricultural lake, freshwater lake, zoology
Objavljeno v DiRROS: 16.05.2024; Ogledov: 499; Prenosov: 509
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Ključne besede: rak, onkologija, nacionalni programi, državni program obvladovanja raka (DPOR), umetna inteligenca, imunoterapija, zborniki
Objavljeno v DiRROS: 16.05.2024; Ogledov: 543; Prenosov: 526
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