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Povzetek: In July 2024, a pooled leaf sample (D760/24) was collected from several plants of three watermelon cultivars (Citrullus lanatus cvs. Crimson Sweet, Asahi Miyako Hybrid F1 and Top Gun) grown in an open field (approx. 0.5ha) in Dombrava, Slovenia. The plants which were included in the pooled sample showed virus-like symptoms, such as leaf mosaic, wilting and necrosis (eXtra Supplementary material Fig. S1). The disease incidence was estimated at 10%. DNA and RNA were extracted following Mehle et al. (2013) and RNeasy Plant Mini Kit (Qiagen, Germany) protocols, respectively. The sample was tested positive by reverse-transcription (RT)-PCR for watermelon crinkle leaf-associated virus 1 (WCLaV-1) and WCLaV-2 ( Hernandez et al. 2021) and negative for other viruses (details on viruses tested and primers used are available in eXtra Table S1). The obtained amplicons of expected sizes of WCLaV-1 and WCLaV-2 movement protein (MP) and RNA-dependent RNA polymerase (RdRp) genes (eXtra Fig S2) were then subjected to Sanger sequencing (Eurofins Genomics, Germany) and BLAST analysis. The MP (PQ570004, PQ570006) and the RdRp (PQ570005, PQ570007) sequences exhibited 100% identity with multiple accessions of WCLaV-1, such as PP792977 and PP792976, and WCLaV-2, such as LC636073 and LC636074. Illumina high-throughput sequencing (HTS, Novogene, Germany, NovaSeq X Plus, PE150) identified WCLaV-1 (PV012703-04) and WCLaV-2 (PV012705-06) reads, along with cucumis melo amalgavirus 1 (CmAV1, PV012707) and solanum nigrum ilarvirus 1 reads (insufficient reads to reconstruct genome segments, it may originate from pollen contamination of nearby infected plants in the field (Rivarez et al. 2023)). HTS data were analyzed in CLC Genomics Workbench v. 24 (Qiagen, USA) using the pipeline by (Pecman et al. 2022). Consensus genome sequences were reconstructed by iterative read mapping to the most similar reference sequence of the virus obtained from NCBI GenBank. To check for WCLaVs in watermelon seeds sold in Slovenia, we tested five seed samples from Sugar Baby, Crimstar F1, and Crimson Sweet (three lots) by RT-PCR. We also tested four leaf samples from plants grown from these seeds at 3-5 true leaves stage. Both viruses were found in all seed and leaf extracts. However, mechanical inoculations with the sap of two samples (plants grown from infected seed sample and sample D760/24) on several commonly used indicator plants including Chenopodium quinoa, Capsicum annuum, Nicotiana clevelandii, Nicotiana glutinosa, Nicotiana benthamiana, Nicotiana tabacum cv. White Burley, Nicotiana rustica, Datura stramonium, Cucurbita pepo cv. Bianca di Trieste, and Cucurbita maxima did not result in their infection. Retrospective analyses of our HTS data of two watermelon and 84 other cucurbits samples from previous years showed WCLaV-1 and WCLaV-2 reads in two pooled samples (containing equal amount of RNA of each sample): one from 2018 and another from 2019. RT-PCR confirmed the presence of WCLaVs only in watermelons. The pool from 2018 was sequenced at GATC (Germany, NovaSeq 6000 S2, PE 150) and from 2019 in-house using Oxford Nanopore Technologies (UK, MinION Mk1B device, SQK-PCS108, R9 flow cell). All HTS reads are deposited in the NCBI Short Reads Archive (PRJNA1202089). This is the first report of WCLaV-1 and WCLaV-2 in Slovenia and Europe, the two viruses which were included to the Alert list of the European and Mediterranean Plant Protection Organization, due to limited knowledge about their epidemiology (EPPO 2023). Further research is necessary to determine the incidence of these viruses in Europe, elucidate their epidemiology, symptoms association and their potential impact on the production of watermelons in the region.
Ključne besede: WCLaV-1, WCLaV-2, watermelon, viruses, diagnostics
Objavljeno v DiRROS: 22.04.2025; Ogledov: 17; Prenosov: 2
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Povzetek: This study aimed to determine the effect of surface metallographic preparation (grinding, diamond polishing, and chemo-mechanical polishing using silica and hydrogen peroxide) on the surface roughness, morphology, chemical composition, and electrochemical behaviour of Ti-6Al-4V alloy. Roughness decreases from ca. 0.2 μm to 0.02 μm from grinding to polishing. A typical α+β microstructure can be observed only after chemo-mechanical polishing. The average composition of ca. 6 wt% Al, 4 wt% V, and rest Ti was determined regardless of the surface preparation. X-ray photoelectron spectroscopy revealed that the thickness of the oxide layer formed on chemo-mechanical polished samples is half that of ground samples. The metallographic preparation largely affects the corrosion behaviour of Ti-6Al-4V, which was investigated using electrochemical impedance spectroscopy and potentiodynamic polarisation in 0.9 wt% NaCl and artificial saliva at 37°C. At the open circuit potential, the chemo-mechanically polished Ti-6Al-4 samples showed superior corrosion resistance over ground samples. At potentials over 2.5 V vs Ag/AgCl, increased current densities were noted for chemo-mechanically polished samples, presumably related to the oxidation to a thicker oxide
Objavljeno v DiRROS: 18.04.2025; Ogledov: 81; Prenosov: 31
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Povzetek: Molybdate and vanadate ions were used as corrosion inhibitors for the clad aluminium alloy 2024-T3 in chloride solution to investigate the differences in their inhibitory effect. Electrochemical measurements in 0.1 M NaCl investigated the influence of inhibitor concentration from 0.5 mM to 250 mM, solution pH from 5 to 9 and immersion time at open circuit potential of up to 12 h. Both compounds act predominantly as anodic inhibitors; however, the effect of molybdate increases significantly at concentrations above 50 mM and leads to a broad passive range. Surface analysis of the samples exposed to inhibitor performed by X-ray photoelectron spectroscopy showed that the inhibitor layers consist of oxides of multiple valences. Scanning electron microscopy with chemical analysis was also used to characterise the inhibitor layers. Equilibrium diagrams of the aqueous species in the selected concentration range were generated to better understand the inhibition mechanism and to correlate the electrochemical data and data on surface properties.
Ključne besede: molybdate, corrosion inhibitors, aqueous chemistry
Objavljeno v DiRROS: 18.04.2025; Ogledov: 82; Prenosov: 23
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Povzetek: This study investigates the effects of fluoride and chloride ions on the corrosion of cold-rolled steel, aluminium alloy AA5754, and zinc, using ammonium bicarbonate as a buffer at pH 4 and compares electrochemical findings with thermodynamic calculations of E-pH diagrams. The distinct electrochemical behaviours of fluoride and chloride ions were confirmed, with fluoride-induced corrosion leading to the significant complex formation on cold-rolled steel and AA5754, the latter leading to a narrowing of the Al passive region. However, a comprehensive analysis of all ionic species in the solution (F−, Cl−, NH4+ and HCO3−) and their complex equilibria reveals that zinc's corrosion is primarily influenced by the overall ionic strength of the solution and further complexation with the buffering agent at higher pH levels, should these conditions occur during corrosion. In addition, this analysis also highlights the subtle differences in the stabilization effects of open circuit potential on cold-rolled steel and AA5754. The results underscore the importance of considering the overall solution equilibrium in thermodynamic analyses and provide a foundation for further research on the role of F- and Cl- ions in zirconium conversion coatings.
Ključne besede: bicarbonate, pitting, complexation
Objavljeno v DiRROS: 18.04.2025; Ogledov: 76; Prenosov: 23
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Povzetek: The Mediterranean endemic stony coral Cladocora caespitosa (Linnaeus, 1767) is the only reef-building and obligate zooxanthellate coral in the Mediterranean Sea. This endangered species is threatened by climate and anthropogenic impacts affecting the coastal zone of the Mediterranean Sea. Growth rates and colony state were monitored over 20 years on a C. caespitosa bank in the Marine Protected Area of Veliko Jezero in the Adriatic Sea (Mljet National Park, Croatia). The growth rate of corallites (from 2.02 mm to 5.32 mm annually) was similar to relevant studies in different areas of the Mediterranean Sea and showed a positive correlation with the average annual sea temperature. The coral colonies formed a highly aggregated bank and beds on rocky and sandy bottoms, from 6 to 18 m depth, within a semi-enclosed bay with high water exchange caused by tides. The marine area has experienced abnormally warm summers during the last two decades, with sea temperatures reaching up to 30°C driving population damage to the coral bank. Mortality events of C. caespitosa colonies caused by polyp bleaching and tissue necrosis, showed a positive correlation with high sea temperature anomalies during summer and autumn resulting in complete or partial mortality of the colonies. The excessive growth of macroalgal species on coral colonies seems to be a direct consequence of sewage discharges from nearby villages. The present climate-warming trend together with urbanization has severely and negatively affected the C. caespitosa coral bank in the Mljet National Park causing concerns for future viability.
Ključne besede: Adriatic Sea, coral bank, bioconstruction, ecological impacts, marine protected area
Objavljeno v DiRROS: 18.04.2025; Ogledov: 73; Prenosov: 22
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