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Good photosynthetic features and a favorable water regimes of woody plants improve their survival and remediation potential under unfavorable ecological conditions. Accordingly, we here present results of testing plant tolerance of Pb, Cd, Ni, and diesel fuel based on gas exchange parameters and WUE of four poplar and two willow clones grown in a greenhouse on soil culture. Photosynthesis and transpiration of plants grown on soils with individually applied heavy metals decreased significantly, but this was less obvious in the case of Cd treatment. A heavy metal mixture in the soil induced significant reduction in photosynthesis (by more than 50%). Diesel fuel as the only pollutant in soil caused very strong and significant inhibition of photosynthesis and transpiration of willow clones. The results indicate genotypic specificity of all investigated physiological parameters and mark poplar clones as very useful in phytoextraction technology for the bio-cleaning of chemically polluted soils.

Samples of various host plants from different locations in Serbia showing foliar symptoms resembling those caused by the cucumber mosaic virus (CMV) were collected. Samples were considered CMV-infected after detection by double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA). Fifteen CMV isolates were selected for developing a reverse transcription-polymerase chain reaction (RT-PCR) restriction fragment length polymorphism (RFLP) protocol and a more detailed molecular characterization of all five genes. Based on in silico RFLP, the following restriction enzymes were selected: HindIII, SacII (1a gene), MluI (2a gene), StuI, SalI (2b gene), BaeI (movement protein (MP) gene of CMV), SfcI, and HaeIII (capsid protein (CP) gene), which were capable of distinguishing between subgroups of CMV based on the obtained characteristic restriction patterns. According to in situ RFLP, the predominant haplotype IA; IA, IA; IA, IA was determined in 14, while the distinct haplotype II; II, II; II, II was found in only one isolate. Sequence analyses of two selected Serbian CMV isolates with different restriction patterns and haplotype profiles confirmed the RFLP results, showing that isolates 674-11 and 137-13 belong to subgroups IA and II, respectively. Different restriction patterns after digestion of all five CMV genomic regions proved to be a simple way to investigate the natural population of CMV. This study provides insight into the genetic structure of the CMV population in Serbia.

Certified and non-certified seed of the soybean cultivar Dukat showing symptoms of mottling were collected at the preharvest stage from soybean fields in the location Tamiš (South Banat District, Serbia) in 2021. To identify the presence of soybean mosaic virus (SMV), a total of 10 samples, five of each type of seed, were selected and tested by RT-PCR using primers SMVCPF/SMVCPR, which amplify a fragment of the coat protein (CP) gene. The molecular assay confirmed the presence of SMV in all tested seed samples. For further analyses, the CP and P1 genome regions of two selected isolates (DS-21 and NDS-21, representing certified and noncertified seed, respectively) were partially sequenced. The Serbian SMV isolates shared very low nucleotide diversity and were mutually closely related based on the CP (99.8% nt/99.2% aa identities) and P1 (99.7% nt/ 99.6% aa identities) regions. Phylogenetic analyses based on both genomic regions showed that the two Serbian SMV isolates originating from certified and noncertified seed belonged to one cluster, and consequently to the same SMV subpopulation. Since this is the first molecular characterization of SMV in Serbia, further research should be focused on collecting samples from different locations and of different varieties, and on determining the variability of SMV population in Serbia based on whole-genome analysis. This research will contribute to better understanding of the epidemiology of this pathogen with the ultimate goal of developing and implementing appropriate control measures.

Urban vegetation affects the environment in several ways. It improves air quality, the height of drainage water, and soil properties, balances temperature variations (temperatures are lower in summer and higher in winter in the presence of urban vegetation), reduces UV radiation, reduces noise, increases relative air humidity and contributes to certain types of social development (ecological, aesthetic, economic aspects of urban development). Urban vegetation especially improves microclimatic conditions in large cities and considerably contributes to the urban increase of oxygen. It is of vital interest to pay attention to its size and quantity in urban areas. To assess CO2 absorption and O2 release, the photosynthesis of five tree species and three types of herbaceous plants species was measured. The obtained results show that there is a certain variability in terms of the species that was analyzed. Thus, fast-growing woody deciduous species are more suitable due to the greater and faster growth of biomass, which requires a larger amount of CO2 compared to herbaceous species. The careful calculation indicates the requirement of two to four trees per person or 30-40 m2 of a grassy area per person to balance the inhabitant oxygen consumption. For the overall contribution of green vegetation, the multiple qualitative benefits of green areas in urban areas should certainly be considered.

Background: In modern business conditions, intangible assets have a dominant impact on the business performance of the company. R&D activities, the level of R&D investments and the efficiency of R&D investments affect company profitability. There are various performance indicators of R&D activities that have an impact on profitability. Purpose: Bearing in mind that R&D is the precondition of growth and development of the company, as well as the efficiency of R&D investments, is the key determinant of economic corporate responsibility, the purpose of this paper is to investigate the effects of various performance indicators of R&D activities on companies' profitability. The aim of this paper is to investigate the effects of R&D investments, R&D intensity and return on R&D capital on the profitability of highly innovative companies. Study design/methodology/approach: Correlation, regression and cluster analyses were performed to provide an empirical investigation of the impact of key R&D performance indicators on the return on assets (ROA) of highly innovative companies, which are on the list of the top R&D spenders in the world. The data for the analysis comprises 24 R&D-intensive companies for the period 2013-2021. Findings/conclusions: The regression analysis results conducted on the determined clusters show that all three analyzed indicators of R&D activities have a positive and statistically significant impact on ROA in highly R&D-intensive companies. It is confirmed that the effects of various indicators of R&D activities are bigger in companies with higher RDII. Limitations/future research: The sample encompasses the 24 companies listed among the top 50 R&D spenders worldwide, which is considered insufficient for extensive analysis. The other limitation is related to the short research period. As the R&D activities produce yields after several years, the possible direction for future research is to investigate the impact of accumulated R&D investment over several years on ROA.

Human resources are one of the driving forces and main determinants of agricultural competitiveness, contributing to its improvement through properly formed and constantly renewed knowledge and skill enhancement of agricultural workers. In the context of scarce natural resources, demographic changes, need for more intensive agricultural production based on modern technology, human resource development in agriculture becomes imperative. The aim of the research is to assess the human resources in agriculture of Serbia through the prism of data available in the Statistical Office of the Republic of Serbia and World Bank. The research results show fluctuations in the rural population and employees in agriculture in the analysed period, confirming their negative trend and predicting further decrease based on the forecast method. In order to overcome limitations related to the number and qualifications of agricultural employees, the special focus has been given to the formal and informal education of workers in agriculture, ensuring their capability to respond to market needs and future challenges.

In November 2019, virus-like symptoms resembling those caused by turnip yellows virus (TuYV) were observed in many canola crops across Serbia. In order to identify their causal agent, a total of 206 samples were collected and analyzed for the presence of TuYV, cauliflower mosaic virus (CaMV) and turnip mosaic virus (TuMV), using commercial double-antibody sandwich (DAS)-ELISA kits. TuYV was detected serologically in 91.75% of tested samples collected at 24 locations in all of seven inspected districts. None of the samples tested positive for TuMV and CaMV. Further molecular characterization based on the partial P0 gene sequences of seven selected ELISA-positive samples showed that Serbian TuYV isolates collected in 2019 shared low nucleotide diversity, and that they were closely related to previously identified Serbian cabbage and mustard isolates of TuYV. Phylogenetic analysis showed that TuYV isolates from Serbia were clustered within the TuYV/BrYV group. Moreover, nucleotide and amino acid sequence comparison of all TuYV isolates originating from Serbia, supported with a phylogenetic tree, indicated the existence of two virus subpopulations in Serbia. Further research should focus on determining the variability of TuYV population in Serbia, based on a whole-genome analysis that will contribute to a better understanding of the epidemiology of this pathogen, aiming at developing and implementing appropriate control measures.

The research aims to determine the intensity and direction of the impact of the global health and economic crisis from 2020 on the export competitiveness of the agri-food sector of the Republic of Serbia. Empirical study shows that there was an increase in the importance of exports of agri-food products in the crisis year 2020 according to all analysed indicators (net exports index, index of contribution to trade balance, relative coverage of imports by exports, unit values of exports). This confirms the hypothesis that this sector has exceptional resilience to crisis events. Moreover, net exports of these products increased significantly in 2020 compared to 2019 as a pre-crisis year. Therefore, the agri-food sector of the Republic of Serbia plays an important role in periods of such a crisis caused by non-economic factors, because it can compensate for the decline in exports and gross value added of other sectors.

The utilization of ash obtained as a result of the combustion of fossil fuels (coal, peat) or biomass (straw, wood, solid waste) is an environmental problem that should be optimally solved. The chemical characteristics of ash depend on several factors, mostly on sources of fuel. According to characteristics, ash can be used in agriculture, forestry, or utilized for other purposes. The content of heavy metals (Cd, Ni, Pb, Cr) in peat ash is several times higher than in willow wood ash and straw ash. It means that peat ash application is limited to agricultural crops and its optimal application is one year before planting SRC trees, especially on poor and acid soils. The application of peat ash at a dose of 10 mg dry mass ha-1 in willow plantations on post-mining peaty soils changed soil acidity from 5.2 pH to 5.88 pH and stimulated tree growth. Wood and straw ash was applied to wil­low plantations on arable loam-sandy soils in doses 0.5, 1.0, and 1.5 t dry mass ha-1. The positive effect of ash application in doses 1.0 and 1.5 t dry mass ha-1 showed in the second year after the application both for soil and for willow growth.

The goal of this research is an assessment of the possible use of peatlands biomass and straw for the production of mixed bio-pellets. Peaty soils are a specific type of soils formed as the result of wetlands drainage. Peat mining is completed by the factory if the layer of the peat is less than 1-2 meters and not enough deep for effective mechanical excavation. After the peat excavation is finished, the biggest problem is the use of these lands for other purposes. One of the perspective directions is rewetting of post-mining peatlands to stimulate the growth of common reed, cattail, fescue, sedge, and other grasses which may grow in natural conditions, and also improve conditions for the cultivation of other plants, including trees. The yield of wetland grass in Belarus varies from 8.1 to 14 DM g ha-1 per year. The yield of willow wood can reach 8-10 of DM g ha-1 per year. The highest prime cost of biomass is obtained for willow wood, but it will be lower with the enlargement of the plantation area. Pellets with a high content of wood residues (sawdust) have the best technological parameters including calorific value when compared to pellets from only peat and peat plus straw. Biomass production on degraded peaty soils has also an ecological effect. The cost of carbon quotas on the market varies from 20 to 25 euro per ton, and biomass production can provide additional profit in the case of CO2 emissions trading depending on the biomass content in the fuel.

Honeycomb sandwich structures, composed of many regularly arranged hexagonal cores and two skins, show excellent impact performance due to strong energy absorption capability under impact loads. In this paper, a numerical study of low velocity impact on honeycomb sandwich panels filled with circular tubes in the in-plane direction was performed. To calibrate the numerical model, simulation results in the out-of-plane direction are compared with the experimental ones. The numerical modelling of the drop weight test was carried out using the nonlinear explicit finite element code Abaqus/Explicit. The impact responses are presented as the contact force between the impactor and the panel versus the time. It was concluded that the filled honeycomb panel absorbs the same amount of impact energy in a shorter time than an empty one. In addition, the deflections of the front and back face-sheets are investigated. The panel degradation and the stress distribution during the crushing are also discussed.

In the present study, a numerical investigation of three-point bending test of the open-hole damaged sandwich structures with Nomex TM honeycomb core and aluminium alloy skins is carried out. In order to evaluate the degradation of the mechanical properties of these damaged structures, a finite element model is realized and tested using Abaqus/Explicit. To validate the accuracy of the numerical model, the obtained numerical results of the intact panels are calibrated with the experimental results. The load-displacement curves of the damaged structures showed a significant decrease of the peak force and the flexural elastic modulus compared to the intact ones. The study indicated that the degradation level of these mechanical parameters is in a direct relationship with the damage size. In addition, the energy absorption of the damaged panels is calculated and compared to the intact one.