Mercury in Macrolepiota procera (Scop.) Singer and Its Underlying Substrate—Environmental and Health Risks Assessment

Wild-growing edible mushrooms are valuable food with a high content of proteins, fibers, antioxidants, and they are characterized by their specific taste and flavor. However, from an ecotoxicological point of view, they are a risk commodity because of their extremely high bioaccumulative capacity to accumulate the risk elements and contaminants from the environment. In the present study, we examined mercury (Hg) contamination in 230 fruiting bodies of Macrolepiota procera (Scop.) Singer and 230 soil/substrate samples, which were collected in foraging seasons 2015–2019 from 22 different locations in Slovakia. Total mercury content was determined by cold-vapor AAS analyzer AMA 254. The level of contamination and environmental risks were assessed by contamination factor (Cf), index of geoaccumulation (Igeo), and potential environmental risk index (PER). Bioaccumulation factor (BAF) was calculated for individual anatomical parts of M. procera. Mercury content in the soil/substrate samples varied between 0.02 and 0.89 mg kg−1 DW, and in mushroom samples between 0.03 and 2.83 mg kg−1 DW (stems), and between 0.04 and 6.29 mg kg−1 DW (caps). The obtained results were compared with the provisional tolerable weekly intake for Hg defined by WHO to determine a health risk resulting from regular and long-term consumption of M. procera.

Bearing Capacity and Geotechnical Properties of a Sandy Soil Substrate Contaminated with Oil Derivatives (Diesel fuel and Kerosene)

This research investigated the bearing capacity and geotechnical properties of a sandy soil substrate contaminated with oil derivatives, diesel fuel, and kerosene. For this purpose, a site with a clayey sandy soil substrate was considered to evaluate the effects of contamination on the geotechnical properties and bearing capacity of the substrate in both clean and contaminated states. Then, the substrate of the site was artificially contaminated with diesel fuel and kerosene and underwent field and laboratory tests. The experiments, including the Atterberg limits, standard proctor compaction, uniaxial compressive strength, strength, and freeze-thaw durability tests, were performed on prepared samples. Also, to determine the bearing capacity of the contaminated and intact substrates, a plate load test was conducted at the site. The results indicate that contamination by oil derivatives reduces the strength and increases the settlement and displacement of the contaminated substrate, where the effects of diesel fuel are more significant than those of kerosene. The results of this research are compared to previous studies. The literature shows that most research in this area was carried out in the laboratory, and there is a lack of in-situ studies. This study showed that the presence of oil contaminations caused a 3.5% reduction in the amount of soil Atterberg limits. The contaminations also reduced the dry density and uniaxial compressive strength of the soil by 2.5% and 20%, respectively. The results presented were consistent with the results of other researchers. However, some studies have suggested an increase in the Atterberg limits due to oil contaminants in the soil.

Role of biochar, compost and plant growth promoting rhizobacteria in the management of tomato early blight disease

The individual role of biochar, compost and PGPR has been widely studied in increasing the productivity of plants by inducing resistance against phyto-pathogens. However, the knowledge on combined effect of biochar and PGPR on plant health and management of foliar pathogens is still at juvenile stage. The effect of green waste biochar (GWB) and wood biochar (WB), together with compost (Comp) and plant growth promoting rhizobacteria (PGPR; Bacillus subtilis) was examined on tomato (Solanum lycopersicum L.) physiology and Alternaria solani development both in vivo and in vitro. Tomato plants were raised in potting mixture modified with only compost (Comp) at application rate of 20% (v/v), and along with WB and GWB at application rate of 3 and 6% (v/v), each separately, in combination with or without B. subtilis. In comparison with WB amended soil substrate, percentage disease index was significantly reduced in GWB amended treatments (Comp + 6%GWB and Comp + 3%GWB; 48.21 and 35.6%, respectively). Whereas, in the presence of B. subtilis disease suppression was also maximum (up to 80%) in the substrate containing GWB. Tomato plant growth and physiological parameters were significantly higher in treatment containing GWB (6%) alone as well as in combination with PGPR. Alternaria solani mycelial growth inhibition was less than 50% in comp, WB and GWB amended growth media, whereas B. subtilis induced maximum inhibition (55.75%). Conclusively, the variable impact of WB, GWB and subsequently their concentrations in the soil substrate was evident on early blight development and plant physiology. To our knowledge, this is the first report implying biochar in synergism with PGPR to hinder the early blight development in tomatoes.

Phosphorus forms in technosols afforested with N-fixing and non-N-fixing tree species

<p>Tree species capable of forming a symbiosis with N-fixing bacteria may affect P availability in reclaimed technosols. The objective of this study was to compare the effect of N-fixing tree species and non-N-fixing species on phosphorus forms in technosols developing from various materials. Soil samples were taken under black locust (Robinia pseudoaccaccia), black alder (Alnus glutinosa), silver birch (Betula pendula) and Scots pine (Pinus sylvestris) from two depths (0-5 cm and 5 – 20 cm). The soil substrates were fly ashes, sands and clays. In the soil samples measured were concentrations of total P (P<sub>t</sub>),  water soluble P (P<sub>H2O</sub>),  dilute salt-extractable P (P<sub>ex</sub>), microbial biomass P (P<sub>mic</sub>) and total labile P (P<sub>labil</sub>). Multifactor ANOVA revealed that tree species did not influence contents of P<sub>t</sub>, P<sub>ex</sub> and P<sub>H20</sub>. However, there was a statistically significant effect of soil substrate and soil horizon on these forms of P. The factors tree species, soil substrate and soil horizon had statistically significant effect on P<sub>mic </sub>content whereas content of P<sub>labil</sub> was affected by tree species and soil horizon. Multiple Range Tests by tree species showed that soils under Scots pine contained significantly less P<sub>mic </sub>than soils under other tree species studied. There were no significant differences in P<sub>mic</sub> between the soils under silver birch, black alder and black locust. The soils under Scots pine contained also significantly less P<sub>labil</sub> than the soils under black locust and silver birch. Our study included P forms that are considered labile (except P<sub>t</sub>). The obtained results indicated that the effect of N-fixing trees on these forms of P was weak. Instead we noticed that Scots pine had negative effect on some forms of labile P. </p><p>The study was financed by The National Science Centre, Poland, grant No. 2018/31/B/ST10/01626.</p>

Resources and specificity of reclamation at the coal mining spoils

The article analyses Khakassia environmental conditions with the aim to estimate their resources and role in the efficient reclamation of coal mining spoils. The availability of potentially fertile soil substrate as a resource for large-scale reclamation was evaluated by the thickness of the quaternary clay and loamy bedrock layers, taking into account the amount of the substrate needed for reclamation. The availability of resources of the potentially fertile soil substrate was carried out by taking into account the thickness and soil bulk density of the humus horizon of the most fertile soils of the region, and considering the obtained estimayes within the framework of the methodical rules and normative regulations for optimal reclamation. The availability of hydrothermal resources was estimated by active temperature sums and hydrothermal coefficient. Overall the distribution of reclamation resources was found to be very uneven throughout the region. In the south of Khakassia with its large areas occupied by technogenic landscapes the reclamation resources were concluded to be in deficit, insufficient for carrying out the reclamation according with the optimal protocols. Such lack of resources is indirectly confirmed by prevailing areas occupied by self-revegetating coal mining spoils. The article also describes some successful reclamation examples where specific local environmental conditions were used in such a way as to decrease the effect of deficient resources, thus increasing the efficacy of the self-restoration of technogenic landscapes.

Characterization of the core bacteriobiome in the rhizosphere of greenhouse vegetables: taxonomic diversity and putative functions

The aim of the study. The aim was to profile 16S rRNA gene diversity and to assess functional potential of bacterial assemblages in the rhizosphere of some unconventional vegetables grown in protected greenhouse conditions in West Siberia. Location and time of the study. Novosibirsk, Russia, 2016. Methodology. At the end of the growing season in the middle of September the rhizosphere soil was collected from the plants of wax gourd (Benincasa hispida), bitter melon (Momordica charantia), kiwano (Cucumis metuliferus) and cowpea (Vigna unguiculata) grown on peat-based substrate in a polyethylene-protected greenhouse that has been in operation for more than 40 years. The metagenomic DNA was extracted and amplified with V3-V4 primers for 16S rRNA genes, and the amplicons sequenced with Illumina MiSeq. The obtained OTUs tables were used to predict putative functions by running through the FAPROTAX database. Main results. The rhizosphere bacteriobiome was dominated by Proteobacteria (32±11% of the total number of sequence reads), Acidobacteria (23±7%) and Actinobacteria (18±3%) phyla, together accounting for about three quarters of the rhizosphere bacteriobiome. In total 20 bacterial phyla were found. The rhizosphere bacteriobiome was surprisingly diverse with Shannon index ranging 7.0–7.5. The number of the observed operational taxonomic units (OTUs) per sample was very high, ranging 4,500–4,900, and the potential number of OTUs estimated as 5,100–5,700; all those OTUs were evenly and equitably represented in the bacteriobiome, and dominance indices (Simpson dominance and Berger-Parker) were very low. The main dominant OTU represented Bradyrhizobiaceae family and accounted for just 1% on average. Overall the study identified 27 OTUs belonging to the Bradyrhizobiaceae family, but only four of them were ascribed to nitrogen fixation by FAPROTAX. Function prediction by FAPROTAX also suggested that bacteriobiome had a marked potential for the carbon cycle, denitrification, aromatic compound and plant polymer degradation, but no plant pathogens. The biggest difference in rhizosphere bacteriobiome diversity was observed between the bitter melon and the other three vegetable crops: bitter melon had much increased abundance of Arthrobacter and Sphingomonas as compared with wax gourd, kiwano and cowpea, and increased number of bacterial species associated with aromatic compounds degradation. Conclusion. Based on the finding that the studied rhizosphere bacteriobiomes were very diverse, we conclude that the crops were able to recruit diverse microbiota from the peat-based soil substrate, which, in its turn, means that diverse soil substrate microbiota has been sustained over several decades of the greenhouse operation. All crops apparently shaped distinct bacteriobiomes in their rhizosphere, which ideally should be included into studies of plant-associated bacterial diversity profiles for breeding and sustainable production.

Propagation of phytosanitary clones by in vitro culture

This article presents the process of accelerated reproduction of healthy clones of grapes, including the following stages: growing young shoots of the original plants of clones, introducing tops into in vitro culture, microclonal cuttings, adaptation of microplants to ex vitro culture, transplanting into cassettes with a soil substrate, transferring plants to a greenhouse for growing to the condition of vegetative seedlings and planting in a pre-propagation mother stock. For the successful implementation of each of the above operations in the SPIHVFT, a Cultural Complex has been equipped, consisting of a number of interconnected premises: a sterile box, a culture chamber and a vegetation chamber. The use of this Complex allows multiplying the required number of plants during the year, to grow vegetative seedlings by the spring of the next year and plant them in the pre-propagation “Pre-base” mother plant. After a year, grafted vegetative seedlings grown from the vines of the mother plant were used for laying the mother stock.