Giuseppe De Mastro

Fate of zinc and silver engineered nanoparticles in sewerage networks

Engineered zinc oxide (ZnO) and silver (Ag) nanoparticles (NPs) used in consumer products are largely released into the environment through the wastewater stream. Limited information is available regarding the transformations they undergo during their transit through sewerage systems before reaching wastewater treatment plants. To address this knowledge gap, laboratory-scale systems fed with raw wastewater were used to evaluate the transformation of ZnO- and Ag-NPs within sewerage transfer networks. Two experimental systems were established and spiked with either Ag- and ZnO-NPs or with their dissolved salts, and the wastewater influent and effluent samples from both systems were thoroughly characterised. X-ray absorption spectroscopy (XAS) was used to assess the extent of the chemical transformation of both forms of Zn and Ag during transport through the model systems. The results indicated that both ZnO- and Ag-NPs underwent significant transformation during their transport through the sewerage network. Reduced sulphur species represented the most important endpoint for these NPs in the sewer with slight differences in terms of speciation; ZnO converted largely to Zn sulfide, while Ag was also sorbed to cysteine and histidine. Importantly, both ionic Ag and Ag-NPs formed secondary Ag sulfide nanoparticles in the sewerage network as revealed by TEM analysis. Ag-cysteine was also shown to be a major species in biofilms. These results were verified in the field using recently developed nanoparticle in situ deployment devices (nIDDs) which were exposed directly to sewerage network conditions by immersing them into a municipal wastewater network trunk sewer and then retrieving them for XAS analysis.

Lactic Acid Bacteria in Durum Wheat Flour Are Endophytic Components of the Plant during Its Entire Life Cycle.

ABSTRACT This study aimed at assessing the dynamics of lactic acid bacteria and other Firmicutes associated with durum wheat organs and processed products. 16S rRNA gene-based high-throughput sequencing showed that Lactobacillus, Streptococcus, Enterococcus, and Lactococcus were the main epiphytic and endophytic genera among lactic acid bacteria. Bacillus, Exiguobacterium, Paenibacillus, and Staphylococcus completed the picture of the core genus microbiome. The relative abundance of each lactic acid bacterium genus was affected by cultivars, phenological stages, other Firmicutes genera, environmental temperature, and water activity (aw) of plant organs. Lactobacilli, showing the highest sensitivity to aw, markedly decreased during milk development (Odisseo) and physiological maturity (Saragolla). At these stages, Lactobacillus was mainly replaced by Streptococcus, Lactococcus, and Enterococcus. However, a key sourdough species, Lactobacillus plantarum, was associated with plant organs during the life cycle of Odisseo and Saragolla wheat. The composition of the sourdough microbiota and the overall quality of leavened baked goods are also determined throughout the phenological stages of wheat cultivation, with variations depending on environmental and agronomic factors.

The role of arbuscular mycorrhizal fungi in alleviating salt stress in Medicago sativa L. var. icon

Medicago sativa L. is the most important forage crop in arid and semi-arid areas, where increased salinity is a major factor limiting plant growth and crop productivity. The role of arbuscular mycorrhizal (AM) fungus Glomus viscosum H.T. Nicolson strain A6 in protecting alfalfa plants from salt stress, induced by sodium chloride (NaCl), was studied in two ways. Firstly, the root systems of 3-month old M. sativa plants, both mycorrhizal (AM+) and non-mycorrhizal (non-AM) (M. sativa L. var. icon), were placed in solutions of increasing salt concentrations (0, 50, 100, 150, 200 mM NaCl) to study the wilting response. G. viscosum improved the tolerance to salinity stress and the benefit was expressed in terms of the time required to reach the T4 stage in the wilting experiment. Secondly, to evaluate the ability of the Glomus-alfalfa symbiosis to tolerate salt, a pot experiment was set up in a glasshouse in which 3-month old alfalfa plants (M. sativa var. icon) were grown in a peat substratum at three salinity levels (0, 100, 150 mM NaCl). The AM symbiosis stimulated plant height, leaf area, root density, fresh and dry plant weight under saline conditions. Furthermore, proline accumulation was higher in mycorrhizal M. sativa plants than in non-mycorrhizal plants under conditions of salt stress. These and other results indicated that the micropropagated selected clone of M. sativa var. icon, when in symbiosis with G. viscosum H.T. Nicolson strain A6, exhibited better growth and physiological activities under saline conditions than non-AM plants. The AM+ plants also had lower sodium and chloride concentrations in tissues than non-AM plants.

Alfalfa (Medicago sativa L.) clones tolerant to salt stress: in vitro selection

In order to quickly and efficiently evaluate the salt tolerance of alfalfa, salinity tests were conducted on Medicago sativa L. var. australis, var. icon, var. loi, and var. gea, under in vitro conditions. Pregerminated seeds of four varieties were subjected to five different NaCl concentrations (0, 50, 100, 150, 200 mM). The influence of saline stress was estimated on the basis of survival percentage, growth parameters, and electrolyte leakage. The seedlings surviving on the medium enriched with salt at the highest concentration were presumed to be tolerant and represented the mother plants for the production of in vitro clones. In the following step, the clones were evaluated in vitro to confirm the salt tolerance. The influence of mild salt stress (75 mM NaCl) on the growth parameters of selected clones was examined. At the end of this trial, the proline accumulation and sodium content in alfalfa shoots were also quantified. The results suggest an increased level of proline promotes salt tolerance. Medicago sativa L. var. icon is highly tolerant in comparison with the other varieties tested. In vitro selection of M. sativa L. varieties on salt-containing media allowed us to obtain clones with increased salinity tolerance.

Effectiveness of mycorrhizal fungi on globe artichoke (Cynara cardunculus L. var. scolymus) micropropagation

The effectiveness of two arbuscular mycorrhizal (AM) fungal isolates (Glomus intraradices and Glomus viscosum) in sustaining plant growth and the physiological activities of the micropropagated globe artichoke (Cynara cardunculus L. var. scolymus (L.) Fiori) were investigated during acclimatization and 90 days after plant establishment. All the mycorrhizal microplants survived transplant shock thus confirming the positive role of AM fungi colonization on ex vitro establishment. The growth increased in mycorrhizal plants, especially in plants inoculated with Glomus viscosum. Mycorrhizal plantlets showed higher stomatal conductance, which is probably necessary to supply the carbon needs of fungal symbionts. The SPAD (soil plant analysis development) data could be useful for plant management as a predictor for tissue nitrogen levels. The higher SPAD values in mycorrhizal plants are strictly related to a higher photosynthetic potential, and consequently to their better nitrogen nutrient status due to the symbiotic relationship. Regardless of the mycorrhizal performance in the host–fungus combination, the most efficient fungus for the artichoke microplants was Glomus viscosum.

Climate Variability Impact on Wheat Production in Europe: Adaptation and Mitigation Strategies

Increased carbon dioxide concentration, rise in temperature and drought stress are important key factors causing frequent occurrence of climate events. Important adaptation strategy such as modification of phenological pattern to avoid stressful period during plant development will be key feature in crop plants. In addition, comprehensive understanding of plants response to elevated CO2 concentration, temperature and drought stress alone or in combination will be needed to acclimatize crop plant to these changes. Study of climate variability impact on wheat production concerning mitigation strategies is need of time in order to reduce the risk of climate change on crop yield and growth. Similarly, information about the time in which climate variable(s) occurred in the field is important as the severity of its effect/their combined effect can vary largely. Agronomic practices such as cultivar choice, water and nitrogen supply, nutrients availability and growing conditions should be taken into account to design adaptation options. The failure of agriculture to adapt to climatic variability will impact global food, especially wheat production. A holistic approach will be paramount to sustaining agriculture and the vitality of the world in the face of climate change.

Essential oil diversity of Origanum vulgare L. populations from Southern Italy

Essential oils (EOs) belonging to 25 wild populations of Origanum vulgare L. samples, growing wild in different locations of Calabria Region (Southern Italy), were analyzed using gas chromatography-mass spectrometry. The quantitative and qualitative data showed EO concentrations ranging from 0.96 to 5.10% and 37 compounds detected, representing more than 80% of the total composition of the oils. By applying hierarchical cluster analysis on the basis of the EO constituents, two main groups and three subgroups were found, reflecting the variation in the chemical composition of EOs from wild oregano populations. The first group consisted of acyclic (linalool/linalyl acetate) chemotypes with a predominant presence of linalyl acetate; the second was characterized by chemotypes rich in cymyl-compounds, mainly carvacrol, thymol and γ-terpinene. The data obtained contribute to broaden the inventory of wild oregano populations from Calabria to plan programs for the selection of chemotypes with new and specific uses.

Effects of Conservative Tillage and Nitrogen Management on Weed Seed Bank after a Seven-Year Durum Wheat—Faba Bean Rotation

Conservative agriculture includes a range of management strategies with low energy inputs such as no-tillage, minimum tillage, and low application of fertilizers. Weed flora in arable fields is strictly affected by agronomic practices such as tillage and fertilization management. This study was conducted seven years after the beginning of a long-term—durum wheat–faba bean—rotation. It analyzes the combined effects on the soil seed bank of three different tillage systems (conservative, reduced, and conventional tillage) and two levels of nitrogen fertilization. The effects were investigated both using stepwise discriminant analysis and analysis of variance in order to find statistical differences among main factors and their interactions. The seed bank of Conyza canadensis, Papaver rhoeas, Solanum nigrum, Fallopia convolvulus, and Fumaria officinalis was higher in conservative or reduced tillage plots. The magnitude of the response to nitrogen supply varied among weed species. Conyza canadensis seemed to be favored by low nitrogen supply, whereas Sinapis arvensis by higher doses of nitrogen. Anagallis arvensis showed the lowest seed bank in conventionally tilled plots, without distinction of nitrogen supply. The results suggest that different tillage systems and, to a lesser extent, different nitrogen supply, produce changes in the seed bank size and composition, along the soil profile.

Dynamic and Assembly of Epiphyte and Endophyte Lactic Acid Bacteria During the Life Cycle of Origanum vulgare L.

Origanum vulgare L. (oregano) was chosen as suitable model to investigate the ability of the endophyte-microbiome, especially that of lactic acid bacteria, to develop specific interactions with the plant, mediated by the essential oils (EOs). Combined culture-dependent and -independent approaches analyzed the bacterial dynamic and assembly of Origanum vulgare L. throughout the life cycle. Epiphyte bacteria were more abundant than the endophyte ones. The number of presumptive lactic acid bacteria increased throughout oregano life cycle, according to the plant organ. Diverse species of lactic acid bacteria populated the plant, but Lactobacillus plantarum stably dominated both epiphyte and endophyte populations. High-throughput DNA sequencing showed highest epiphyte bacterial diversity at early vegetative and full-flowering stages, with blooming signing the main microbial differentiation among plant organs. Proteobacteria, Actinobacteria and Bacteroidetes, and Firmicutes and Cyanobacteria at lower abundance were the main phyla. Various genera were detectable, but oregano harbored mainly Methylobacterium, Sphingomonas, Rhizobium and Aurantimonas throughout phenological stages. Firmicutes epiphyte and endophyte microbiotas were different, with a core microbiota consisting of Bacillus, Exiguobacterium, Streptococcus, Staphylococcus and Lactobacillus genera. Bacillus dominated throughout phenological stages. High-throughput DNA sequencing confirmed the dominance of L. plantarum within the epiphyte and endophyte populations of lactic acid bacteria. Yields of EOs varied among plant organs and throughout plant life cycle. L. plantarum strains were the most resistant to the total EOs (mainly thymol and carvacrol) as extracted from the plant. The positive correlation among endophyte lactic acid bacteria and the EOs content seems confirm the hypothesis that the colonization within plant niches may be regulated by mechanisms linked to the synthesis of the secondary metabolites.