Diversity of the Morphometric and Biochemical Traits of Allium cepa L. Varieties.

Several Allium cepa L. varieties, representing a versatile set of vegetables widely utilized by consumers, are appreciated for their bioactive properties, including antimicrobial, anticarcinogenic, and antioxidant capacities. The aim of this study is to compare the morphometric characteristics and biochemical profiles of four cultivars of A. cepa, two of them represented by the perennial Sicilian landrace "Cipudda agghiarola" (Allium × proliferum (Moench) Schrader), widely known as the Egyptian walking onion (WO), and by the landrace "Cipudduzza" belonging to the variety known as aggregatum (ON), which were compared with two commercial cultivars of A. cepa var. cepa (onion), Stoccarda (OS) and Rossa Carmen (OR). The experimental trial was conducted in Catania (Sicily), following organic growing practices. The randomized complete block experimental design was adopted with one experimental factor, the genotype (GE) effect. The harvested plants were characterized for their main morphometric parameters, according to the International Plant Genetic Resources (IGPR) descriptors. The biochemical activity was assessed by analyzing the total phenolic content (TPC) and the total flavonoid content (TFC). The antioxidant capacity was determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging, ferric reducing antioxidant power (FRAP), and oxygen radical absorbance capacity (ORAC). The sugar profile (total sugars, sucrose, glucose, fructose, and fructooligosaccharides-FOS) and the volatile compounds by headspace-gas chromatography/mass spectrometry (HS-GC/MS) were also determined. The OR bulb exhibited the highest TPC (16.3 mg GAE/g d.w., p < 0.01) and TFC (8.5 mg QE/g d.w., p < 0.01), with the highest antioxidant capacity measured by the FRAP (27.1 µmol TE/g d.w., p < 0.01) and DPPH assays (46.2 µmol TE/g d.w., p < 0.01). The ON bulb showed the highest ORAC value (209 µmol TE/g d.w., p < 0.01). Generally, the bulbs were richer in sugars (584 mg/g d.w., p < 0.01) than the leaf blade (239 mg/g d.w., p < 0.01), except for OR. Significant interaction between the genotype and plant organ was noted in the volatile compound profiles (p < 0.05) except for total ketones and carboxylic acids, where higher content was observed in the leaf blade compared to the bulb, regardless of the genotype. These findings highlight WO's potential for use in ready-to-eat products, enhancing its market value.

From Waste to Green: Water-Based Extraction of Polyphenols from Onion Peel and Their Adsorption on Biochar from Grapevine Pruning Residues.

Onion peels (OP) are rich in bioactive compounds with a plethora of benefits for human health, but this valuable material is often wasted and underutilized due to its inedibility. Likewise, grapevine pruning residues are commonly treated as agricultural waste, but biochar (BC) obtained from this material has favorable characteristics as an adsorbent. This study investigated the potential of BC in removal of targeted polyphenolic compounds from OP extracts. The OP extracts were obtained adhering to green chemistry principles using deionized water amplified by three methods: maceration (MAC), ultrasound-assisted extraction (UAE), and microwave-assisted extraction (MAE). The extraction efficiency on the polyphenolic profile and antioxidant capacity was investigated with different extraction temperatures and solid-to-liquid (s/l) ratios. For further analysis, UAE at 90 °C with an s/l ratio of 1:100 was used due to higher polyphenolic compound yield. The BC adsorption capacity of individual polyphenols was fitted with the Langmuir and Freundlich isotherm models. Quercetin-3,4'-diglucoside obtained the highest R2 coefficient in both models, and the highest qmax value. The optimum conditions in the dosage experiment suggested an amount of 0.5 g of BC using 3 g/L extracts. The studied BC showed a high affinity for targeted phytochemicals from OP extracts, indicating its potential to be applied for the green adsorption of valuable polyphenolic compounds.

The Interplay of Physiological and Biochemical Response to Short-Term Drought Exposure in Garlic (Allium sativum L.).

The impacts of global climate change and a rapid increase in population have emerged as major concerns threatening global food security. Environmental abiotic stress, such as drought, severely impairs plants' morphology, physiology, growth, and yield more than many other environmental factors. Plants use a complex set of physiological, biochemical, and molecular mechanisms to combat the negative effects caused by drought-induced stress. The aim of this study was to investigate morphological, spectral, physiological, and biochemical changes occurring in 30 garlic accessions exposed to short-term drought stress in a greenhouse setting and to identify potential early drought-induced stress markers. The results showed that, on average, garlic plants exposed to drought conditions exhibited a decrease in assimilation, transpiration, and stomatal conductance of 39%, 52%, and 50%, respectively, and an average increase in dry matter and proline content of 10.13% and 14.29%, respectively. Nevertheless, a significant interaction between the treatment and accessions was observed in the investigated photosynthetic and biochemical parameters. The plants' early response to drought ranged from mild to strong depending on garlic accession. Multivariate analysis showed that accessions with a mild early drought response were characterized by higher values of assimilation, transpiration, and stomatal conductance compared to plants with moderate or strong early drought response. Additionally, accessions with strong early drought response were characterized by higher proline content, lipid peroxidation, and antioxidant capacity as measured by FRAP compared to accessions with mild-to-moderate early drought response.

Size Does Matter: The Influence of Bulb Size on the Phytochemical and Nutritional Profile of the Sweet Onion Landrace "Premanturska Kapula" (Allium cepa L.).

The Mediterranean area is especially rich in old, both sweet and pungent, varieties of onion. The synthesis of phytochemicals takes place concurrently with the overall development and maturation of vegetables; however, it is unclear whether there is a correlation between onion bulb size and antioxidant compound content, antioxidant capacity, and nutritional parameters and what the origin of these variations is. The aim of this work was to investigate the biochemical and nutritional aspects of the sweet onion landrace "Premanturska kapula", as well as to investigate the influence of onion bulb size on onion phytochemical and nutritional profile. The sweet onion landrace "Premanturska kapula" has a high soluble sugar content, a high antioxidant capacity, and a high phenolic compound content. Quercetin-3,4'-diglucoside and quercetin-4'-glucoside were the major flavonols, while protocatehuic acid was the major phenolic acid detected. The choice of onion bulb size can impact the profile of the sugars present, with large bulb sizes favoring higher sucrose and fructooligosaccharides content compared to small bulb sizes which were more abundant in glucose. The total sugars or bulb dry matter were not affected by bulb size. Phenolic compounds were more abundant in smaller bulb sizes, thus indicating a link between bulb development and phenolic compound allocation within the plant. This link possibly derived from agronomic practices such as bare-root transplants, or even open pollination which causes a broader genetic variability. From a consumer perspective, it can be a choice between the small and medium bulb sizes on one hand, which are more abundant in polyphenolics and simple sugars, or on the other hand, the larger bulbs which are more abundant in fructooligosaccharides known to carry excellent health benefits.

Effect of Geographical Location on the Phenolic and Mineral Composition of Chetoui Olive Leaves.

In this study, we investigated the influence of pedological parameters and variation of altitude on the mineral nutrients, phenolic compounds, and antioxidant activities of olive leaves. Samples of the Chetoui cultivar were collected from eight geographical locations with different altitudes. Levels of phenolic compounds varied according to the altitude. Classification of the locations revealed that altitude 1 (>500 m) was characterized by high levels of secoiridoids and simple phenols, while altitude 2 (500-300 m) and altitude 3 (<300 m) were higher in flavonoids. Levels of Mn, Ca and B in the leaves and level of Zn in the soil were significantly correlated with the abundance of oleuropein and luteolin-7-O glucoside, the most important phenols in Chetoui olive leaves. The results suggest that, in addition to pedological criteria, environmental conditions also influence the formation of phenolic compounds.

Biochar from Grapevine Pruning Residues as an Efficient Adsorbent of Polyphenolic Compounds.

Agricultural waste, which is produced in large quantities annually, can be a threat to the environment. Biochar (BC) production represents a potential solution for reducing the amount of grapevine pruning residues and, accordingly, the impact on the environment and climate change. Biochar produced by the process of pyrolysis from grapevine pruning residues was investigated and characterized to be applied as an adsorbent of polyphenolic compounds with the aim of using the waste from viticultural production to obtain a quality product with adsorption and recovery potential. Standards of caffeic acid (CA), gallic acid (GA), and oleuropein (OLP) were used as polyphenolic representatives. The obtained data were fitted with the Langmuir and Freundlich isotherms models to describe the adsorption process. The best KL (0.39) and R2 (0.9934) were found for OLP using the Langmuir model. Furthermore, the adsorption dynamics and recovery potential of BC were investigated using an adapted BC column and performed on an HPLC instrument. The adsorption dynamics of biochar resulted in the adsorption of 5.73 mg CA g-1 of BC, 3.90 mg GA g-1 of BC, and 3.17 mg OLP g-1 of BC in a 24 h contact. The online solid phase extraction of the compounds performed on an HPLC instrument yielded a recovery of 41.5 ± 1.71% for CA, 61.8 ± 1.16% for GA, and 91.4 ± 2.10% for OLP. The investigated biochar has shown a higher affinity for low-polar compound adsorption and, consequently, a higher polar compound recovery suggesting its potential as an efficient polyphenolic compound adsorbent.

Phenolic Content, Amino Acids, Volatile Compounds, Antioxidant Capacity, and Their Relationship in Wild Garlic (A. ursinum L.).

Allium ursinum L. is a wild relative of garlic, and it is abundant in many antioxidant compounds. Sulfur compounds, primarily cysteine sulfoxides (CSOs), are converted through several reactions into various volatile molecules, which are considered the principal flavor compounds of Alliums. In addition to secondary metabolites, wild garlic is abundant in primary compounds, such as amino acids, which serve not only as building blocks for the health-promoting sulfur compounds but also as antioxidants. The aim of this study was to investigate the link between individual amino acid contents, the total phenolic content, and the profile of volatile compounds as well as their influence on the antioxidant capacity of both the leaves and bulbs of wild garlic populations in Croatia. Both univariate and multivariate methods were used to study the differences in the phytochemical compositions among the wild garlic plant organs and the link between individual compounds and antioxidant capacity. Both the plant organ and location, as well as their interaction, have a significant impact on the content of total phenolic content, amino acids, volatile organic compounds, and the antioxidant capacity of wild garlic.

Garlic Ecotypes Utilise Different Morphological, Physiological and Biochemical Mechanisms to Cope with Drought Stress.

Drought negatively affects plants by altering morphological, physiological and metabolic processes and ultimately reducing yields. Garlic (Allium sativum L.), an important member of the Alliaceae family, is also sensitive to drought and maximizing the yield of garlic bulbs is largely dependent on water availability. The objective of this study was to determine the effects of drought stress on morphological and physiological characteristics, as well as on phenolic, sugar, inulin and free amino acid content and antioxidant activity in two Croatian garlic ecotypes, 'Istarski crveni' (IC) and Istarski bijeli (IB). Drought was induced by using polyethylene glycol 8000 (PEG) solution (-0.6 MPa) starting 21 days after clove planting and lasted for 20 days. Drought reduced plant height, number of leaves and plant weight, but increased root length in both ecotypes compared to the control treatment. Among the physiological parameters, significant differences were observed between the two ecotypes studied in the spectral characteristics of the leaves, namely reflection in red, green and blue, VAL, values of the vegetation indices related to the chlorophyll content (CHI, GI), and the anthocyanin content (ARI). Ecotype IC showed higher antioxidant activity in the control treatment due to higher total phenolic content (TPC), but under drought conditions higher DPPH radical scavenging activity was determined in ecotype IB and higher values of FRAP in IC. Sucrose and glucose generally decreased under drought, while inulin increased in IB but decreased in IC. Total free amino acid content increased under drought in both ecotypes. In conclusion, drought tolerance of IB might be associated with increased accumulation of inulin and higher levels of amino acids, especially those shown to contribute to drought resistance. In IC, drought tolerance is associated with an increase in some amino acid compounds and better root growth in depth, probably due to a more efficient translocation of sucrose to the underground part of the plant.

Phosphorus Use Efficiency of Leafy Brassica sp. Grown in Three Contrasting Soils: Growth, Enzyme Activity and Phosphorus Fractionation.

Plant adaptations to low soil phosphorus (P) availability have been intensively studied in Brassica sp. in an attempt to identify the mechanisms involved in P uptake and utilization. The present pot experiment was conducted to evaluate the relationships between plant shoot and root growth, P uptake and use efficiency parameters, and P fractions and enzyme activity, in two species grown in three soil types. The aim of this study was to determine whether adaptation mechanisms are soil-dependent. Two kale species were grown in soils typical for coastal Croatia (terra rossa, rendzina, and fluvisol) with low P availability. Plants grown in fluvisol had the highest shoot biomass and accumulated most P, whereas plants developed the longest roots in terra rossa. Phosphatase activity differed among soils. P use efficiency differed among soils and species. Genotype IJK 17 showed better adaptation to low P availability, which was related to better uptake efficiency. In general, soils differed in inorganic and organic P fractions in rhizosphere soil, but no difference between genotypes was found. The activities of alkaline phosphatase and phosphodiesterase were negatively correlated with most organic P fractions, suggesting their function in the mineralization of soil organic P. Kale species activate different mechanisms of P uptake and utilization when grown in contrasting soil types, suggesting that specific responses to the soil type were more important than the genotypic difference.

Effect of olive-processing technology on the utilization of olive mill pomace as a soil amendment.

In the Mediterranean basin, the treatment and disposal of olive mill pomace (OMP) remain a salient environmental issue for the olive oil-producing industry. This study assesses the effects of olive-processing technology (three-phase and two-phase systems) on the potential use of OMP as a soil amendment. Samples from 12 Croatian olive mills were analyzed for their total phenolic content (TPC), residual oil fraction, and elemental concentration. The samples were profiled using Fourier transform infrared spectroscopy (FT-IR) and structurally characterized using scanning electron microscopy-energy-dispersive X-ray spectroscopy (EDS). Compared to three-phase samples, two-phase OMP was more acidic (pH 4.5 vs. 5.0), with a higher TPC (3835 vs. 1576 mg/kg fresh weight), oil content (11.7% vs. 7.5% d.w., where d.w. is dry weight), electrical conductivity (EC, 5.1 vs. 3.0 mS/cm), and levels of calcium (Ca, 1.34 vs. 1.20 g/kg d.w.) and copper (Cu, 10.4 vs. 7.0 mg/kg d.w.). Similar values of carbon/nitrogen (C/N; 61 vs. 72), N (10 vs. 8.1 g/kg d.w.), phosphorus (1040 vs. 691 mg/kg d.w.), and potassium (K, 13.7 vs. 8.1 g/kg d.w.) were observed. The amounts of chromium, copper, nickel, and zinc were below EC limits in both cases. The EDS mapping revealed that Ca was concentrated at sharp-edged OMP particles while K was evenly distributed, suggesting that pelletized OMP compost is preferable for amending soil to obtain a homogeneous distribution of nutrients. It was also possible to distinguish between OMPs based on oil and lignin absorption bands in their FT-IR spectra. According to the obtained results, composting is recommended for both types of OMP to produce a safe product for amendment purposes.

Comprehensive Volatilome Signature of Various Brassicaceae Species.

To investigate in detail the volatilomes of various Brassicaceae species, landraces, and accessions, and to extract specific volatile markers, volatile aroma compounds were isolated from plant samples by headspace solid-phase microextraction and analyzed by gas chromatography/mass spectrometry (HS-SPME-GC/MS). The data obtained were subjected to uni- and multivariate statistical analysis. In general, two cabbage (Brassica oleracea L. var. capitata) landraces emitted the lowest amounts of volatiles generated in the lipoxygenase (LOX) pathway. Wild species Brassica incana Ten. and Brassica mollis Vis. were characterized by relatively high trans-2-hexenal/cis-3-hexen-1-ol ratio in relation to other investigated samples. A Savoy cabbage (Brassica oleracea L. var. sabauda) cultivar and three kale (Brassica oleracea L. var. acephala) accessions exhibited particular similarities in the composition of LOX volatiles, while the LOX volatilome fraction of B. incana and B. mollis partially coincided with that of another wild species, Diplotaxis tenuifolia L. Regarding volatiles formed in the glucosinolate (GSL) pathway, Savoy cabbage and wild species B. incana, B. mollis, and D. tenuifolia showed more intense emission of isothiocyanates than cabbage and kale. Diplotaxis tenuifolia showed a rather limited production of nitriles. The results of this study contribute to the general knowledge about volatile composition from various Brassicaceae species, which could be exploited for their better valorization. Future studies should focus on the influence of various environmental, cultivation, and post-harvest factors to obtain data with a higher level of applicability in practice.

Valorization of Olive Leaf Polyphenols by Green Extraction and Selective Adsorption on Biochar Derived from Grapevine Pruning Residues.

Given today's increasingly intensive agriculture, one key problem area considers the valorization and reuse of wastes from food and agricultural production with minimal impact on the environment. Due to its physicochemical characteristics, biochar (BC) derived from grapevine pruning residue has shown considerable potential for use as an adsorbent. High-value phytochemicals found in abundance in the olive leaf (OL) can be employed in many different industrial sectors. The potential application of BC in the removal of specific polyphenolic components from OL extracts has been investigated in the present study. Water, as the most available and greenest of solvents, was investigated as to its use in the extraction of polyphenols, which was carried out by comparing maceration, ultrasound-assisted extraction, and microwave-assisted extraction, considering different temperatures and solid-to-liquid (s/l) ratios. The BC adsorption capacity of selected polyphenols was fitted with both the Langmuir and Freundlich isotherm models. The Freundlich model fitted better relative to OL polyphenols adsorption. Oleuropein was the most abundant compound identified in the extracts, obtaining the highest Kf value (20.4 (mg/g) × (L/g)n) and R2 coefficient (0.9715) in the adsorption on the biochar's surface. The optimum conditions in the dosage experiment suggest the use of 0.5 g of BC using 3 g/L extracts, with an exception for oleuropein and hydroxytyrosol, for which the highest biochar dose (2.5 g) performed better. Considering the compounds' concentrations and the BC dose, BC from grapevine pruning residues demonstrated a potential use in the uptake of specific polyphenols from olive leaves, making it a promising adsorbent for such applications.

Non-Aerated Common Nettle (Urtica dioica L.) Extract Enhances Green Beans (Phaseolus vulgaris L.) Growth and Soil Enzyme Activity.

One of the limiting factors in organic farming is the scarcity of allowed fertilizers and chemicals for plant protection. Plant and compost extracts are a promising solution for fertilization because of their positive effect on plant growth and soil microbial activity. Nettle extract was already successfully applied to some vegetables. Not-aerated nettle extract, obtained from dry nettle leaves, was applied in experiments with green beans in a quantity of 1 L per pot at two-day intervals was studied. A three-factorial experimental design was applied with two soil types (brown-Calcic Gleysol and red-Eutric Cambisol), soil disinfection with dazomet or not, and irrigated with nettle extract or water. Nettle extract application increased all above-ground traits; plant height, leaf area, flower buds, shoot dry weight at flowering, pod length, pod diameter, and shoot dry weight at harvest by 49%, 66%, 43%, 36%, 11%, 9%, and 37%, respectively, the root length at harvest by 59%, total yield by 48%, soil respiration by 91% and 74% in two soil types, and alkaline phosphatase by 30%. Dehydrogenase activity was enhanced by nettle extract application on red soil, while nettle extract application had no effect on root nodulation. The nettle extract application benefits in green bean organic production were attributed to the nutrients and other components present in the extract and not to nitrogen fixation. The optimization of the dose of the extract and experiments in real conditions of green bean production would be the next step toward the implementation of nettle extract as an organic fertilizer.

Influence of sewage sludge stabilization method on microbial community and the abundance of antibiotic resistance genes.

Municipal sewage sludge (MSS) and other biosolids are of high interest for agriculture. These nutrient-rich organic materials can potentially serve as organic fertilizers. Besides an increase of organic matter in soil, other positive effects were shown after their application. Especially the positive influence on circular economy increased the attention paid to management of MSS in recent years. Unfortunately, the use of sewage sludge has some drawbacks. Biosolids are frequently polluted with heavy metals, xenobiotic organic compounds and industrial chemicals, which may be hazardous for the environment and humans. Here, we investigated the influence of stabilization method and the size of wastewater treatment plant on the structure of microbial communities as well as the abundance of antibiotic resistance genes (ARG) and mobile genetic elements (MGE). All tested ARG and MGE were detectable in almost all of the samples. Interestingly, the presence of MGE as well as particular heavy metals correlated positively with the presence of several ARG. We conclude that the distribution of ARG and MGE in biosolids originated from municipal wastewater treatment plants, cannot be explained by the size of the facility or the applied stabilization method. Moreover, we postulate that the presence of pollutants and long-term impacts should be assessed prior to a possible use of sewage sludge as fertilizer.

The Phytochemical and Nutritional Composition of Shallot Species (Allium × cornutum, Allium × proliferum and A. cepa Aggregatum) Is Genetically and Environmentally Dependent.

Shallots are a perennial plant from the Alliaceae family, classified with the common onion under the name of the Allium cepa Aggregatum group. The term shallot is also used for diploid and triploid viviparous onions, known as Allium × proliferum (Moench) Schrad and Allium × cornutum Clementi ex Vis., respectively. In this study, we compared the dry matter, pyruvic acid content, sugar content, flavonoid content, antioxidant capacity and mineral composition of 34 shallot accessions falling into three shallot species (Allium × cornutum, Allium × proliferum and A. cepa Aggregatum). Shallot accessions belonging to the A.× cornutum and A. × proliferum groups are characterized by high dry matter content (around 25%), of which a little less than 50% is formed of inulin-type sugars, polysaccharides, considered an excellent prebiotic with beneficial effects on human health. On the other hand, accessions belonging to the A. cepa Aggregatum group have lower dry matter content and, as a result, lower pungency (measured as pyruvic acid content), making them more suitable for fresh consumption by a broader range of consumers, but, at the same time, abundant in phenolic compounds, especially quercetin and isorhamnetin glycosides. We also observed a greater biodiversity among accessions within the A. cepa Aggregatum group in all the analyzed physico-chemical parameters compared to the other shallot groups. The investigated shallot accessions have an excellent in vitro antioxidant capacity, as well as excellent nutritional properties.

Bioactive Properties, Volatile Compounds, and Sensory Profile of Sauerkraut Are Dependent on Cultivar Choice and Storage Conditions.

Sauerkraut is produced by cabbage fermentation either spontaneously or by adding lactic acid bacteria. Although commercial cabbage cultivars are more desirable due to their higher yield and uniformity, traditional cultivars are highly prized for their unique sensory characteristics and suitability for fermentation. The aim of this study was to investigate the properties of sauerkrauts from traditional cabbage cultivars ('Brgujski' and 'Zminjski') compared to commercial samples, and to unravel the effects of ambient (18 °C) and cold storage (4 °C) on sauerkraut properties. Higher total phenolic contents and total antioxidant capacities measured by both FRAP and DPPH methods were observed for sauerkrauts from traditional cultivars. In total, 32 volatile compounds were identified, and differences in the volatile profile were observed among the investigated sauerkrauts. The sensory properties of traditional cabbage cultivars were on par, or even better, compared to those of commercially available sauerkraut products. The cold storage conditions characteristic of commercial environments preserved the total antioxidant capacity, the red to green color ratio (a), as well as the lightness (L) of sauerkraut compared to the ambient temperatures characteristic of domestic conditions, indicating the preservation of bioactive compounds responsible for the purple cabbage head coloration of the investigated traditional cultivars.

Biophenolic Profile Modulations in Olive Tissues as Affected by Manganese Nutrition.

Manganese (Mn) is an essential element that intervenes in several plant metabolic processes. The olive tree, and its fruits and leaves, are known as a source of nutraceuticals since they are rich in biophenols. However, there is still a serious lack of data about biophenolic distribution in olive stems and roots under Mn fertilisation. In this context, our study aimed to examine the effects of Mn fertilisation on the biophenolic profile in the leaves, stems, and roots of the 'Istarska bjelica' olive cultivar. The experiment was set up in a greenhouse, during a period of five months, as a random block design consisting of three treatments with varying Mn concentrations in full-strength Hoagland's nutrient solution (0.2 µM Mn, 12 µM Mn, and 24 µM Mn). The obtained results indicate that the amount of Mn in the examined olive plant tissues was significantly higher under 12 µM Mn and 24 µM Mn treatments compared to that of the 0.2 µM Mn treatment. While the concentration of biophenols varied in roots depending on the compound in question, a strong positive impact of the increased Mn concentration in nutrient solution (12 µM Mn and 24 µM Mn) on the concentrations of the main biophenolic compounds was observed in stems. The concentration of oleuropein in leaves almost doubled at 24 µM Mn, with the highest Mn concentration, as compared to the 0.2 µM Mn treatment. The obtained results led to the conclusion that the supply of Mn could enhance the concentration of some biologically active compounds in olives grown hydroponically, implying a critical need for further investigation of Mn fertilisation practices in the conventional olive farming system.

Effect of sewage sludge derived compost or biochar amendment on the phytoaccumulation of potentially toxic elements and radionuclides by Chinese cabbage.

This study set out to evaluate the effect of using sewage sludge-derived compost (SSC) or biochar (SSB) as a soil amendment on the phytoaccumulation of potentially toxic elements, PTE (Cd, Cr, Cu, Ni, Pb, Zn) and natural radionuclides (238U and 232Th) by Chinese cabbage (Brassica rapa L. subsp. pekinensis (Lour.) Hanelt) in terra rossa and rendzina soils, which are the two common soil types in Croatia. The experiment consisted of a greenhouse pot trial using a three-factor design where soil type, sludge post-stabilisation procedure and amendment rate (12 and 120 mgP/L) were the main factors. At harvest, the concentrations of analytes in the substrate, leaves and roots were measured, from which the edible tissue uptake (ETU) and concentration ratios (CR) were determined. Also, the average daily dose (ADD) and hazard quotient (HQ) were determined to assess the health risk, as well as soil contamination factor (CF). The results showed that neither adding SSC nor SSB affected the soil loading at the rates applied, suggesting a low risk of soil contamination (CF ≤ 1). The ETU of Cd, Cu, and Zn were 0.0061, 1.23, and 0.91 mg/plant from compost-amended soil and 0.0046, 0.78 and 0.65 mg/plant for biochar-amended soil, respectively. This difference suggests that their ETU was higher in compost-amended soils than in soils treated with biochar. The CR data indicate that the bioavailability of Cu (CR of 5.30) is highest at an amendment rate of 12 mgP/L, while for Zn (CR of 0.69), the highest bioaccumulation was observed with an amendment rate of 120 mgP/L. Translocation of Cr, Ni, Pb and 238U to the leaves was limited. Overall, the HQ (<1) for Cd, Cu and Zn in the edible parts confirmed that consuming Chinese cabbage does not threaten human health. Similarly, the daily intake of 232Th remained below the limit (3 µg) set by ICRP, suggesting no radiological risk. Finally, although the amendment rate, which was 10-times the amount stipulated in Croatian regulation and the CR ranged from 0.007 to 5.30, the precautionary principle is advised, and the long-term impact of sewage sludge derived compost or biochar on different plant groups (incl. root vegetables) at the field-scale is recommended.

Fruit quality and volatile compound composition of processing tomato as affected by fertilisation practices and arbuscular mycorrhizal fungi application.

The effects of different fertilisation treatments with arbuscular mycorrhizal fungi (AMF) inoculation on AMF root colonisation, fruit yield, nutrient and total phenol contents, volatile compound composition, and sensory attributes of tomato (Solanum lycopersicum L.) were investigated. Mineral, organic, and mineral + organic fertiliser application positively affected tomato yield (35%-50%) and phosphorus concentration (24%-29%) compared with controls. AMF application had a significant impact on the total nitrogen (+9%), manganese (+12%), and hydrophilic phenol (+8%) contents in the fruit. Volatile compounds were affected by the interactive effects of fertilisation and AMF application. The response of tomato fruit sensory quality indicators was relatively modest, with only a few sensory characteristics affected to a lesser extent. Although tomato showed susceptibility to field-native AMF, particular combinations of fertilisation and AMF inoculation were more effective at improving the quality parameters of tomatoes under field conditions applied in this study.

Temporal Variation of Phenolic and Mineral Composition in Olive Leaves Is Cultivar Dependent.

In order to investigate the potential of various olive cultivars and leaf sampling times for phytochemical farming practice in Croatia, phenolic and mineral composition was determined in olive leaves of four Croatian cultivars and Italian cultivar Leccino collected at three occasions, in October 2017, January 2018, and March 2018. Istarska bjelica turned out to have the largest phytochemical potential among the investigated cultivars due to steady high oleuropein concentrations found in its leaves. The concentration of main phenolic components in Istarska bjelica leaves changed only slightly during the sampling period, suggesting the possibility of its higher capability for low air temperatures stress resistance and different metabolic response compared to the other studied cultivars. Low air temperatures increased the oleuropein level and antioxidant activity in leaves of Leccino, Oblica, Levantinka, and Drobnica cultivars, which may be of crucial phytochemical farming interest. Each of the investigated olive cultivars was characterized by a specific leaf mineral nutrient composition, which could have had a specific role in their interplay with phenols.