Evaluation of postharvest storability of Ponkan mandarins stored at different temperatures

ABSTRACT The effects of storage temperature on postharvest storability, quality attributes and antioxidant enzyme activities of harvested Ponkan mandarins were investigated. Fresh fruits were randomly divided into four groups and stored at different temperatures [5 ± 1 °C (S5), 10 ± 1 °C (S10), 15 ± 1 °C (S15), and 20 ± 1 °C (S20 or control)] for 120 days. The results indicated that, compared with the control fruit, low-temperature storage at 10 °C significantly delayed the increase in fruit decay rate, weight loss, citrus colour index, respiration intensity, relative electrical conductivity, the accumulation of hydrogen peroxide and malondialdehyde, retarded the decline in L* value, retained high contents of total soluble solid, titratable acid, vitamin C, total phenol and total flavonoid, as well as higher activities of antioxidant enzymes – superoxide dismutase, catalase, peroxidase and ascorbic peroxidase. The principal component analysis results showed that low-temperature storage significantly maintained the postharvest quality of Ponkan mandarins, with fruit stored at 10 °C having no significant difference from the fruit stored at 5 °C, but markedly higher than those fruit stored at 15 °C. The comprehensive result of single-factor analysis and PCA showed that 10 °C could be used as the optimum storage temperature for improving the postharvest storability of Ponkan mandarins.

Salicylic acid effect on the mechanism of Lelliottia amnigena causing potato soft rot

Salicylic acid (SA) plays an important role in protecting plants from biotic stresses. Lelliottia amnigena is a newly identified potato soft rot pathogen and there are no adequate studies on this soft rot pathogen. Therefore, this paper focussed on the effect of SA on the mechanism under which L. amnigena causes potato soft rot. L. amnigena was examined and detected to secrete pectinase, proteases, pectin lyase and cellulase, which are the most important pathogenic enzymes involved in the production of plant diseases. Sterilised healthy potato tubers were inoculated with 0.2 mL of L. amnigena suspension (3.69 CFU · mL−1 × 107 CFU · mL−1). After 24 h, 200 μL of four different SA concentrations (0.5 mM, 1.0 mM, 1.5 mM and 2.0 mM) were used to treat the tubers. Co-culture of L. amnigena and SA significantly reduced the activity of pectinase, protease, pectin lyase and cellulase by an average of 33.8%, 43.4%, 67.7% and 46.9%, across the four concentrations (0.5 mM, 1.0 mM, 1.5 mM and 2.0 mM), respectively, compared to the control. The average disease index was reduced by 54.7% across the four SA concentrations. Treatment with SA induced transcriptional levels of the superoxide dismutase, peroxide, catalase and glutathione S-transferase across the four levels by an average of 3.87, 3.25, 3.97 and 3.94-fold, respectively, compared to control. Based on our results, we could state that SA could reduce the activities of these extracellular enzymes produced by L. amnigena by modulating both enzymatic and non-enzymatic antioxidant activities and gene expression that induce natural resistance in plants against bacterial infections.

Zinc sulphate or zinc nanoparticle applications to leaves of green beans

The green bean (Phaseolus vulgaris L.) is a very widely grown food crop that contributes significantly to human dietary needs in many countries due to its high content of protein. This study evaluates foliar applications of ZnSO4 versus that of zinc oxide nanoparticles (ZnO NPs) to leaves of the green bean cv. ‘Strike’ and records the plant responses in terms of Zn uptake and concentrations of photosynthetic pigments and bioactive compounds. The experiment was conducted under greenhouse conditions in Chihuahua, Mexico, with a completely randomised experimental design with 10 replicates. The two treatments were foliar applications of either an aqueous solution of ZnSO4 or an aqueous suspension of ZnO NPs (both 150 mg · L−1). The application of ZnO NPs significantly increased concentrations of Zn2+ in the leaflets, roots, stems and pods of chlorophylls a and b (values 15.40 μg · g−1 and 11.64 μg · g−1, respectively). Sucrose concentration was also increased by Zn2+ applications, but no differences were found in total phenols (TP), total flavonoids (TFl) or antioxidant capacity (AC). In the pods and seeds, Zn2+ application left sucrose and TFl concentrations unchanged, but the TP increase was significant. The AC was affected by both zinc sources and only in the pods. The applications of ZnSO4 or ZnO NPs significantly increased the biomass accumulation (79.10 g · p−1 and 84.70 g · p−1 DW) and yield (55.64 g · p−1 and 53.80 g · p−1 FW). These results suggest that the application of ZnO NPs could represent a worthwhile biofortification strategy in the commercial production of green bean cv. ‘Strike’.

Reduction of chilling injury of ‘Washington’ navel orange fruits by melatonin treatments during cold storage

Cold storage is used to improve the efficiency of storage and handling of orange fruits, but the fruits are exposed to chilling injury (CI). Antioxidant enzymes are part of the antioxidant defence system against CI of ‘Washington’ oranges during cold storage, which controls storage/handling efficiency. In this study, melatonin (ME) was used on fruits to reduce cold damage. To assess the action of ME influences; fruits were picked from the tree at the commercial maturity stage and divided into two groups that were uniform in size and colour. Then, they were immersed in ME solution at 0 mmol, 10 mmol, 100 mmol or 1,000 mmol for 20 min at 20 ± 1 °C. The treated fruits were stored at 4 ± 1 °C and 95 ± 1% RH for 4 weeks during 2019 and 2020 seasons. The physical and chemical characteristics of the stored fruits were measured every week up to the end of the storage period. Results indicated that immersing fruits in 1,000 μM ME minimised the CI-index and the water loss%, while preserving the orange peel colour (h°) during cold storage. On the other hand, the same treatment caused slight changes in soluble solid content (SSC%), maintained ascorbic acid (AA) content and the stability of total acidity (TA%), enhanced the antioxidant enzymes activities (AEAs) such as ascorbate peroxidase (APX), catalase (CAT), and superoxidase dismutase (SOD) and also reduced the rate of malondialdehyde (MDA) and ion leakage (IL) during cold storage. Moreover, it minimised hydrogen peroxide (H2O2) and superoxide anion (O2 •−) production and caused pronounced results to be exhibited in antioxidant capacity. Overall, the 1,000 μM ME treatment for orange fruits afforded more tolerance against cold storage stress.

Hoverflies (Syrphidae: Diptera) in areas contaminated with heavy metals (Cd, Zn, Pb)

The aim of the research was to study the diversity of hoverflies (Syrphidae: Diptera) living in areas under the influence of heavy metal emissions (Cd, Zn and Pb). Although the area of the Olkusz Ore-bearing Region (OOR), where the research was partially conducted, belongs to the contaminated regions, where a relatively high species richness of Syrphids has been noted. During the research period, a total of 1,180 syrphids, belonging to 165 species were caught, which constitutes 39.76% of all the Polish Syrphidae fauna. These species represented all the trophic groups with the dominance of zoophagous species (48.48%); however, the most numerous (quantitatively abundant) were saprophagous. Among the collected syrphids, common and numerous species, such as: E. arbustorum (LINNAEUS, 1758), E. tenax (LINNAEUS, 1758), Episyrphus balteatus (DE GEER, 1776) and S. pipiens (LINNAEUS, 1758), as well as rare species such as Callicera aenea (FABRICIUS, 1777) (NT), Chalcosyrphus piger (FABRICIUS, 1794) (DD), Epistrophe ochrostoma (ZETTERSTEDT, 1849) (VU), Orthonevra geniculata (MEIGEN, 1830) (DD), Rhingia rostrata (LINNAEUS, 1758) (DD), Sphegina sibirica STACKELBERG, 1953 (LC) and Spilomyia diophthalma (LINNAEUS, 1758) (NT), were noted. Eleven of the collected species have been included in the Polish Red List of Endangered Species. Melangyna ericarum (COLLIN, 1946) is recorded as a new one among the Polish fauna. Numerous observations did not indicate that the area covered by the study was characterised by a significantly lower species diversity compared to other sites. In fact, the samples taken were usually characterised by a relatively high biodiversity. The obtained results may suggest that anthropogenic activities, including those leading to environmental pollution with heavy metals and to a strong transformation of natural habitats, do not completely destroy biodiversity, and in some cases leave space for nature to create habitats where even rare species of organisms such as Syrphidae can develop.

Bibliometric analysis of strawberry (Fragaria × ananassa Duch.) research from Plant Sciences category based on Web of Science

Strawberry (Fragaria × ananassa Duch.) is one of the most significant horticultural cash crops in the world. The study aimed to identify and analyse the 2,930 articles and review type papers of strawberry research from the Plant Sciences category based on the Web of Science. Papers mainly written in English (2,894, 98.771%), were from a total of 8,838 authors, 96 countries/territories, 1,845 organisations and published in 197 journals and book series. The top seven core journals are ranked as Plant Disease (252, 8.601%), Phytopathology (229, 7.816%), Plant Pathology (93, 3.174%), Frontiers in Plant Science (89, 3.308%), Canadian Journal of Plant Science (86, 2.935%), European Journal of Plant Pathology (86, 2.935%) and Journal of Experimental Botany (86, 2.935%), and these journals each published >86 papers. The top five countries and regions were the USA, People's Republic of China, Spain, Canada and England. The top five organisations were the University of Florida, USDA ARS, University of Malaga, University of California Davis, Agriculture and Agri-Food Canada. The top five authors are Peres, Natalia A. (Peres, Natalia; Peres, N.A.); Madden, LV; Munoz-Blanco, Juan (Munoz-Blanco, J); Schwab, Wilfried (Schwab, W) and Ellis, MA, each published >25 papers. All keywords of the strawberry research from the Plant Sciences category were separated into 11 clusters for different research topics. Visualisations offer exploratory information on the current state in a scientific field or discipline as well as indicate possible developments in the future. The review could provide a valuable guide for designing future studies.

Biochemical composition and shape-dimensional traits of rosehip genotypes

In the present study, the biochemical composition and shape and dimensional traits of 25 rosehip (Rosa canina) genotypes were investigated. The shape and dimensional traits were determined by image processing technique. Seed-propagated rosehip genotypes belonging to R. canina were collected from the natural flora of Mesudiye (Ordu) and Talas (Kayseri) districts. Antioxidant activity (39.510–72.673 mmol · kg−1), total flavonoids (287.80–1,686.20 mg quercetin equivalent (QE) · kg−1) and total phenolics (38,519.40–79,080.60 mg gallic acid equivalent · kg−1) of the genotypes exhibited large variations. Width (12.2 mm) and thickness (12.5 mm) of fruits averages were found to be close to each other. The genotypes exhibited fruit lengths between 12.0 mm and 29.5 mm. Average projected area at horizontal orientation (179.7 mm2) was greater than the projected area at vertical orientation (120.4 mm2). Sphericity average was calculated as 71.4%. According to principal component (PC) analysis, the most important dimensional traits discriminating genotypes from each other were identified as surface area, geometric mean diameter and volume. In terms of shape attributes, distinctive differences were observed in sphericity, circularity, elongation and surface closure rates (SCR) of the genotypes. According to elliptic Fourier analysis (EFA), genotypes look like a sphere. In terms of shape, there were long, spherical, flat bottomed, pointed bottomed and asymmetric-looking genotypes indicating how environment and genotype affect the fruit shape. The greatest shape variation was transverse contraction and expansion. According to the clustering analysis for shape attributes, rosehip genotypes were classified into six groups. Dendrogram, scatter plots of linear discriminant analysis and paired comparison test results put forth the shape differences of the genotype successfully.

Improvement of the quality in hydroponically grown fresh aromatic herbs by inducing mild salinity stress is species-specific

Profitable hydroponic production requires high quality fresh water, which is often not available for agricultural use, while desalinisation of salty water is an expensive and unsustainable technology. In the present study, we assessed the effect of mild salinity stress during the soilless cultivation of fresh peppermint and spearmint in the floating system on biomass yield, produce quality and plant secondary metabolite content. Peppermint and spearmint plants were grown for 25 days on a nutrient solution (NS) supplemented with three different NaCl concentrations (0 mM, 10 mM or 20 mM NaCl). The plant height, root length, fresh and dry weight were recorded and composition was determined on fresh tissue. The composition of essential oil was determined upon hydrodistillation and that of polyphenolic compounds by targeted ultra-performance liquid chromatography coupled with mass spectrometer (UPLC-MS/MS). Plant growth was not suspended by the addition of NaCl in the NS, except for the plant height at the highest salinity level. In peppermint, the nutritional composition was not affected by the salinity, whereas it was significantly improved in spearmint as confirmed by the nitrate content decrease and the total antioxidant capacity, total soluble phenol, total carotenoid and essential oil content increases. Simultaneously, no effect of the salinity on essential oil or polyphenolic composition in both plants was induced. In conclusion, peppermint and spearmint production is feasible in the floating system even under mild salinity conditions, without negatively affecting either the crop yield or the plant's essential oil or phenolic composition. Indeed, low salinity levels improved the nutritional composition of spearmint plants.

Evaluation of the growth, drought tolerance and biochemical compositions of introduced red currant cultivars and Russian breeding genotypes in temperate continental climate

The aim of the work was to study the growth, drought tolerance and biochemical characteristics of introduced cultivars (‘Jonkheer van Tets’, ‘Hollandische Rote’ and ‘Viksne’) and some selected Russian cultivars and red currant genotypes (‘Shchedraya’, ‘Natali’, 129-21-61, 111-19-81, 261-65-19 and 271-58-24). The studies were conducted between 2014 and 2018 under temperate continental climate conditions. The intensity of transpiration was determined by using a torsion balance. The soluble solid concentration (SSS – % Brix) of the fruits was determined by using a digital refractomer. The content of the sum of sugars was determined by the weight method according to Bertrand's method. Ascorbic acid content was then determined by the iodometric method. The total phenolic content was determined by a colourimetric method. Climatic conditions were found to have significant influence on the disease severity of the red currant genotypes, while the infections caused by Sphaerotheca mors-uvae increased in optimum seasons and damages caused by Pseudopeziza ribis increased in drought seasons. None of the selected genotypes was found to be resistant to any of the diseases/pests, but ‘Jonkheer van Tets’, ‘Hollandische Rote’ and 111-19-81 were less affected by these diseases/pests. Weight, yield and raceme length of berries and the number of berries in a raceme were found to be higher in optimum seasons, and different cultivars/genotypes had superior characteristics for different parameters. The highest berry weight was observed in the 261-65-19 genotype (0.65 g), while the highest yield was noted in ‘Hollandische Rote’ (15.6 t · ha−1). It was also found that the water content of leaves and transpiration have a strong positive relationship with soil moisture at a depth of 0–200 mm but a week correlation with soil moisture at a depth of 200–400 mm. Results also showed that the transpiration of leaves decreases in later developmental stages (July). Hierarchical clustering suggested four clusters: the introduced cultivars produced one cluster, Russian cultivars are another cluster, 261-65-19, 111-19-81 and 129-21-61 genotypes make up a third cluster and the 271-58-24 genotype (superior in terms of phenolic contents) forms the fourth cluster.