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Open access

Ismail Mohamed Helal

Abstract

This study aimed at investigating the antiviral activities of biocides made of formulated essential oils. These were derived from five plant species: fennel, oregano, peppermint, thyme and ginger. The potencies of these preparations were tested against local infection with the Tobacco necrosis virus (TNV) on common bean (Phaseolus vulgaris L.) and against systemic infection with the Cucumber mosaic virus (CMV) on cucumber (Cucumis sativus L.). After the determination of the most effective concentration, the formulated biocides were tested in protective and curative manners (before and after virus inoculation) against the growth of plants. The obtained results showed that the peppermint-derived biocide had the greatest effect on reducing the infectivity of the TNV virus (100% growth inhibition at 4000 ppm), whereas the biocide from thyme was the most effective against the infectivity of the CMV virus, as it induced a complete growth inhibition at 3000 ppm. The results of the protective and curative experiments revealed that the formulated biocides exerted high protection and curative effects against the two viruses. The observations revealed that the biocides were able to enhance plant defences against viral infection, as indicated by the increased levels of total chlorophyll, protein and phenols. Moreover, the levels of the oxidative stress markers including peroxidase (POD), polyphenol oxidase (PPO) and phenylalanine ammonia lyase (PAL) were improved compared to the control settings. In conclusion, the formulated biocides progressively present a favourable alternative to chemically synthesized pesticides in crop protection.

Open access

Anam Moosa, Shahbaz Talib Sahi, Sajid Aleem Khan and Aman Ullah Malik

Abstract

The ability of salicylic acid and jasmonic acid to suppress post-harvest infection with green mould Penicillium digitatum and blue mould P. italicum on three citrus species Citrus reticulata ‘Kinnow’, C. limon ‘Meyer Lemon’, and C. limetta ‘Mosambi’ was evaluated in a dose-response study. Salicylic acid (SA) and jasmonic acid (JA) were applied to the fruits as a post-harvest dip treatment followed by wound inoculation with the pathogens. Both resistance inducers caused a significantly lower disease severity compared with the infected but non-treated control, whereas disease incidence was not significantly lower than in the control. The efficacy of both SA and JA in reducing disease severity was concentration-dependent; the use of higher concentrations resulted in a greater degree of suppression. All the Citrus species tested in this study showed different responses in terms of disease development. C. limon ‘Meyer Lemon’ showed the highest disease development, and C. limetta ‘Mosambi’ the lowest. To get an insight into the mechanisms underlying the increase in resistance, the activity of defence-related enzymes – peroxidase (POD) and polyphenol oxidase (PPO) – was recorded in SA- and JA-treated fruit peelings. The activity of both enzymes was directly proportional to the concentration of the SA and JA applications. The highest activity of PPO and POD was observed in C. reticulata ‘Kinnow’ and the lowest in C. limon ‘Meyer Lemon’ fruits. This study is the first to document an increase in the activity of PPO and POD in SA- and JA-treated Citrus species in the presence of blue mould and green mould pathogens.

Open access

Tomoki Hattori, Yang Chen, Shinichi Enoki, Daisuke Igarashi and Shunji Suzuki

Abstract

Berry skin colour is a crucial determinant of red/black grape berry quality. We investigated the effects of combination treatments with amino acids and a low concentration of ABA on anthocyanin accumulation in grapes. Among the amino acids tested, isoleucine and phenylalanine resulted in high anthocyanin contents in grape cell cultures. The combination treatments with isoleucine or phenylalanine, and a low concentration of ABA enhanced anthocyanin accumulation in grape cells and detached grape berries. The combination treatment with isoleucine, but not with phenylalanine, and ABA upregulated MybA1 expression. Field-grown grapevines received combination treatments with isoleucine or phenylalanine, and ABA in two growing seasons. In the 2015 growing season, the combination treatments with isoleucine or phenylalanine, and a low concentration of ABA accelerated anthocyanin accumulation in grape berry skins of field-grown grapevines on days 10 and 31 post treatment. The effects on anthocyanin accumulation became negligible at harvest. The effect of the combination treatment with phenylalanine and a low concentration of ABA on anthocyanin accumulation was masked in the 2017 growing season due to the unexpected stimulation of anthocyanin accumulation by the low concentration of ABA, although the combination treatment accelerated anthocyanin accumulation on days 3 and 10 post treatment. Taken together, the results suggested that exogenous isoleucine and phenylalanine interacted with ABA-mediated anthocyanin accumulation in grape berry skins of field-grown grapevines when the activity of ABA used to treat the grapevines was inadequate.

Open access

Larona Keabetswe, Guang Cheng Shao, Jintao Cui, Jia Lu and Tebogo Stimela

Abstract

Quality of fresh produce is the most critical issue in the economics of a vegetable enterprise. In order to investigate the effect of biochar amendment and deficit irrigation on tomato fruit quality, experimental research was conducted under a rain shelter in southern China during the 2017 and 2018 growing seasons. The experiment consisted of five treatments. Crops were irrigated to 100% of field water capacity at all growth stages as treatments T1 and T2. The other treatments received 30% less irrigation water than T2 when its soil water content reached 70% of field capacity, and were designated as treatments T3, T4 and T5, applied at the vegetative (stage I), flowering and fruit development (stage II), and fruit ripening (stage III) stages, respectively. Treatment T1 included no biochar, while the other treatments included 10% biochar by weight. The results showed that the total soluble solids (TSS) content, sugar-to-acid ratio (SAR), vitamin C (VC) content, and colour index (CI) increased in the deficit irrigation treatments depending on the phenological stage, the fruit ripening stage in particular. Meanwhile, single fruit weight was significantly (p > 0.05) reduced by water deficit at stages II and III, subsequently affecting the total fruit yield. Biochar improved soil moisture conservation and had a positive effect on fruit quality as evidenced by better single quality attributes (p > 0.05) of T2 over T1. The GRA and TOPSIS appraisal methods were used to conduct the comprehensive quality analysis. Eventually, treatment T5 ranked the best in both seasons, and this was also confirmed by the combinational evaluation method.

Open access

Eva Maria Prem, Nadine Praeg, Katrin Hofmann, Andreas Otto Wagner and Paul Illmer

Summary

Five differently developed soils aged 6, 35, 80, 150, and >5000 years with the same bedrock and the same (current) climate conditions were chosen to assess abiotic and enzymatic properties as well as methanogenic and methanotrophic activities. Most abiotic properties (dry weight, pH, soil organic matter, and ammonium content), enzyme activities (dehydrogenase [DH] activity, ammonification [AM] rate, dimethylsulfoxide reduction), and potential methane oxidation (PoMO) per gram of dry weight (DW) increased with soil age. In contrast, potential methane production (PoMP) as well as the nitrate content per gram of DW and most enzymatic properties per gram of soil organic matter (SOM) did not increase with soil age but reached its maximum in the middle-aged soils (80–150 years). Our results show that (i) microbial activity does not consequently increase with SOM content/soil age; (ii) methane production can be measured in undeveloped soils, whereas methane oxidation is more restricted to fully developed soils; and (iii) certain soil modifications (change in water content, ammonium addition) could influence potential methane production/oxidation. When considering the concurrent release of raw soil because of the melting of perpetual ice, these data could help to better understand and assess the consequences of global change.

Open access

Anna Lenart-Boroń, Tadeusz Zając, Piotr Mateusz Boroń and Agnieszka Klimek-Kopyra

Summary

The bacterial nodulation (nod) genes are essential in the formation process of root nodules. This study was aimed to verify the occurrence of nodule-associated bacteria in two pea varieties (“Tarchalska” and “Klif ”) inoculated with Rhizobium inoculants – Nitragine™ and a noncommercial one produced by the Polish Institute of Soil Science and Plant Cultivation (IUNG). The number of colonies isolated on yeast extract mannitol (YEM) agar from the nodules of “Klif ” inoculated with IUNG inoculants was significantly higher than the number of colonies isolated from other variants. Species identification was based on sequencing of 16S rDNA, which revealed that despite careful sterilization of nodules, sequences of other bacterial species were detected. Among them, one sequence belonged to Rhizobium leguminosarum (isolated from IUNG inoculant). To assess the presence of nodulation-capable Rhizobium, amplification of the nodC gene was performed, which revealed that of 29 samples, 19 were positive. The remaining isolates, including reference strain and bacteria isolated from Nitragine™, lacked this gene. The results show that pea nodules harbor a very diverse community of bacteria. The lack of nodC gene in some strains isolated from plants inoculated with Nitragine™ and with IUNG inoculant proves that even if R. leguminosarum are abundant, they may not be efficient in nodulation.

Open access

Giovanni Peratoner and Erich M. Pötsch

Summary

In terms of botanical composition, grassland vegetation in experimental plots and field studies can be described by means of different parameters (plant density, cover, frequency or yield proportion). Each parameter describes different features, which under certain circumstances may be correlated one to each other to some extent, but are not fully equivalent. The choice of the parameter to be assessed depends therefore, in first instance, on the specific aim of the investigation. For the assessment of the chosen parameter, many methods are available that differ from each other in terms of subjectivity, precision, effort and requirement for technical equipment. The choice of method depends mainly on the required precision, the affordable effort and on the available resources.

Open access

Amrei Voelkner, Charlotte Diercks and Rainer Horn

Summary

Digestates and compost are used as valuable fertilizers in agriculture because of their benefits for plant nutrition and carbon sequestration potential. These amendments are also suspected to interfere negatively with the soil. To compare their relevance for priming effect and hydrophobicity of soils, two amounts of digestate or compost, respectively, were mixed with a homogenized cambic Luvisol and a Podzol. The basal respiration rate (BAS), the repellency index (RI) and organic carbon content (Corg) of pre-dried mixtures were investigated. The podsolic mixture showed quantitative reduction of Corg and increased BAS (this effect was not statistically significant) due to priming effect through microbial stimulation. As a result of enhanced organic substance (OS) protection in the cambic Luvisol mixture, constant amounts of Corg and declined BAS could be detected. The wettability was reduced in both soils: either directly by the supply of amphiphilic components or indirectly by increased incorporation of microbial exudates. This reduction was not statistically significant. Higher contents of available organic compounds in digestates and higher amounts of hydrophobic humic acids in the compost could be assumed to be decisive for generation of hydrophobicity. Also the soil texture controlled the microbial decomposition by higher incorporation of OS in finer pores and contributed to the protection against microbial decay.

Open access

Anneka Mordhorst, Heiner Fleige, Iris Zimmermann, Bernd Burbaum, Marek Filipinski, Eckhard Cordsen and Rainer Horn

Zusammenfassung

Gegenwärtig diskutierte Phänomene, wie häufig auftretender Oberflächenabfluss, vermehrte Bodenerosion und verringerte Ertragssicherheit, lassen sich ansatzweise über Bodenstruktureigenschaften und eine daraus hervorgehende, räumlich unterschiedlich gesättigte Wasserleitfähigkeit des Bodens erklären. Hierzu wurden Datensätze aus 766 Profilen unter Acker- und Grünlandnutzung in den vier Hauptnaturräumen Schleswig Holsteins (Östliches Hügelland, Niedere und Hohe Geest sowie Marsch) zur gesättigten Wasserleitfähigkeit (kf) in vertikaler und horizontaler Richtung und damit deren Richtungsabhängigkeit (Anisotropie) bis in eine Tiefe von 60 cm untersucht. Die Ergebnisse zeigen eine verstärkte Anisotropie der kf in horizontaler Richtung an, die jedoch in Abhängigkeit vom geologischen Ausgangsgestein, Bodentyp und Tongehalt sowie von der Landnutzung variiert. Unter Ackernutzung weisen die Unterböden aller Hauptnaturräume im Mittel eine horizontale Anisotropie auf, die unterhalb der Pflugsohle (≤ 40 cm Tiefe) am stärksten ausgeprägt ist und auf Plattenstrukturbildungen als Folge der Bodenbewirtschaftung hindeuten. Unter Grünlandnutzung zeigen besonders die Oberböden eine horizontale Anisotropie, wobei diese in den beiden Geestregionen mit einem hohen Anteil an Viehwirtschaft auch im Unterboden sehr ausgeprägt ist. Anisotropieeffekte, insbesondere im Unterboden unter Ackernutzung, deuten sich auch bodentypspezifisch für Kolluvisole, Pseudogley-Parabraunerden und Pseudogleye an. Deren hohe Empfindlichkeit gegenüber anthropogenen Strukturänderungen (Plattenbildung) spiegelt sich im zeitlichen Verlauf der horizontalen kf wider, die über die letzten 30 Jahre im Östlichen Hügelland signifikant zugenommen hat.

Open access

Antoni F. Tulla

Abstract

In a peripheral rural area like the Pyrenees, it is necessary to promote local resources, which can be converted in value-added activities with comparative advantages in relation with other areas. The Comparative Advantage Theory and Second-Best Option (SBO) methodology are presented here. Each local territory can develop activities or services, even though there are other places that may be more suitable for them, when these are the best specialization option for this territory. The idea of SBO methodology means engaging in activities that make it possible to achieve a comparative advantage. Four cases are discussed: a) transformation of dairy products into competitive value-added commodities; b) promotion of extensive cattle farming based on local natural grass feed; c) development of value-added tourist activities linked to local landscape; and d) planning value-added cultural activities related with cultural heritage.