Novel chitosan/alginate microcapsules simultaneously loaded with copper cations and Trichoderma viride have been prepared and characterized. Information about the intermolecular interactions between ...biopolymers and bioactive agents was obtained by Fourier transform infrared spectroscopy. Encapsulation of T. viride spores and the presence of copper cations in the same compartment does not inhibit their activity. Microcapsule loading capacity and efficiency as well as swelling behavior and release depend on both the size of the microcapsule and bioactive agents. The in vitro copper cation release profile was fitted to a Korsmeyer-Peppas empirical model. Fickian diffusion was found to be a rate-controlling mechanism of release from smaller microcapsules, whereas anomalous transport kinetics controlled release from larger microcapsules. The T. viride spore release profile exhibited exponential release over the initial lag time. The results obtained opened perspectives for the future use of chitosan/alginate microcapsules simultaneously loaded with biological and chemical agents in plant nutrition and protection.
Kinetics and mechanisms of copper cations and Trichoderma viride spores release from uncoated and chitosan coated alginate microcapsules were investigated. The gelation of a fixed amount of sodium ...alginate at different concentrations of copper ion solutions resulted in distinct kinetics and release mechanisms. The increase in copper cation concentration promoted, but the presence of the chitosan layer on the microcapsule surface and the increase in microcapsule size reduced the rate of active agent release. Fitting to simple Korsmeyer-Peppas empirical model revealed that the underlying release mechanism (Fickian diffusion or a combination of the diffusion and erosion mechanisms) depends on the copper cation concentration and presence of T. viride spores. The investigation pointed out that the proper selection of formulation variables helps in designing microcapsules with the desirable release of copper ions and T. viride for plant protection and nutrition.
The ascomycete fungus
causes early blight, one of economically the most important tomato diseases. Due to frequent use of fungicides,
has developed resistance with negative economic and environmental ...consequences. Research of new ways to control fungal pathogens has turned its eye to environmentally friendly chemicals with low toxicity such as boronic acids. The aim of our study was therefore to test the antifungal effects of phenylboronic and boric acid
on
.
. We isolated the pathogen from a symptomatic tomato plant and determined the minimum inhibitory concentration of phenylboronic and boric acid on
mycelial growth using the poisoned food technique. The antifungal effect was tested on a wide range of phenylboronic and boric acid concentrations (from 0.04 % to 0.3 %) applied separately to agar with mycelial disc of the pathogen. After five days of incubation, phenylboronic acid at low concentration (0.05 %) completely inhibited mycelial growth. Boric acid, in turn, did not significantly slow down mycelial growth but did reduce sporulation and confirmed its fungistatic effect. Our findings point to the potential use of phenylboronic acid to control phytopathogenic fungi. This is, to our knowledge, the first report on its antifungal effect on an agriculturally important pathogen
. Moreover, since
is also a human pathogen, these results may have clinical ramifications.
Finding a suitable alternative to the small pool of existing antifungal agents is a vital task in contemporary agriculture. Therefore, intensive research has been conducted globally to uncover ...environmentally friendly and efficient agents that can suppress pathogens resistant to the currently used antimycotics. Here, we tested the activity of boric acid (BA) and its derivative phenylboronic acid (PBA) in controlling the early blight symptoms in tomato plants infected with pathogenic fungus
. By following the appearance and intensity of the lesions on leaves of the tested plants, as well as by measuring four selected physiological factors that reflect plant health, we have shown that both BA and PBA act prophylactically on fungal infection. They did it by reducing the amount and severity of early blight symptoms, as well as by preventing deterioration of the physiological traits, occurring upon fungal inoculation. Phenylboronic acid was more efficient in suppressing the impact of
infection. Therefore, we conclude that BA, and even more so PBA, may be used as agents for controlling early blight on tomato plants, as they are both quite effective and environmentally friendly.
Bacterial SSB proteins, as well as their eukaryotic RPA analogues, are essential and ubiquitous. They avidly bind single-stranded DNA and regulate/coordinate its metabolism, hence enabling essential ...DNA processes such as replication, transcription, and repair. The prototypic
SSB protein is encoded by an
gene. Although the
gene promoters harbor an SOS box, multiple studies over several decades failed to elucidate whether
gene expression is inducible and SOS dependent. The SOS regulon is comprised of about 50 genes, whose transcription is coordinately induced under stress conditions. Using quantitative real-time PCR, we determined the
gene expression kinetics in UV- and γ-irradiated
and revealed that
gene expression is elevated in irradiated cells in an SOS-dependent manner. Additionally, the expression of the
gene was determined to indicate the extent of SOS induction. In a mutant with a constitutively induced SOS regulon, the
gene was overexpressed in the absence of DNA damage. Furthermore, we measured
gene expression by droplet digital PCR during unaffected bacterial growth and revealed that
gene expression was equal in wild-type and SOS
bacteria, whereas
expression was higher in the former. This study thus reveals a complex pattern of
gene expression, which under stress conditions depends on the SOS regulon, whereas during normal bacterial growth it is unlinked to SOS induction. The
gene is SOS regulated in such a way that its basal expression is relatively high and can be increased only through stronger SOS induction. The remarkable SOS induction observed in undisturbed wild-type cells may challenge our notion of the physiological role of the SOS response in bacteria.
Encapsulated bioactive agents applied to the Lactuca sativa L. present an innovative approach to stimulate the production of plant secondary metabolites increasing its nutritive value. Calcium and ...copper ions were encapsulated in biopolymeric microparticles (microspheres and microcapsules) either as single agents or in combination with biocontrol agents, Trichoderma viride spores, a fungal plant growth mediator. Both, calcium and copper ions are directly involved in the synthesis of plant secondary metabolites and alongside, Trichoderma viride can provide indirect stimulation and higher uptake of nutrients. All treatments with microparticles had a positive effect on the enhancement of plant secondary metabolites content in Lactuca sativa L. The highest increase of chlorophylls, antioxidant activity and phenolic was obtained by calcium-based microparticles in both, conventionally and hydroponically grown lettuces. Non-encapsulated fungus Trichoderma viride enhanced the synthesis of plant secondary metabolites only in hydroponics cultivation signifying the importance of its encapsulation. Encapsulation proved to be simple, sustainable and environmentally favorable for the production of lettuce with increased nutritional quality, which is lettuce fortified with important bioactive compounds.
Following identification of four viruses in a general survey of olive trees throughout Croatia, a detailed survey was conducted in 2009 in the field collection of the Institute of Agriculture and ...Tourism in Poreč (an important reservoir of Istrian native olive germplasm) in order to evaluate the sanitary status of the most important Croatian Istria olive cultivars. Twenty five samples from symptomatic or symptomless trees were collected from five autochthonous and four exotic cultivars. All the samples were tested by RT-PCR for the presence of: Olive leaf yellowing associated virus (OLYaV), Cherry leaf roll virus (CLRV), Strawberry latent ring spot virus (SLRSV), Arabis mosaic virus (ArMV), Olive latent virus-1 (OLV-1), Cucumber mosaic virus (CMV), Olive latent virus-2 (OLV-2) and Tobacco necrosis virus D (TNV-D). Six of the 25 plants were found positive to CLRV; all infected plants showed leaf and fruit deformation and leaf yellowing. Four positive samples were from the native cv. Buža whereas the other two were from two exotic cultivars: Ascolana tenera and Frantoio. The presence of CLRV, either in native or imported plants, highlights the importance of strict phytosanitary regulations to prevent incursion of key virus diseases.
Novel agroformulations for simultaneous delivery of chemical and biologically active agents to the plants were prepared by encapsulation of Trichoderma viride spores in calcium alginate microspheres. ...The impact of calcium ions concentration on the viability and sporulation of T. viride spores as well as on the microsphere important physicochemical properties were investigated. Intermolecular interactions in microspheres are complex including mainly hydrogen bonds and electrostatic interactions. T. viride germination inside matrix and germ tubes penetration out of microspheres revealed calcium alginate microspheres provide a supportive environment for T. viride growth. Differences in physicochemical properties and bioactive agents release behaviour from microspheres were ascribed to the changes in microsphere structure. Fitting to Korsmeyer- Peppas empirical model revealed the underlying T. viride release mechanism as anomalous transport kinetics (a combination of two diffusion mechanisms and the Type II transport (polymer swelling and relaxation of the polymeric matrix)). The increasing amount of T. viride spores in the surrounding medium is closely related to the release from microspheres and germination. The rate controlling mechanism of calcium release is Fickian diffusion. A decrease in the release rate with increasing calcium ion concentrations is in accordance with the calcium ions effect on the strength of the alginate network structure. T. viride germination inside microsphere diminished the amount of released calcium ions and slowed release kinetics in comparison with microspheres prepared without T. viride. The results indicated investigated agroformulations have a great potential to be used for plant protection and nutrition.
Plant pathogenic bacteria pose a significant threat to olive cultivation, leading to substantial economic losses and reduced yield. The efficacy of antimicrobial agents against these pathogens is of ...great interest for sustainable disease management strategies. As such, the management of olive knot disease is one of the major challenges in olive protection. In the presented study, through a series of in vitro assays, we investigated the antimicrobial effect of six essential oils (EOs) and their most concentrated constituents against causative agent of olive knot disease—Pseudomonas savastanoi pv. savastanoi, highlighting the high potential of Origanum compactum EO and its constituent carvacrol. Carvacrol exhibited the highest potential for practical application, demonstrating membrane disruption as its mechanism of action even at the lowest concentration. The bactericidal effect of antimicrobials was confirmed in a time–kill assay, where concentrations of MIC, 2× MIC, and 4× MIC were evaluated. Some of the applied treatments resulted in inhibition equal or higher than copper-based treatment. Additionally, we assessed the phytotoxicity of carvacrol by foliar application on olive cv. Leccino. The appearance of phytotoxic injuries majorly occurred on the young leaves of olive plants, with the highest proportion of damaged canopy observed when the 2× MIC concentration was applied. Due to its great efficiency against P. savastanoi pv. savastanoi in vitro, these findings highlight the potential of carvacrol as a molecule of interest for the development of environmentally friendly biopesticides. This study also contributes to the advancement of disease management practices in olive cultivation, leading to enhanced crop protection.
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