POD) And Polyphenoloxidase Research Articles

Plant-Programmed Cell Death-Associated Genes Participation in Pinus sylvestris L. Trunk Tissue Formation.

Molecular genetic markers of various PCD (programmed cell death) variants during xylo- and phloemogenesis have been identified for the first time in Scots pine under lingonberry pine forest conditions in Northwest Russia (middle taiga subzone). PCD is a genetically determined process. Gene profiles of serine and cysteine proteases (endopeptidases), endonucleases, and metacaspases families are often considered markers of the final xylogenesis stage. In the present study, we examined the gene expression profiles of the BFN (bifunctional endonuclease) family-BFN, BFN1, BFN2, BFN3, and peptidase (cysteine endopeptidase, CEP and metacaspase, MC5) in the radial row, in addition to the vascular phloem and cambium (F1), differentiating xylem (F2), sapwood (SW), and transition zone during the active cambial growth period of uneven-aged pine trees (25-, 63- and 164-cambial age (c.a.) years old). We have shown that the expression patterns of the PCD-related genes did not depend on the cambial age but were largely determined by plant tissue type. In the radial row F1-F2-SW, we studied the activities of enzymes, including sucrose in metabolism (sucrose synthase, three forms of invertase); antioxidant system (AOS) enzymes (superoxide dismutase, catalase); and peroxidase andpolyphenol oxidase, which belonged to AOS enzymes and were involved in the synthesis of phenolic components of cell walls. The activity of the enzymes indicated that the trunk tissues of pine trees had varying metabolic status. Molecular genetic PCD regulation mechanisms during xylem vascular and mechanical element formation and parenchyma cells' PCD during the formation of Scots pine heartwood were discussed.

Insight into peroxidase and polyphenol oxidase mimic activity of spinel ferrite nanoparticles and their GO composites

Present work reports the comparative evaluation of MFe2O4 (M = Mn, Co and Cu) nanoparticles (NPs), graphene oxide (GO) and their nanocomposite (NC) for their intrinsic peroxidase and polyphenol oxidase (PPO) mimic activity of followed by the catalytic sensing of H2O2. Pure and doped MFe2O4 NPs were screened initially for peroxidase and PPO mimic activity. Among the tested metal ferrite NPs, MnFe2O4 NPs showed the highest enzyme mimic activity for both the enzymes. Thus, MnFe2O4-GO NC was synthesized by the facile ultrasonication method and characterized using FT-IR and XRD techniques. TEM micrographs of NC showed that MnFe2O4 NPs were anchored on GO sheets with lesser agglomeration than bare ferrite NPs. SEM-EDX confirmed the presence of MnFe2O4 and GO in NC. The greater surface area of NC as compared to pristine NPs was confirmed from BET analysis. MnFe2O4 NPs displayed highest peroxidase and PPO mimic activity followed by NC and GO. The results were correlated with the facile inter-conversion of Mn2+-Mn3+ ions. Thus, ease of inter-conversion of oxidation state was the dominating factor of highest activity of MnFe2O4 NPs rather than the surface area. The colorimetric detection of H2O2 was also achieved in the range 0.2 mM–1.0 mM H2O2. In-situ trapping experiments confirmed that OH. radicals were major active species involved in peroxidase mimic activity. The reaction mechanisms for both the reactions were proposed. Kinetic studies were performed and data was analysed using Michaelis Menten equation. The values of Vmax and Km for both the reactions proved MnFe2O4 NPs as potential oxidase mimic for a wide range of potential applications.

Effect of thermosonication on enzymatic oxidation and physicochemical properties of soursop (Annona muricata) pulp

Soursop is an exotic tropical fruit, highly perishable, presents losses around 30% in postharvest, has marked commercial importance especially for internal consumption and a maximum shelf life. The objective of the present work was to study the effect of thermosonication (TS) on some physicochemical properties and the enzymatic oxidation of soursop pulp. The thermosonication treatments used on the samples were at 40 kHz, in a temperature range between 20-60 ºC, for 25 minutes. The soluble solids, pH, vitamin C concentration, inactivation of peroxidase (POD) and polyphenoloxidase (PPO) in the soursop pulp were evaluated before and after the treatments. The results indicate a loss of vitamin C was observed in a 2.63; 13.16 and 28.95% for temperatures at 20, 40 and 60 ºC, respectively. On the other hand, a partial inactivation of the enzymes, POD, in 48.41; 69.83 and 74.24% and for PPO in 56.38; 74.47 and 81.91% was achieved at temperatures at 20, 40 and 60 ºC respectively. Finally, it was demonstrated that the US combined with heat (TS) inactivates in a large percentage the POD and PPO enzymes in the soursop pulp needing less heat, which could make it more efficient in comparison with the thermal treatments. Highlights Ultrasound combined with heat (TS) can inactivate POD and PPO enzymes in the soursop pulp, achieving considerable retention of vitamin C. Peroxidase (POD) and Polyphenoloxidase (PPO) trigger enzymatic processes affecting product natural color. Soursop is an exotic fruit with high levels of bioactive compounds, and great agro-industrial potential given its high recovery yields and excellent sensory characteristics. A vitamin C retention level of 71.05- to 86.84% was achieved in soursop pulps that have undergone thermosonification.

Storage of markies cultivar potatoes for prossessing

The refrigerated induce the sweetening of the potato, which results in the dark color. The objective of this study was to determine the temperature and shelf life of Markies potato tubers under refrigerated storage for the processing of French fries. The levels of total soluble sugar (TSS), reducing sugars (RS), peroxidase (POD) and polyphenoloxidase (PPO) activity, color after frying and start of sprout were determined. The accumulation of TSS started at 30 days in the tubers at 4 and 5 °C and in the tubers at 6 and 8 °C, at 150 days. The activity of POD and PPO were not influenced by temperature or storage time. Tubers at 4 e 5 °C showed higher TSS and RS contents and darker color after frying than tubers stored at 6 and 8 °C which had their color maintained within the industry-acceptable standard up to 240 days of storage. Temperatures of 4 and 5 °C delayed the onset of sprouting, starting at 150 days, and at temperatures of 6 and 8 °C, the onset of sprouting occurred from 90 and 60 days of storage, respectively. It is concluded that the cultivar Markies should be stored at 6 °C for 240 days.

Effect of storage temperature and time on potato cv. Innovator industrial quality

Reducing the storage temperature delays sprouting and increases the storage period, prolonging the supply to the industry. However, it may cause enzymatic browning before frying and non-enzymatic browning over frying. Therefore, the objective of this study was to determine the effects of a reduction in the temperature and storage time on the quality of cv. Innovator intended for frying. Potato tubers were stored at 6, 7 and 8 °C for 150 days. This study analyzed the total soluble sugars (TSS), non-reducing sugars (NRS), reducing sugars (RS), post-frying coloring, fresh mass loss (FML), sprouting onset, peroxidase (POD) and polyphenoloxidase (PPO) activity. The TSS, NRS and RS contents were higher in tubers stored at 6 °C, classified in category 3, while at 7 and 8 °C, it was classified in category 2. Storage time affected sugar concentrations only in tubers at 6 °C. Also at 6 °C, the FML was lower and sprouting was delayed by 30 days. Regardless of temperature and storage time, there was no enzymatic darkening due to POD and PPO activity. It is concluded that reducing the storage temperature to 6 °C prolongs the dormancy period, reduces fresh mass loss, increases reducing sugar content and non-enzymatic browning.

Characterization of Partial Resistance to Bean Rust Disease caused by Uromyces appendiculatus in Seven Common bean Varieties

Partial resistance (PR) to bean rust (Uromyces appendiculatus) in seven bean varieties was determined through three epidemiological parameters, final rust severity (FRS %), area under disease progress curve (AUDPC) and rate of disease increase (r-value) at adult plant stage under natural infection in open field, and four components of resistance (incubation period, latent periods, infection frequency and Pustule size under artificial inoculation in greenhouse) at seedling stage under artificial inoculation in greenhouse. Resistance parameters under both field and greenhouse conditions were varied significantly among bean varieties tested in different years. Montcalm, Nebraska and Bronco were classified partially resistant varieties with decreasing the amount of rust infection and disease development, whereas Karnak, Giza 6, Paulista and Contender were exhibited fast-rusting varieties based on both open field and greenhouse experiments. The partially resistant varieties had higher amounts of three enzymes catalase (CAT), peroxidase (POX) and polyphenoloxidase (PPO) compared with fast-rusting varieties. High significant correlations (r2) were observed among resistance parameters in both field and greenhouse experiments. Correlation matrix suggests that AUDPC and LP50 were good and more reliable parameters for evaluation and selection for resistance to bean rust.

A case study of non-traditional treatments for the control of wheat stem rust disease

Wheat stem rust causes by Puccinia graminis f. sp. tritici is a serious threat to wheat production all over the world. This study evaluated the efficacy of Bacillus subtilis, B. polymyxa and B. megaterium, Eugenol and leaf extract of Artemisia cina against the disease, and the involved mechanisms in disease resistance. B. subtilis and Eugenol treatments inhibited spore germination and increased incubation and latent periods than other treatments. Additionally, the lowest infection type, pustule length and pustule width, and receptivity (no. of pustules) were recorded in case of B. subtilis and Eugenol treatments compared with the check control. The best results in disease assessment were achieved by foliar spray application 24 h before and after inoculation. Abnormalities, lysis, collapse, and shrinking of urediniospores were recorded in treated leaves. The activities of antioxidant defense enzymes, i.e., catalase (CAT), peroxidase (POX), and polyphenoloxidase (PPO), were significantly increased in B. subtilis and Eugenol treatments. On the other hand, electrolyte leakage was decreased. The active compounds in B. subtilis were revealed by utilizing GC-MS analysis.

Bio-Control of Chamomile Powdery Mildew Using Cyanobacteria and Some Antagonistic Microorganisms

Field experiments were carried out under natural infection in the Experimental Farm of Sids Agricultural Research Station, Agric. Res. Center, Beni-Sweif governorate to evaluate the potentiality of Bacillus subtilis, Pseudomonas fluorescens, Trichoderma harzianum and cyanobacteria (Spirulina platensis)alone or in mixture to control powdery mildew on chamomile and its productivity using two application methods: soaking the seedling roots before transplanting + foliar spray and foliar spray only. Generally, all the tested bioagents were effective in reduction the disease incidence and severity leading to a significant increase in fresh and dry weights of the blossoms as well as essential oil percent and oil yield compared with the control treatment. Soaking the chamomile seedling roots and spraying the leaves with suspensions for bioagents tested were the most effective in reducing the disease incidence and severity than spraying the leaves by the suspensions only. Mixing the cyanobacteria (S. platensis) with the fungal and bacterial antagonistics was more effective compared to each treatment separately. The highest efficacy was obtained from plots received mixed treatment of S. platensis + P. fluorescens in addition to the fungicide Topas 100 EC. Furthermore, all the treatments showed significant increases in the defence-related enzymes, peroxidase (PO) and polyphenoloxidase (PPO) as compared with the untreated control. Spirulina platensis significantly enhanced the growth of T. harzianum and did not show any inhibitory effect against bacterial growth as well as significantly increased the number of bacterial colony forming units (cfu) of B. subtilis and P. fluorescens which significantly improved the microbial status in the rhizosphere of chamomile plants.

EFFICACY OF SOME BIOCONTROL ORGANISMS, ANIMAL MANURES AND FUNGICIDES ON CONTROLLING OF POTATO BLACK SCURF AND STEM CANKER DISEASE

In the last few years, stem canker and black scurf disease caused by Rhizoctonia solani Kuhn (teleomorph Thanathephorus cucumeris [Frank] Donk) are among different diseases important attacked potato crop under the Egyptian climate conditions. Eight fungal isolates were isolated from diseased plants representing different localities in different governorates i.e. El-Kassasen (Ismailia Gov.), Kafer El-zayat (Gharbia Gov.), El-Katatba (Minofya Gov.), Housh-Essa (Behera Gov.), El-Badrashen (Giza Gov.), Behdal (Minia Gov.), Dairoot (Assiut Gov.) and Shandaweel (Sohag Gov.). The obtained isolates differed in their culture color, number and size of sclerotia. Isolates which isolated from El-Kassasen, Kafer El-zayat, El-Khatatba, El-Badrashen and Behdal, were belonging to AG-3 anastomosis group. Under greenhouse conditions this isolates were tested for their pathogenicity to potato (Lady-Roseta cv.), during summer growing season 2015 and gave high rates of infection to potato plants. In this manner, the isolate which obtained from El-Badrashen (Giza Gov) was the highest aggressive one and causing the highest percentage of stem canker and black scurf. In separate experiments under greenhouse conditions, a number of biocontrol organisms,animal manure extracts and fungicides were evaluated alone in their efficacy to reduce the infection of potato stem canker and black scurf diseases.With regard to bioagents test, Trichoderma harzianum at concentrate 2.0% improving percentages of eyes germination and reduce dead sprouts of potato and decrease of stem canker and black scurf incidence, compared with Bacillus subtilis and algae treatments. While, animal manure test, Pigeons extract at concentrate 2.0%, gave the highest effect on reducing of stem canker and black scurf incidence compared to Chicken extract. In fungicides experiment, Rizolex (Tolchlophos-methyl) when used before soil inoculation give the best effect in reducing of non-germinated eye, dead sprouts and incidence of stem canker and black scurf compared to Monceren (Pencycuron). On the other hand, the effect of different treatments on the content of potato plants of phenols and oxidative enzymes were studied. In this respect T. harzianum, gave the highest content of phenols and activities of oxidative enzymes Peroxidase (PO) and Polyphenoloxidase (PPO).

Necrotrophic fungus Macrophomina phaseolina tolerates chromium stress through regulating antioxidant enzymes and genes expression (MSN1 and MT).

Cr(VI) tolerance level of phytopathogenic fungus viz., Macrophomina phaseolina (Tassi) Goid was assessed through growth, morphological, physiological, and metal accumulation assays. Initially, the fungus growth assays indicated that the fungus can grow over concentration range of 20-3000ppm and exhibited high tolerance index (0.88-1.00) and minimum inhibitory concentration at 3500ppm of Cr. Observations under compound and scanning electron microscope un-revealed the structural features of hyphae under Cr stress as thick-walled,aggregated, branched, short and broken, along with attachment of irregular objects on them. Metal accumulation analysis revealed reduction in Cr(VI) accumulation by the fungus with increase in metal concentration in the growth medium (500-3000ppm). Cr stress induced upregulation of antioxidant enzyme activities (catalase, peroxidase andpolyphenol oxidase), expression of genes (MSN1 and metallothionein) and appearnace ofnew protein bands suggesting the possible role in protection and survival of M. phaseolina against Cr(VI)-induced oxidative stress. This study concludes that interference of Cr with growth and physiological process of M. phaseolina could affect its infection level on its host plant, therefore, synergistic action of two factors needs to be addressed, which may aid to guide future research efforts in understanding impact of plant-pathogen-heavy metal interaction.

Management of Faba Bean Rust by Some Antagonistic Bioagents and Induced Resistance Chemicals

Eight bacterial and fungal isolates as well as four induced resistance chemicals (IRCs) were assessed <i>in vitro</i> and <i>in vivo</i> against <i>Uromyces viciae</i> –<i>fabae</i> (Pers.) Schroet, the causal of faba bean rust. The inhibitory effect of <i>Bacillus</i> spp. was ranged between 35.2-50.4%, <i>Trichoderma</i> spp. between 39.0-59.0%. and IRCs between 34.3- 57.7%. In addition, the highest inhibitory effect on the germinated urediospores of the causal fungus was obtained by <i>B. subtilis, T. viride</i> and bion (BTH). Under greenhouse conditions, spraying faba bean plants with any of the tested bioagents significantly reduced disease severity and increased the produced pod yield compared with the control treatment. Also, spraying plants grown from soaked seeds for 12 hrs before sowing in any of the IRCs or soaking in water only with any of these inducers significantly reduced disease severity and increased the produced pod yield compared with the control treatment. Field experiments during two successive seasons under the natural infection by <i>faba bean</i> rust at Behera governorate revealed that spraying <i>B. subtilis</i> and <i>T. viride</i>, each alone or in combination, on plants grown from soaked seeds in BTH at beginning of the incidence of the disease significantly reduced disease severity and increased the produced seed yield compared with the control. On the other hand, plants sprayed with the mixture of both bioagents were of the lowest infection and produced the highest dry seeds/plot compared with the other treatments and the control. However, the fungicide Topas was the superior treatment for lowering disease severity and increasing the produced seeds yield. Considerable increase in the activity of three oxidative- reductive enzymes, <i>i.e</i> phenyl alanine ammonia lyase (PAL), peroxidase (PO) and polyphenoloxidase (PPO) in the leaves of all treatments compared with both control treatments. Furthermore, plants grown from seeds soaked in BTH showed the highest activity of the three enzymes followed by those sprayed with <i>B.subtilis</i> then with <i>T.viride</i>.

Changes in bioactive compounds in spiny coriander leaves in response to inflorescence pruning at different growth stages

The objective of the study was to evaluate the effect of inflorescence pruning on spiny coriander and determine the levels of antioxidants at different growth stages. Inflorescence pruning increased leaf biomass by 188%, although total biomass did not vary among treatments. Pruning altered the biomass partition, induced the earmarking of a higher percentage of photosynthates for the production of new leaves, and increased the leaf contents of reducing sugars, sucrose and soluble proteins. The contents of bioactive compounds and antioxidant activity were not affected by inflorescence pruning. Regarding the growth stages, the polyphenol and flavonoid contents were high during the juvenile stage, and highest levels of carotenoids, chlorophyll a and chlorophyll b were produced at the beginning of plant maturation. From the full maturity stage onwards, peroxidase (POD) and polyphenoloxidase (PPO) were highest, coinciding with a decrease in bioactive compounds. Considering the production of bioactive compounds and antioxidant, POD and PPO activities, the ideal harvesting time would be in the late juvenile and early maturation stages of spiny coriander, between 90 and 120 days after germination. Moreover, inflorescence pruning is recommendable for spiny coriander cultivation, for increasing the leaf biomass without affecting the leaf levels of bioactive compounds and antioxidant activity. Our results highlight the relevance of the growth stages for the production of bioactive compounds of this crop, contributing to improve the cultivation practices, with higher yields and an optimized use of the therapeutic properties of the leaves.

Effects of high hydrostatic pressure, dense phase carbon dioxide, and thermal processing on the quality of Hami melon juice

AbstractThis article investigates how high hydrostatic pressure (HHP; 400 MPa, 45 °C, 10 min), dense phase carbon dioxide (DPCD; 30 MPa, 65 °C, 15 min), and thermal processing (TP; 85 °C, 10 min) affect the quality of Hami melon juice in storage. After HHP treatment, the total plate counts, yeasts, and molds were undetectable during storage (28 days) while microorganisms were observed at 14 and 21 days in DPCD‐ and TP‐treated samples, respectively. It seems that the total soluble solids (TSS) and the color parameters, that is, a*, b*, and L* were less affected by different processing methods. However, the activity of lipoxygenase (LOX), peroxidase (POD), and polyphenoloxidase (PPO) remarkably decreased after TP, whereas residual activities of these three enzymes (&gt;70%) were detected after HHP treatment. The glucose and fructose of Hami melon juice remained at the same level after HHP treatment, while sucrose decreased in HHP‐treated juice. Additionally, the reduction of organic acids after HHP treatment was less than that after TP. In general, the overall quality of Hami melon juice after HHP treatment was much better than that of the TP‐ and DPCD‐treated juice, suggesting that HHP treatment could be an optimal way to maintain the quality of Hami melon juice.Practical applicationFrom this work, the effects of three different treatments (HHP, DPCD, TP) on the microorganisms, enzyme activities, sugars, organic acids and sensory quality of Hami melon juice was studied, and HHP showed the great potential. Thus, it can be optional new techniques for the industrial production of Hami melon juice.

Antioxidative responses of Nostoc ellipsosporum and Nostoc piscinale to salt stress

The responses of the cyanobacteria Nostoc ellipsosporum and Nostoc piscinale to salt stress during various growth stages were studied. Nostoc ellipsosporum was more NaCl tolerant and attained more biomass under salinity than N. piscinale. Accumulation of proline was detected in N. ellipsosporum under salinity stress. Malondialdehyde content decreased in both species on day 9 (mid log phase) under salt stress. A similar trend was detected in hydrogen peroxide (H2O2) content in N. ellipsosporum. Strong induction in catalase (CAT) activity was observed in N. ellipsosporum on day 9 in the presence of salt. The increase in CAT activity of N. piscinale was observed only at higher concentrations of NaCl. In contrast to N. ellipsosporum, induction in peroxidase and polyphenol oxidase (PPO) activities on day 9 was stronger in N. piscinale. Salinity enhanced superoxide dismutase (SOD) and PPO activity in N. ellipsosporum at all growth stages. Moreover, different isoforms of CAT and SOD were detected in these cyanobacteria. Apparently, selection pressure in these cyanobacteria has led to the evolution of SODs and CATs as the main antioxidant enzymes against reactive oxygen species. Phycobiliprotein content in N. ellipsosporum under all conditions was significantly higher than that in N. piscinale. NaCl at moderate concentrations significantly increased phycobiliprotein content in the middle of the log phase in both species. Moreover, contrary to N. piscinale, the size of phycobilisomes [phycoerythrin + phycocyanin / allophycocyanin] in N. ellipsosporum increased significantly under salt stress at the mid of log phase and later. The increase in size of phycobilisomes in N. ellipsosporum could help this species to withstand salt stress by enhancing energy transfer capacity. These results suggest that N. ellipsosporum cells could be better protected against salinity-induced oxidative damage by maintaining higher levels of antioxidative enzymes, proline, and phycobiliproteins than the cells of N. piscinale.

Effect of honey and calcium dips on quality of fresh-cut nectarine (Prunus persica L. Batsch)

The effects of calcium chloride (CaCl2) and honey dips were investigated on the quality of fresh-cut nectarines. Nectarine fruit samples at the commercially ripe stage were wedged and then dipped in distilled water, 50% honey, 1% CaCl2 or 1% CaCl2 combined with 50% honey solutions, followed by storage at 4 ± 0.5 °C and 90 ± 2% relative humidity for 7 d. The following parameters were investigated during storage: firmness, total soluble solids (TSS), superficial color, color darkening score and index, total phenols content and the enzyme activities of peroxidase and polyphenol oxidase (PPO). CaCl2 and CaCl2 + honey solution dips improved the texture and maintained the TSS content. Honey and CaCl2 + honey suppressed an increase in the color difference. Minor changes were found in color attributes (lightness (L*), hue and chroma values), color darkening, total phenols content and PPO activity during storage. CaCl2 + honey maintained the quality of the nectarines by delaying color change and firmness loss.

Effect of High Hydrostatic Pressure and Temperature on Enzymatic Activity and Quality Attributes in Mango Puree Varieties (cv. Tommy Atkins and Manila)

Pectinmethylesterase (PME), peroxidase (POD), and polyphenoloxidase (PPO) residual activities (RAs) and physicochemical parameters (pH, total soluble solids (TSS), water activity (aw), viscosity and color) of Tommy Atkins and Manila mango purees (MPs) were evaluated after high hydrostatic pressure (HHP) treatments at 400–550 MPa/0–16 min/34 and 59 °C. HHP treatment applied at 59 °C induced higher enzyme inactivation levels than the treatment applied at 34 °C in both MPs. The lowest RA of PME (26.9–38.6%) and POD (44.7–53%) was achieved in Manila MP treated at 450 MPa/8–16 min/59 °C and 550 MPa/4–16 min/59 °C, respectively. Otherwise, Tommy Atkins puree pressurized at 550 MPa/8–16 min/59 °C had the lowest PPO RA (28.4–34%). A slight decrease in pH and TSS values of both HHP-processed MPs at 34 and 59 °C was observed, whereas the aw remained constant after processing. The viscosity of MPs tended to augment up to 2.1 times due to the application of HHP. No significant changes were observed in color parameters of Tommy Atkins MP, except at 550 MPa and 59 °C where higher yellow index (YI) (122.4 ± 3.3) and lower L* (37.3 ± 5.3) were obtained compared to the untreated MP. HHP caused an increase in L* values in Manila MP, whereas no clear trend was observed in YI. HHP processing at 550 MPa combined with mild temperature (59 °C) during 8 min could be a feasible treatment to reduce enzymatic activity and preserve fresh-like quality attributes in MP.

Elicitation of plant defense enzymes against Fusarium oxysporum f. sp. lycopersici in tomato plant using a novel rhizobacteria Providencia rettgeri MSS2

Abstract Providencia rettgeri MSS2, a novel gamma proteobacterium, isolated from the rhizospheric soil of tomato plant in Gujarat, India has in vitro biocontrol activity against Fusarium oxysporum f. sp. lycopersici (FOL), causative agent of fusarium wilt in tomato plant. It also has a strong root colonization potential which was confirmed by SEM analysis. Talc-based bioformulation of MSS2 was applied under pot trials to study the mechanism of induced resistance against FOL by enhancement of defense enzymes and total phenolics in tomato. Results of the study showed an increase in the defense enzymes like peroxidase (PO) and polyphenoloxidase (PPO), maximum increase of these enzymes was observed on the 6th day of pathogen challenge. Enzyme activity was found to be increased by 1.2 fold in the plants pretreated with MSS2 and challenged with FOL as compared to only pathogen treated plants. Activity of phenylalanine ammonium lyase (PAL) was also found to increase in plants pretreated with MSS2 challenge inoculated by FOL. Increase in total phenolics upto 1.7 fold was found in the plants treated with MSS2 challenge inoculated by FOL than untreated plants. Zymographic study for both defense enzymes showed induction of isoform PO2, PPO1 and PPO4 in the rhizobacterial treated plant challenged with pathogen than with untreated and pathogen control plants. Plant root colonizing ability of the rhizobacteria P. rettgeri MSS2 helps in the significant induction of enhanced plant defense response against phytopathogen FOL.

Inactivation kinetics of peroxidase and polyphenol oxidase in peach juice treated with gaseous ozone

AbstractThe effectiveness of gaseous ozone for inactivating peroxidase (POD) and polyphenoloxidase (PPO) in peach juice was investigated. The suitability of first‐order and Weibull models to describe inactivation kinetics was also analysed. Peach juice was exposed to ozone (0.11 and 0.20 mg O3 min−1 mL−1) in a bubble column up to 12 min at 20 ± 1 °C. Enzyme activities were reduced due to treatments. The magnitude of the inactivation increased with ozone level and exposure time. Reductions in activity after 12 min of treatment ranged between 99.5% and 99.8% for POD and between 93.9% and 97.3% for PPO, depending on ozone concentration. Inactivation curves were successfully fitted with the first‐order and Weibull models; although, based on the root‐mean‐square error, the corrected Akaike and the Bayesian Schwarz criterion, the Weibull model showed stronger capability in all cases.

UV-C enhances resistance against gray mold decay caused by Botrytis cinerea in strawberry fruit

The effect of ultraviolet C (UV-C) treatment on controlling gray mold caused by Botrytis cinerea in strawberry fruit and the possible mechanisms were investigated. The results showed that UV-C treatment significantly reduced lesion diameter and enhanced activities of chitinase (CHI), β-1, 3-glucanase, phenylalanine ammonia-lyase (PAL), peroxidase (POD) and polyphenoloxidase (PPO) in strawberry fruit. Total phenolic content were also increased by UV-C treatment. The activities of antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) were also higher in UV-C treated strawberry fruit than those in control. Expression of three defense related genes such as CCR-1 allele, CAT, CHI2, PPO and PLA6 was greatly induced in UV-C treated strawberry fruit. These results suggested that UV-C treatment directly activated disease resistance against gray mold caused by B. cinerea in strawberry fruit.

Biochemical markers to predict internal browning disorders in 'Rocha' pear during storage under high CO2.

The aim of this study was to identify biochemical markers to predict internal browning disorders (IBD) in 'Rocha' pear. Fruits from five orchards were stored for 45 days under cold air followed by 100 days in browning-inducing controlled atmosphere (CA) conditions (1 kPa O2 + 10 kPa CO2 ). Relationships between concentrations of ethanol (EtOH), acetaldehyde (AcDH) and ascorbic acid (AA), activities of peroxidase (POX) and polyphenoloxidase (PPO) and IBD incidence were established. The partial least square (PLS) model using the most promising markers, EtOH and AcDH, explained 89% of the variance in IBD incidence, whereas the univariate models based on the same markers explained between 89 and 94%. In contrast, the models based on AA levels and AA depletion rate only explained 57 and 82% of the variance in IBD incidence respectively. Model validation confirmed the robustness of EtOH for the prediction (R2 = 0.91, RMSE = 11.1) and allowed proposing a threshold level of 30 µL EtOH L-1 above which IBD may occur. Using this threshold value, the storage time limit associated with the occurrence of the first IBD symptoms was predicted with an acceptable RMSE of 9 days. This work clearly identifies biochemical IBD markers for 'Rocha' pear and shows that dynamic changes in ethanol concentration during the beginning of storage may be used to predict IBD development. Therefore the results presented herein represent a major step forward in the prediction of IBD in 'Rocha' pear. © 2017 Society of Chemical Industry.