Low Polyphenol Oxidase Activity Research Articles

Inhibitory potential of 7-hydroxycoumarin-3-carboxylic acid against tyrosinase and its effect on the preservation of fresh-sliced apples

Excessive tyrosinase expression leads to pigmented diseases in humans and browning in plants, necessitating effective tyrosinase inhibitors. This study investigated the inhibitory effect and mechanism of 7-hydroxycoumarin-3-carboxylic acid (7-HC-3-CA) on tyrosinase. Using UV–visible absorption spectroscopy, we found that 7-HC-3-CA effectively inhibited tyrosinase activity, with an IC50 value of 364 ± 1.3 μM. Enzyme kinetics, fluorescence methods and molecular simulation techniques revealed that 7-HC-3-CA acted as a reversible and competitive inhibitor, forming a stable complex with tyrosinase through hydrophobic interactions and hydrogen bonding. This altered the microenvironment of Tyr and Trp residues, causing the structural stretching and conformational changes that diminish catalytic activity.Preservation experiments demonstrated that 0.5 mM 7-HC-3-CA significantly reduced mass loss and decreased browning of fresh-sliced apples. It also lowered polyphenol oxidase activity from 0.22 to 0.18 and delayed phenolic oxidation, enhancing total phenolic content from 0.34 to 0.54, thereby controlling browning and extending storage life. Cell assays indicated that 0.5 mM 7-HC-3-CA had no significant impact on cell proliferation, with viability over 80 %. Acute toxicity tests proved that 0.5 mM of 7-HC-3-CA is completely non-lethal to KM mice. In conclusion, this study confirmed 7-HC-3-CA was a viable and safe antibrowning agent and revealed its potential application in the field of food preservation.

Assessment of microwave drying for rapid and convenient analysis of medicinal plants for quality assurance.

The safety and quality of many medicinally important herbs are compromised since farmers and small organizations are involved in the cultivation, aggregation, and primary processing of these herbs. Such organizations often lack adequate quality control facilities. To improve the safety and quality of herbal products, simple, rapid, and affordable quality control systems are required. The aim of this study was to assess the suitability of microwave oven-drying for moisture content (MC) determination and sample preparation of herbs in small organizations. Microwave oven-drying (720 W) and convective oven-drying at 105°C for MC determination were compared. The effects of three different drying methods (microwave oven-drying, low-temperature convective drying, and freeze-drying) on in vitro antioxidant and polyphenol oxidase (PPO) activity were determined, similarity analysis was conducted using HPLC signature spectra, and validation was performed with LC-MS focusing on one herb. Microwave oven-drying at 720 W significantly reduced the drying time (from hours to minutes), whereas the spatial variationof temperature in convective ovens set at 105°C can cause about 10% underestimation of MC. Microwave oven-dryingshowed similar macro-properties like freeze-drying and higher extractability (10%-20%) and in vitro antioxidant capacity (33%-66%) and lower PPO activity compared to low-temperature convective drying. HPLC signature spectra revealed strongsimilarity ofsoluble components between freeze-dried and microwave oven-dried herbs. LC-MS analysis demonstrated more common compounds between freeze-driedand microwave oven-driedCentella asiatica extracts, whereas convective tray-dried samples had fewer compounds common with samples obtained by freeze-drying or microwave oven-drying. Microwave oven-drying is rapid (tens of min) and shows small batch-to-batch variation compared to oven-drying at 105°C. The in vitro antioxidant assays and signature spectra can be used for assessing the source and purity or quality of a specific herb variety.

Pre-storage calcium chloride and aloe vera gel coatings mitigate internal browning and senescence scald in ‘Conference’ pears

Physiological disorders pose significant challenges to the quality and shelf life of ‘conference’ pears. This study investigates the efficacy of calcium chloride (CaCl2) and aloe vera (AV) gel treatments in reducing internal browning and senescence scald in ‘Conference’ pears. Four groups were evaluated: a control, individual 2 % CaCl2, 15 % AV gel treatments, and a combined CaCl2 and AV gel treatment. Pears having following maturity indices (TSS 12 %, ho 90, and Firmness 67 N) were then stored at 2 ± 1 °C, 85±5 % RH for 180 d The fruits were removed from cold storage to room temperature and kept at 20±3 °C and 65±5 % RH followed by physicochemical and sensory analyses. The combined treatment proved most effective in preserving quality and reducing internal browning and senescence scald. Treated pears displayed reduced respiration rates, ethylene production, internal browning, senescence scald, and weight loss. Moreover, the combined treatment resulted in higher TA and lower TSS compared to the control after 180 d of storage. The reduction in internal browning and senescence scald can be attributed to enzyme activity modulation. The combined treatment increased catalase (CAT) and superoxide dismutase (SOD) activity, reducing oxidative stress. This, in turn, minimized oxidative reactions leading to internal browning. Furthermore, the treatment inhibited polyphenol oxidase (PPO) and peroxidase (POD) activity, enzymes responsible for browning reactions. Lower PPO and POD activity contributed to reduced internal browning and senescence scald. The combined actions of enhanced antioxidant enzymes and decreased browning-related enzymes synergistically reduced internal browning. In conclusion, the combined CaCl2 and AV gel treatment effectively mitigated internal browning and senescence scald in pears and also received the highest score in sensory analysis. Enhanced antioxidant enzyme activity (CAT and SOD) and reduced PPO and POD activity collectively contributed to this reduction. This eco-friendly approach presents a sustainable strategy for extending shelf life and enhancing pear quality, providing an alternative to traditional chemical interventions for managing physiological disorders.

Comparative physiochemical and transcriptomic analysis reveals the influences of cross-pollination on ovary and fruit development in pummelo (Citrus maxima)

‘Shuijingmiyou’ pummelo (SJ), one of the most popular fruits in Yunnan province of China, is of relatively low fruit shape (FS) quality. In this study, we compared the FS promoting effects of cross pollinations using pollens from seven pummelo varieties, and found that ‘Guanximiyou’ pummelo (GX) cross-pollination showed the best FS promoting effects on SJ fruits by shortening its fruit neck. To explore the underlying mechanism, physiochemical and transcriptomic differences between self- and cross-pollinated SJ ovaries (SJO and GXO) were investigated. Higher salicylic acid, gibberellin and indole acetic acid contents and superoxide dismutase, peroxidase and catalase activities, and lower polyphenol oxidase activity were determined in GXO compared with SJO. Enrichment analysis of the identified 578 differentially expressed genes (123 up-regulated and 455 down-regulated) in GXO showed that genes involved in solute transport, RNA biosynthesis, phytohormone action and cell wall organization were significantly enriched. The results obtained in this study will be helpful in understanding the influences of cross-pollination on pummelo ovary and fruit development, and can provide the basis for clarifying the underlying mechanism of cross-pollination improved fruit quality.

Elucidating the effects on polyphenol oxidase activity and allelic variation of polyphenol oxidase genes on dough and whole wheat-derived product color parameters

ABSTRACT Polyphenol oxidase (PPO) activity is a primary cause of the development of unattractive dark brown discoloration of wheat-based end products. The present study aims to evaluate a set of 41 diverse wheat genotypes grown at three different locations in India for grain phenol color reaction, PPO activity and molecular marker-based characterization of alleles of PPO genes. Relationships among these parameters were analyzed along with the effects of grain PPO activity on dough and chapati color at different time intervals. The mean PPO activity ranged from 7.42 to 27.57 min−1 g−1 10−3 among the genotypes and it showed a significant negative correlation with color brightness (L*) of dough rested for 0 min (r = -0.406), 15 min (r = -0.406), 2 h (r = -0.502) and 4 h (r = -0.551) and whole wheat flour-derived chapati rested for 2 h (r = -0.267) and 4 h (r = -0.424). The overall quality color score was negatively correlated with PPO activity (r = -0.863) and showed a positive correlation with both dough and chapati visual color measured at different time intervals. PPO activity in the genotypes carrying different alleles was found to be Ppo-A1a>Ppo-A1b; Ppo-B2d>Ppo-B2a; and Ppo-D1b>Ppo-D1a. The allelic constitution Ppo-A1bPpo-B2aPpo-D1a and Ppo-A1bPpo-B2dPpo-D1 was found to produce the lowest PPO activity, and thus these alleles are recommended to be used in marker assisted breeding for low PPO activity genotypes to minimize the discoloration of wheat-based end-products.

Functional analysis of polyphenol oxidase 1 gene in common wheat.

Polyphenol oxidase (PPO) activity is a major cause of the undesirable brown color of wheat-based products. Ppo1, a major gene for PPO activity, was cloned based on sequence homology in previous studies; however, its function and regulation mechanism remain unclear. In this study, the function and genetic regulation of Ppo1 were analyzed using RNA interference (RNAi) and Targeting Induced Local Lesions IN Genomes (TILLING) technology, and superior mutants were identified. Compared with the control, the level of Ppo1 transcript in RNAi transgenic lines was drastically decreased by 15.5%-60.9% during grain development, and PPO activity was significantly reduced by 12.9%-20.4%, confirming the role of Ppo1 in PPO activity. Thirty-two Ppo1 mutants were identified in the ethyl methanesulfonate (EMS)-mutagenized population, including eight missense mutations, 16 synonymous mutations, and eight intron mutations. The expression of Ppo1 was reduced significantly by 6.7%-37.1% and 10.1%-54.4% in mutants M092141 (G311S) and M091098 (G299R), respectively, in which PPO activity was decreased by 29.7% and 28.8%, respectively, indicating that mutation sites of two mutants have important effects on PPO1 function. Sequence and structure analysis revealed that the two sites were highly conserved among 74 plant species, where the frequency of glycine was 94.6% and 100%, respectively, and adjacent to the entrance of the hydrophobic pocket of the active site. The M092141 and M091098 mutants can be used as important germplasms to develop wheat cultivars with low grain PPO activity. This study provided important insights into the molecular mechanism of Ppo1 and the genetic improvement of wheat PPO activity.

Vegetative Growth and Productivity of Potted Crocus sativus in Different Growing Media

Saffron (Crocus sativus) is the most expensive spice in the world and a valuable medicinal plant. In this study, the flowering, vegetative growth performance, and daughter corm formation of potted saffron were investigated in six growing media: loamy soil, silty soil, sandy soil, peatmoss, peatmoss + sandy soil, and peatmoss + foam. The highest values of the stigma fresh weight, the root weight, and the number and diameter of daughter corms were observed in plants grown in soil with a light texture, i.e., sandy soil or peatmoss + foam, although smaller daughter corms were produced by sandy soil-grown plants. Compared with loamy soil (heavy soil), the peatmoss + foam growing medium increased the leaf pigment levels and the number of leaves and daughter corms, and it produced the highest number of daughter corms with diameters of ≥2 cm. Compared with plants in other media, saffron plants grown in loamy soil had higher catalase and peroxidase activities but lower polyphenol oxidase activity. Overall, saffron could be cultivated and produced in growing media with various pH values (4.00–9.25), although a mixture of peatmoss and foam was the optimal growing medium for potted saffron production. These findings are beneficial for selecting the optimal growing media/soil for saffron cultivation in farmlands.

Effect of pre-treatment and freezing on the polyphenol oxidase activity and color stability of sliced peaches.

A study was conducted to determine the polyphenol oxidase (PPO) activity and changes in surface color and hydroxymethylfurfural (HMF) content in fresh and pre-frozen peach slices stored at different temperatures. In this study, fresh (F) and pre-frozen (P) peaches were subjected to one of four treatments: (i) no treatment (N); (ii) blanching in boiling (96 °C ± 4°C) water (B); (iii) dipping in 2% l-ascorbic acid and 2% citric acid (AC); or (iv) blanching placed in boiling water, cooling and dipping in 2% ascorbic acid and 2% citric acid (BAC). Peaches from each treatment group were held at -7, -9, or - 12 °C for 21 days. After 21 days of storage, PPO activity and browning was greater in peaches stored at -7°C than the PPO activity and browning of peaches stored at -9°C and - 12 °C. Overall, lightness (L*), yellowness (b*), chroma (c*) and hue (h*) decreased while redness (a*) increased during storage. The BAC peaches had less discoloration and lower PPO activity than peach slices exposed to other treatments. Non-enzymatic browning (HMF indicator) was more pronounced for blanched peaches during storage than unblanched peaches. Pretreatment of blanched peaches with ascorbic and citric acid reduced browning during 21 days at frozen storage for peaches held at -9°C or - 12 °C. Storage at -12 °C significantly reduced browning and HMF formation in both blanched and unblanched peach slices in comparison with -7°C storage. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Ultrasonic treatment decreases Lyophyllum decastes fruiting body browning and affects energy metabolism

Lyophyllum decastes is a common mushroom that is prone to browning during prolonged storage. In this study, the effects of ultrasonic treatment on metabolic gene expression, enzyme activity, and metabolic compounds related to L. decastes browning were investigated. Treatment of the fruiting body at 35 kHz and 300 W for 10 min reduced the browning index of L. decastes by 21.0 % and increased the L* value by 11.1 %. Ultrasonic treatment of the fruiting body resulted in higher levels of total phenols, flavonoids, and 9 kinds of amino acid with catalase (CAT) and peroxidase (POD) activities maintained at high levels. Higher cytochrome c oxidase (CCO), succinate dehydrogenase (SDH), phosphofructokinase (PFK), and pyruvate kinase (PK) activities may be ascribed to increased antioxidant capacity. Moreover, ultrasonication retained higher adenosine triphosphate (ATP) concentrations with an increased energy charge, while there were lower levels of adenosine diphosphate (ADP) and reduced and oxidized nicotinamide adenine dinucleotide (NADH and NAD+), respectively. Meanwhile, lower lignin contents were observed, along with retarded polyphenol oxidase (PPO) and lipoxygenase (LOX) activities. Lower PPO activity reduced the fruiting body enzymatic browning rate through decreased expression of LdPpo1, LdPpo2, and LdPpo3 during storage at 4 °C for 16 days. This activity may be used to determine the effectiveness of ultrasonication.

Effect of pulsed light treatment on the physicochemical properties of wheat flour and quality of fresh wet noodles

AbstractBackground and ObjectivesPulsed light (PL) was first applied to the production of low bacterial wheat flour—treating wheat kernels with PL. The effect of PL on the physicochemical properties of wheat flour and the quality of fresh wet noodles (FWN) were investigated.FindingsAfter treatment, the total plate count (TPC), yeast and mold count (YMC) in wheat flour decreased significantly. Wet gluten content and the stability time reached their maximums when the pulsed flash frequency was 10 c. Starch viscosity increased slightly, mainly due to an increase in damaged starch content. Secondary structures altered remarkably, which were consistent with changes in gluten protein microstructures. Moreover, the textural properties of FWN were improved greatly. Browning of FWN was significantly inhibited because of low polyphenol oxidase (PPO) activity in wheat flour.ConclusionPL was effective in decreasing the initial microorganisms in wheat flour as well as improving the quality of dough and FWN, and the optimum treatment was pulsed energy of 500 J, pulsed flash distance of 9 cm, and pulsed frequency of 10 c.Significance and NoveltyThese results showed that PL treatment could decrease TPC and YMC in wheat flour significantly, improve farinograph and pasting properties, change gluten protein microstructures and secondary structures, as well as improve textural properties of FWN and inhibit its darkening greatly, which provided a new method for low bacterial wheat flour production and promoted PL's industrialization.

Evaluation of ‘Lorca’ Cultivar Aptitude for Minimally Processed Artichoke

Previous research works have reported that ‘Lorca’ artichoke cultivar presents a lower total phenolic content than other cultivars rich in phenolic compounds, which could show a lower susceptibility to enzymatic browning and increase its aptitude for fresh-cut processing. The aim of this study was to analyze the total phenolic content as well as browning evaluation by image analysis and polyphenol oxidase (PPO) enzyme activity in ‘Lorca’ cultivar in order to characterize the key factors which influence its phenolic levels for minimally processed artichokes. Thus, artichokes were harvested and classified on three head orders (main, secondary, and tertiary), as well as three development stages (initial, intermediate, and advanced). Variance components analysis was carried out for total phenolic content considering three factors: plant, flower head order, and internal development stage. For the first time, the internal development stage has been related to total phenolic content, and results showed that artichoke head order and internal development stage were responsible for a variability of 22.17% and 15.55%, respectively. Main artichoke heads and those at the advanced development stage presented the lowest phenolic concentration as well as the lowest PPO activity; therefore, they exhibit the lowest browning process, which could increase their use in ready-to-eat products at market.

Effects of polysaccharide-based coatings on postharvest storage life of grape: measuring the changes in nutritional, antioxidant and phenolic compounds

In this study, the effect of postharvest coating of chitosan (CH) 1.0%, gum ghatti (GG) 1.0% and combine of each other, on nutritional properties, phenolic compounds and antioxidant capacity of ‘Rishbaba’ grape (Vitis vinifera L.) was evaluated during 60 days of cold storage. Coating with 1.0% CH solely or in combined with 1.0% GG caused a considerable retain in grape berries phenolic acids compared to uncounted samples after the 60th day. Moreover, flavanols and flavan-3-ols content were found to be highest in fruits treated with CH and GG complex. At the end of storage, the highest concentrations of delphinidin, cyanidin, pelargonidin and malvidin were found in grapes coated with CH in combined with GG. The highest antioxidant capacity and the lowest polyphenol oxidase activity were related to samples treated with CH and GG complex. Also, the combination effects of CH and GG at 1.0% were the most efficient for soluble sugars and polyamines accumulation. The CH + GG complex had the best result on prohibiting grape fungal decay. The results showed a research increase of this complex that these are a strong potential strategy to produce coatings for improving the postharvest quality of fruits and could be considered as a good solution to preserve many components of them.

Effects of non‐thermal plasma treating wheat kernel on the physicochemical properties of wheat flour and the quality of fresh wet noodles

AbstractThe effects of non‐thermal plasma (NTP) on the physicochemical properties of wheat flour and the quality of fresh wet noodles (FWN) were investigated. The results showed that NTP effectively decreased the total plate count (TPC), yeast and mould count (YMC) and Bacillus spp. in wheat flour. Wet gluten contents and the stability time reached the maximum when treated for 20 s. The viscosity of starch increased significantly after treatment due to the increased of damaged starch. The contents of secondary structure were altered to some extent, which was because that the ordered network structure of gluten protein broken. Furthermore, compared with the control, texture properties of FWN were enhanced significantly at 20 s, and the darkening rate of FWN was greatly inhibited due to the low polyphenol oxidase (PPO) activity. Consequently, the most suitable treatment was 500 W for 20 s, providing a basis for the application of NTP in flour products.

Combinational effect of chemical treatments on quality of litchi (Litchi chinensis) during storage

Attractive red-coloured pericarp is one of the most important factors in the consumer decision to purchase litchi(Litchi chinensis Sonn.). Red colour of the pericarp turns brown within 2-3 days after harvest which reduces themarketability and commercial value of the fruit drastically and finally incurring huge financial losses to growers.This study was carried out to evaluate the possibility of using combinational application of sodium hypochlorite withsodium chlorite and carnauba wax on the quality of harvested litchi during storage (2016–17). Postharvest treatmentsincluded sequential dipping in sodium hypochlorite (0.2%) (T1), sodium hypochlorite (0.2%) + sodium chlorite (0.05%) (T2), sodium hypochlorite (0.2%) + carnauba wax (10%) (T3) and untreated (control) (T4). Treated fruit werethen packed inplastic punnets and stored at 2°C and 90-95% relative humidity (RH). All the treatments significantlyreduced pericarp browning over control. The most remarkable effect was obtained in fruits treated with sodiumhypochlorite (0.2%) in combination with sodium chlorite (0.05%) as evidenced by delayed anthocyanin degradation,lower polyphenol oxidase activity, fruit decay and weight loss. This treatment also maintained better fruit quality asindicated by higher total soluble solids and phenolic content in fruits, thus can be used as a cost-effective method toreduce pericarp browning and prolong marketable life of litchi up to 25 days.

Association of Polyphenol Oxidase Activities with Molecular Markers and Yellow Rust Resistance in Diverse Bread Wheat Genotypes

Polyphenol Oxidase (PPO) catalyses the undesirable browning of wheat products which is of significant concern in consumer acceptance perspectives. Another important yield-limiting cause for wheat crops is wheat rust (e.g., yellow rust), a source of great economic loss worldwide. The purpose of the current research was to screen conventional and synthetic bread wheat genotypes for their PPO activity and yellow rust resistance. Different genotypes differed significantly in total PPO activity and in their activities against different substrates (L-DOPA and Catechol). The synthetically derived bread wheat genotypes 1-279, showed the lowest (39.2 units/min/g) cumulative PPO activity. Ten genotypes each with the highest and lowest PPO activities were selected for testing their association with seven reported molecular markers. Intriguingly the PPO markers reported in literature could not clearly differentiate between contrasting cultivars. Association with yellow rust resistance was also investigated. Interestingly, the rust-resistant genotypes, including 1-263, Ch-43, 1-57 and Emat (all synthetic-derived), exhibited low PPO activity. The current study underpins that there is a need to search for more reliable PPO markers and to further validate association of low PPO activity with yellow rust.

Blanching Pre-Treatment Promotes High Yields, Bioactive Compounds, Antioxidants, Enzyme Inactivation and Antibacterial Activity of 'Wonderful' Pomegranate Peel Extracts at Three Different Harvest Maturities.

‘Wonderful’ pomegranate (Punica granatum L.) peel contains a wide range of phytochemicals including vitamins, dietary fibre, phenolic compounds, and antioxidant properties. Yet, it is often used as animal feed or discarded in landfills, which is not the best eco-friendly way to utilize this phenolic-rich bioresource. Finding novel ways of utilizing pomegranate peel waste could prove a more profitable and eco-friendlier alternative that is far more beneficial to the economy. Adding a blanching pre-treatment step at optimal conditions prior to processing of pomegranate peel aids in the inactivation of quality changing enzymes such as polyphenol oxidase (PPO) and peroxidase (POD), which are accountable for the degradation reactions that cause breakdown of nutrients and phytochemicals. This study aimed to determine the effect of blanching at 80 °C for 3 min on the yield, polyphenol content, antioxidant properties, enzyme inactivation, and antibacterial activity of ‘Wonderful’ pomegranate peel ethanolic extracts from three different harvest maturities (unripe, ripe, and over ripe), including a comprehensive characterization and quantification using liquid chromatography-mass spectrometry (LC-MS). The blanched unripe peel extracts exhibited the highest total phenolic content, total tannin content, 2,2-diphenyl-1-picryl hydrazyl (DPPH) antioxidant activity, 2,2-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid (ABTS) radical scavenging activity and ferric ion reducing antioxidant power (FRAP) at 14.0 mg gallic acid equivalent (GAE)/g dry mass (DM), 1.0 mg GAE/g DM, 359.1 µmol Trolox/g DM, 912.2 µmol Trolox/g DM and 802.5 µmol Trolox/g DM, respectively. There was significant (p < 0.05) decrease in PPO and POD activity of all blanched pomegranate peel extracts. The blanched unripe peel extracts had the lowest PPO activity at 0.2 U/g fresh weight (FW), with a 70% PPO inactivation compared to ripe and over ripe harvest, whereas the highest POD inactivation was recorded at 67% in over ripe peel extracts. All blanched peel extracts, irrespective of harvest maturity, had minimum inhibitory concentration (MIC) values at 160 µg/mL against all four bacteria strains tested, which included two Gram-positive bacterial strains (Bacillus subtilis ATCC 6051 and Staphylococcus aureus ATCC 12600) and two Gram-negative bacteria (Escherichia coli 11775 and Klebsiella pneumonia ATCC 13883). A total of 25 metabolites including phenolic acids (4), organic acids (1), flavonoids (4), ellagitannins (13), and other polyphenols (3) in all three pomegranate peel samples were tentatively identified after LC-MS profiling. The blanched unripe peel extracts showed significantly higher punicalin α and β, β punicalagin, catechin, epicatechin content at 414 mg/g, and 678 mg/g, 151 mg/g, 229 mg/g, respectively, compared to peel extracts from other harvest maturities. This study provides supportive information for the commercial utilization of pomegranate fruit peel as source of value-added ingredients for the development of novel food, cosmetics, and pharmacological products.

Relationship between the allelic variations at the&amp;lt;italic&amp;gt; Ppo-A1 &amp;lt;/italic&amp;gt;and &amp;lt;italic&amp;gt;Ppo-D1&amp;lt;/italic&amp;gt; loci and pre-harvest sprouting resistance in wheat

<p indent=0mm><italic>Ppo-A1</italic> and <italic>Ppo-D1</italic> are the major genes that control the activity of polyphenol oxidase (PPO) in wheat. It has been reported that the activity of polyphenol oxidase affects pre-harvest sprouting (PHS) resistance, but the effect of different alleles/allelic combinations at the <italic>Ppo-A1</italic> and <italic>Ppo-D1 </italic>loci on PHS resistance remains unclear. The current study was carried out to elucidate the effects based on the germination index obtained from 248 Chinese wheat cultivars in a three-year trial in combination with genotypic data at the <italic>Ppo-A1</italic> and <italic>Ppo-D1 </italic>loci. Analysis of variation for the<italic> Ppo-A1 </italic>and <italic>Ppo-D1</italic> loci showed that year,<italic> Ppo-A1</italic> locus and<italic> Ppo-A1</italic> × <italic>Ppo-D1 </italic>interaction had significant effects on germination index. At locus <italic>Ppo-A1</italic>, germination index of cultivars carrying the allele <italic>Ppo-A1b</italic> of low PPO activity was 5.22% lower than that carrying the allele<italic> Ppo-A1a</italic> of high PPO activity on average. In contrast, the cultivars carrying the allele <italic>Ppo-D1a</italic> of low PPO activity had higher germination index than that carrying the allele<italic> Ppo-D1b</italic> of high PPO activity at locus<italic> Ppo-D1</italic>, but no significant differences between two alleles. Among the four allelic combinations, the cultivars with the <italic>Ppo-A1bPpo-D1b</italic> had the lowest germination index. The relationship between the alleles at locus <italic>Ppo-A1</italic> and PHS resistance had been verified in the Lunxuan 13 × Jimai 20 F₂ and F_2:3 segregation populations. There were significantly positive correlations between PPO activity / relative expression level of <italic>Ppo-A1</italic> gene and germination index. This study suggests that functional markers of allele<italic> Ppo-A1b </italic>can be effectively applied in marker-assisted selection for PHS resistance.

Molecular marker assisted screening for kernel polyphenol oxidase activity in wheat Triticum aestivum L.

High level of kernel polyphenol oxidase (PPO) activity has been found to be the major factor behind time-dependent discolouration of wheat-based products, which ultimately leads to reduced consumers’ preference. Till date, 6 genes belonging in 2 paralogous sets present in wheat (Triticum aestivum L.) chromosome 2 homeologues (2A, 2B and 2D) have been reported to govern kernel PPO activity. Among these 6 genes, perfect molecular markers have been developed for 2 genes (PPOA1 and PPOD1) and the major role of PPOA1 gene in governing kernel PPO activity in wheat has been reported. In the present study we have used the molecular markers for the PPOA1 and PPOD1 genes to characterize wheat genotypes for their kernel PPO activity. We have successfully converted the dominant marker assay for the PPOD1 locus into a co-dominant assay using the already reported primers. Our molecular screening strategy could explain the kernel PPO activity of wheat genotypes in rapid, reliable and environment-independent manner. Furthermore, biochemical estimation of kernel PPO activity in wheat genotypes indicated the involvement of other genes in fine-tuning this important trait. Thus, the present study should facilitate the breeders in marker-assisted selection and breeding for developing wheat genotypes with low kernel PPO activity.

Postharvest methyl jasmonic acid and hot water can reduce the internal breakdown and quality loss of apricot fruit at shelf life

The aim of this study was to investigate the postharvest effect of methyl jasmonic acid (MJ) and hot water on internal break-down and quality loss of apricot fruit under shelf life conditions. Cultivar Flavor cot apricot fruit were used to treat with water as control treatment, with 0.2 mmol/L MJ and with hot water 35 oC for 5 min. Fruit were stored at room temperature and were examined every 2 days for internal break-down and quality loss. Results showed that treated fruits with MJ and hot water showed the lowest weight loss and the highest firmness during all assessment times. Control fruits showed losing of customer acceptance from the day 2 of shelf life and then decreased dramatically to approximately loss all the acceptance at day 8. The SSC showed sever reduction in untreated fruit after day 6 at shelf life. Total phenol content reduced and polyphenol oxidase (PPO) increased in all assessment times for all treatments. Meanwhile MJ showed the best values for phenol content and lowest PPO activity. The results supported the idea of using some elicitors like methyl jasmonic and hot water treatments to enhance shelf life of apricot fruit.

Pectin-based edible coating preserves antioxidative capacity of plum fruit during shelf life.

Exploiting safer methods for fruit preservation such as application of edible coatings can improve shelf life, valuable characteristics, and antioxidative capacity. The current study aimed to investigate the effect of a pectin-based edible coating on antioxidative capacity of plum fruit during shelf life (19 ± 2 ℃ and 65% relative humidity for eight days). To do this, three solutions (0.5, 1, and 1.5%) of pectin, plasticized by glycerol (0.3% w/v), were applied on plum fruit and compared to a control treated with only distilled water. Ascorbic acid, total phenolics, anthocyanin and flavonoid contents, total antioxidative capacity based on 1,1-diphenyl-2-picryl-hydrazyl hydrate method, peroxidase (as an antioxidant enzyme), and polyphenol oxidase (as an oxidant enzyme) activities were recorded during this period. The results demonstrated that pectin-based edible coating was significantly effective on maintaining ascorbic acid, anthocyanin and flavonoid contents, and antioxidative capacity in plum fruits (P ≤ 0.01). The activities of enzymes were significantly affected by the coatings; peroxidase activity increased and polyphenol oxidase activity decreased (P ≤ 0.01). All pectin concentrations significantly caused higher ascorbic acid and anthocyanin contents, antioxidative capacity, and peroxidase activity but a lower polyphenol oxidase activity than the control; however, just 1 and 1.5% concentrations were effective in terms of total phenolic compounds and flavonoid content, respectively, and the other concentrations acted the same as the control. In general, the coating constituted from 1.5% pectin showed the best results for most measured parameters. Considering the influences of pectin-based edible coating on antioxidative characteristics of plum fruits, its application can be potentially regarded as a favorable method to enhance nutritional value of fruits.