SA-treated Fruit Research Articles

Plant biostimulants as natural alternatives to synthetic auxins in strawberry production: physiological and metabolic insights.

The demand for high-quality strawberries continues to grow, emphasizing the need for innovative agricultural practices to enhance both yield and fruit quality. In this context, the utilization of natural products, such as biostimulants, has emerged as a promising avenue for improving strawberry production while aligning with sustainable and eco-friendly agricultural approaches. This study explores the influence of a bacterial filtrate (BF), a vegetal-derived protein hydrolysate (PH), and a standard synthetic auxin (SA) on strawberry, investigating their effects on yield, fruit quality, mineral composition and metabolomics of leaves and fruits. Agronomic trial revealed that SA and BF significantly enhanced early fruit yield due to their positive influence on flowering and fruit set, while PH treatment favored a gradual and prolonged fruit set, associated with an increased shoot biomass and sustained production. Fruit quality analysis showed that PH-treated fruits exhibited an increase of firmness and soluble solids content, whereas SA-treated fruits displayed lower firmness and soluble solids content. The ionomic analysis of leaves and fruits indicated that all treatments provided sufficient nutrients, with heavy metals within regulatory limits. Metabolomics indicated that PH stimulated primary metabolites, while SA and BF directly affected flavonoid and anthocyanin biosynthesis, and PH increased fruit quality through enhanced production of beneficial metabolites. This research offers valuable insights for optimizing strawberry production and fruit quality by harnessing the potential of natural biostimulants as viable alternative to synthetic compounds.

Salicylic acid treatment delayed the browning development in the pericarp of fresh longan by regulating the metabolisms of ROS and membrane lipid

Longans is popular among consumers because of its rich nutritional value, but it is prone to pericarp browning as it is harvested in the high-temperature season. This work was to investigate the effects of salicylic acid (SA) on the metabolisms of reactive oxygen species (ROS) and membrane lipid and their relationship with pericarp browning of postharvest longans. ‘Fuyan’ longans were soaked in the solution of 0.3 g L-1 SA for 5 min, then stockpiled at 28 °C. The results showed that, the pericarp browning index in SA-treated fruit was 42% lower than that in the control fruit at day 5 of storage. Meanwhile, SA treatment reduced the damage severity of cell membrane structure, and maintained a low level of cell membrane permeability, which was 25% lower than that in the control fruit at day 5 of storage. Additionally, compared to the control fruit, SA-treated longans displayed higher levels of pericarp L*, flavonoid, chlorophyll, carotenoid, total phenolics, and anthocyanin, higher activities of pericarp superoxide dismutase, catalase, and ascorbate peroxidase, higher values of pericarp reducing power and 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging ability, and higher amounts of pericarp ascorbic acid and glutathione, but lower levels of pericarp ROS and malondialdehyde. Moreover, SA-treated samples exhibited lower activities of pericarp phospholipase, lipase, and lipoxygenase, lower levels of pericarp phosphatidic acid and saturated fatty acids (SFA), but higher values of pericarp phosphatidylcholine, phosphatidylinositol, and unsaturated fatty acids (USFA), higher index of USFA, and higher ratio of USFA to SFA. These findings corroborated that SA delayed-browning occurrence in the pericarp of fresh longans was because SA enhanced the capacity to remove ROS, and reduced ROS accumulation and the membrane lipid degradation, thus maintaining the cellular membrane structure, reducing the degradation of pigments, and allowing the fresh longans to maintain a better appearance. Consequently, SA could be an effective means for suppressing pericarp browning and improving the commercial value of fresh longans.

Exogenous salicylic acid regulates organic acids metabolism in postharvest blueberry fruit.

Fruit acidity is an essential factor affecting blueberry organoleptic quality. The organic acid content in blueberry fruit mainly contributes to fruit acidity. This study aims to evaluate the effect of exogenous salicylic acid (SA), the principal metabolite of aspirin, on the organoleptic quality and organic acid metabolism in rabbiteye blueberry (Vaccinium virgatum Ait, 'Powderblue') during cold storage (4 °C). Results showed that SA-treated fruit reduced fruit decay and weight loss delayed fruit softening, and decline of total soluble solids (TSS). TA and total organic acid amounts stayed the same during the late storage period in SA-treated fruit. Four kinds of organic acid components, malic acid, quinic acid, citric acid, and succinic acid, were at higher levels in fruit treated by SA as compared to control. SA enhanced the activities of PEPC, NAD-MDH, and CS to promote the synthesis of malic acid and citric acid. Meanwhile, the activities of NADP-ME, ACL, and ACO, which participated in the degradation of malic acid and citric acid, were inhibited by SA. qPCR results also showed that the expression of VcPEPC, VcNAD-MDH, and VcCS genes were upregulated. In contrast, SA downregulated the expression of VcNADP-ME, VcACL, and VcACO genes. In conclusion, SA could regulate the key genes and enzymes that participated in organic acids metabolism to maintain the freshness of blueberry during cold storage, therefore minimizing the economic loss.

Salicylic acid treatment inhibits ethylene synthesis and starch-sugar conversion to maintain apple fruit quality during shelf life

Starch and sugars are widely acknowledged as taste determinants, energy substances, and signal molecules in fruits. Salicylic acid (SA) regulates many physiological and biochemical processes during fruit ripening. In this work, we investigated the effects of SA treatment on physiological parameters and SA synthesis, ethylene production, and starch-sugar metabolism of apples during shelf life. Results showed that SA maintained fruit firmness, reduced weight loss, and inhibited starch to sugar conversion during shelf life. The endogenous SA level was increased in SA-treated fruits, mediated by MdPAL, MdICS2, and MdNPR1, thus decreasing MdACS1 and MdACO1 expressions and inhibiting ethylene biosynthesis. Furthermore, the expression of starch and sugar-related genes, MdAMY, MdBam5, MdBam8, MdSPS, MdSUSY, MdNINV, and MdAINV, were inhibited by SA treatment during shelf life. It was inferred that exogenous SA could inhibit ethylene synthesis and starch-sugar conversion, maintain the quality, and prolong the shelf life of apples

Blue light combined with salicylic acid treatment maintained the postharvest quality of strawberry fruit during refrigerated storage.

Strawberryis a high economic and nutritional valuefruit,but marketing is limited by a short postharvest life. The objective of this work is to assess the influence of blue light (BL) and salicylic acid (SA, 2mM) on strawberry postharvest quality during cold storage. The results showed that the combination of BL and SA noticeably delayed weight loss, prevented decay, improved fruit skin brightness, and increased soluble protein. Strawberries treated with BL+SA had lower total soluble solids and titratable acidity contents among treatments but had no significant change during the entire storage. Additionally, contents of total flavonoids, phenolics, anthocyanins and proanthocyanidins, activities of superoxide dismutase (SOD) and ascorbate peroxidase (APX) and total antioxidant capacities in BL+SA-treated fruit were kept at stable levels throughout the entire storage. Collectively, these findings suggest that BL+SA treatment exhibits a high potential in maintaining postharvest fruit quality of strawberry fruit.

Enhancement of Anti-Inflammatory and Antioxidant Activities of Mango Fruit by Pre- and Postharvest Application of Salicylic Acid

Mango fruits have a high nutritional value and are beneficial to health. However, losses frequently occur after harvest, because they are perishable. Salicylic acid (SA) can be used to preserve fruit quality and maintain their nutritional contents. Therefore, this study was conducted to investigate the effects of applications of 2 mM SA on the physicochemical properties, bioactive compounds, and antioxidant and anti-inflammatory activities of mango fruit. For this purpose, mango fruits received preharvest (Pre SA) or postharvest applications of SA (Post SA), or their combination (Pre + Post SA); the fruits were stored at 13 °C for 20 days. Weight loss, decay, and 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) radical scavenging activity were maintained in SA-treated fruit. The Pre + Post SA treatment was superior in delaying fruit ripening, and maintaining lower soluble solids contents and higher total acidity. In addition, total phenolic compounds, ferric reducing antioxidant power, and free radical scavenging activity of anti-inflammatory substances (such as nitric oxide), as well as hyaluronidase inhibition, were higher in the Pre + Post SA treatment throughout storage. Therefore, both pre- and postharvest SA treatments are recommended for preserving the quality of mango fruit, such as Nam Dok Mai Si Thong, and for maintaining their nutritional properties for human health.

Temporal Patterns and Inter-Correlations among Physical and Antioxidant Attributes and Enzyme Activities of Apricot Fruit Inoculated with Monilinia laxa under Salicylic Acid and Methyl Jasmonate Treatments under Shelf-Life Conditions.

Monilinia laxa causes serious postharvest damage on apricot fruits under shelf-life storage conditions. Plant elicitors of methyl jasmonate (MeJA) and salicylic acid (SA) can reduce this damage, and their research can explain the background of the plant defense physiological processes in M. laxa-infected fruits. The aims of this study were: (i) to evaluate the effect of various concentrations of MeJA and SA on brown rot incidence (BRI) and lesion diameter (LD) of apricot fruits; (ii) to measure the temporal patterns for the effect of 0.4 mmol L−1 MeJA and 2 mmol L−1 SA treatments on BRI, LD and seven fruit measures (fruit firmness (FF), lignin content (LC), total soluble phenol content (TSPC), total antioxidant capacity (TAC) and enzyme activities of PAL, POD and SOD) in treatments of M. laxa-inoculated versus (vs.) non-inoculated fruits over an eight-day shelf-life storage period; and (iii) to determine inter-correlations among the seven fruit measures for MeJA and SA treatments. Both MeJA and SA significantly reduced BRI and LD. LC, FF, TAC, TSPC, as well as SOD and PAL activities in the MeJA and SA treatments were higher than the water-treated control in most assessment days and both inoculation treatments. In both inoculation treatments, the activity of POD in the SA-treated fruits was higher than MeJA-treated and control fruits at all dates. In MeJA vs. SA and inoculated vs. non-inoculated treatments, six variable pairs (FF vs. TSPC, FF vs. TAC, TAC vs. PAL, PAL vs. POD, PAL vs. SOD, and POD vs. SOD) showed significant inter-correlation values. Principal component analyses explained 96% and 93% of the total variance for inoculated and non-inoculated treatments, respectively. In inoculated treatments, both PC1 and PC2 explained 41% of the total variance and correlated with FF, TSPC and TAC and with PAL, SOD and POD, respectively. In non-inoculated treatments, PC1 and PC2 explained 49% and 44% of the total variance and correlated with LC, PAL, POD and SOD and with FF, TSPC and TAC, respectively. It can be concluded that MeJA and SA are useful in the practice to enhance the plant defense system against brown rot by reducing fungal growth and by improving physical and antioxidant attributes (FF, LC, TAC and TSPC) and the activity of defense-related enzymes (PAL, POD and SOD) in apricot fruits during shelf-life storage conditions.

Salicylic acid inhibits the postharvest decay of goji berry (Lycium barbarum L.) by modulating the antioxidant system and phenylpropanoid metabolites

Goji berry is a perishable fruit after harvest. To explore the biochemical and molecular mechanisms by which salicylic acid (SA) suppresses rot in goji berry, the fruit was treated with SA and stored for 30 d. Compared with the control, the SA-treated fruit showed smaller lesion areas during storage at 20 °C. During storage at 0 °C, the O2∙¯ production and H2O2 levels were lower in SA-treated fruit, although the H2O2 content was higher at the beginning of storage. SA induced the activities and gene expressions of the key proteins (SOD, CAT, APX and POD) associated with redox homeostasis. Simultaneously, the activities and gene expressions of PAL, C4H, 4CL, CHS, CHI and CAD in phenylpropanoid metabolism was activated. Moreover, the production of chlorogenic acid, ferulic acid, p-coumaric acid, sinapic acid, protocatechuic acid, naringenin, and rutin were stimulated to maintain the higher levels by the most effective SA treatment (2 mmol L−1). The results indicate that SA inhibits rot of goji fruit during storage by mediating the antioxidant system and phenylpropanoid metabolism.

Treatment with exogenous salicylic acid maintains quality, increases bioactive compounds, and enhances the antioxidant capacity of fresh goji (Lycium barbarum L.) fruit during storage

Goji fruit is susceptible to rot and deterioration after harvest, but drying results in the loss of functional components. To explore the effects of salicylic acid (SA) on fruit quality, bioactive compounds, and antioxidant capacity during storage, fresh goji fruit was treated with SA (1, 2, and 3 mmol L−1) and stored at 0 °C or ambient temperature. Compared to the control, SA repressed disease at both treatment temperatures. During storage at 0 °C, SA decreased respiration intensity and ethylene production and resulted in higher color values, firmness, total soluble solids (TSS), and TSS-to-titratable acidity ratio compared to the control. Meanwhile, the SA-treated fruits showed lower weight loss, lower titratable acidity, and better sensory quality. Treated fruit stored at 0 °C also showed higher hydrophilic and lipophilic total antioxidant activities compared to the control, which was attributed to the higher contents of hydrophilic bioactive components (e.g., ascorbic acid, total phenolics, and total flavonoids) and lipophilic bioactive components (e.g., total carotenoids). Among the tested SA concentrations, 2 mmol L−1 SA had the strongest effects. The results demonstrate that SA can delay ripening and senescence, retain fruit quality, promote the accumulation of bioactive compounds, and enhance the antioxidant capacity of fresh goji fruit during storage.

Temporal Changes and Correlations between Quality Loss Parameters, Antioxidant Properties and Enzyme Activities in Apricot Fruit Treated with Methyl Jasmonate and Salicylic Acid during Cold Storage and Shelf-Life

The apricot storability is one of the largest challenges, which the apricot industry has to face all over the world; therefore, finding options for prolonging fruit quality during cold storage (CS) and shelf-life (SL) will help to decrease postharvest losses of apricot. The aim of this apricot fruit work was to study the temporal changes and correlations of 10 quality parameters (quality losses, antioxidant properties and enzyme activities) in the postharvest treatments of methyl jasmonate (MeJA) and salicylic acid (SA) under 1 °C CS (7, 14 and 21 days) and 25 °C SL (4 and 8 days after the 21-day CS) treatments. MeJA and SA significantly decreased the quality loss of chilling injury (CI) and fruit decay (FD) at all dates for both storage conditions. MeJA- and SA-treated fruits increased total antioxidant capacity (TAC), total soluble phenolic compounds (TSPC) and carotenoids contents (TCC) at all dates of both storage treatments. In contrast, the ascorbic acid content (AAC) increased only until days 14 and 4 in the CS and SL treatments, respectively. Among enzyme activity parameters, the activities of phenylalanine ammonia-lyase (PAL), peroxidase and superoxide dismutase (SOD) were significantly increased in the MeJA and SA treatments in all dates of both storage treatments. Catalase (CAT) activity increased in the SA and control treatments, while it decreased in the MeJA treatment in both storage conditions. In both the MeJA and the SA treatments, six pair-variables (FD vs. CI, PAL vs. CAT, PAL vs. SOD, TAC vs. SOD, TAC vs. FD, and AAC vs. CI) were significant in Pearson correlation and regression analyses among the 45 parameters pairs. Principal component analyses explained 89.3% of the total variance and PC1 accounted for 55.6% of the variance and correlated with the CI, FD, TAC, TSPC, TCC, PAL and SOD, indicating strong connections among most parameters. In conclusion, MeJA and SA are practically useful and inexpensive techniques to maintain quality attributes of CI, FD, TAC, TSPC, TCC, PAL, POD and SOD in apricot fruit during both CS and SL conditions.

Pre-véraison treatment of salicylic acid to enhance anthocyanin content of grape (Vitis vinifera L.) berries.

Grape berries produce significant amounts of phenolic compounds. These are an essential qualitative factor due to their nutritional value and effect on berry color and texture. Salicylic acid (SA) and its derivatives usually lead to enhancement of phenolic content in plant tissues. The present study was conducted to evaluate the effect of different levels of SA (0.0, 50.0, 100.0, and 200.0mM) on the production of phenolic compounds and the derivatives (anthocyanin and flavonoid) in the grape berries, with emphasis on malvidin-3-O-β glucoside as a regular anthocyanin in red grapes. The results showed that total phenolics content were significantly enhanced in SA-treated (100.0 and 200.0mM) berries compared to untreated ones. Salicylic acid treatment at all concentrations considerably improved the anthocyanin content in the berries and, compared with untreated berries, the accumulation of malvidin-3-O-β glucoside was higher in SA-treated fruits. In particular, the 200.0mM concentration caused approximately two times more malvidin-3-O-β glucoside than the control. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging capacity of the fruits treated with SA were significantly higher than those of the untreated berries. The activity of phenylalanine ammonia-lyase (PAL) in SA treated fruits significantly increased as compared with the untreated clusters. A general evaluation of the current results leads us to the conclusion that SA is a suitable and recommendable treatment for improving and increasing the phenolic and antioxidant capacity of grape berries. Spraying grape berries at pre-véraison stage with SA could therefore be a convenient strategy to increase quality and nutritional value of grape berries considerably. © 2019 Society of Chemical Industry.

Salicylic-Acid-Induced Chilling- and Oxidative-Stress Tolerance in Relation to Gibberellin Homeostasis, C-Repeat/Dehydration-Responsive Element Binding Factor Pathway, and Antioxidant Enzyme Systems in Cold-Stored Tomato Fruit.

Effects of salicylic acid (SA) on gibberellin (GA) homeostasis, C-repeat/dehydration-responsive element binding factor (CBF) pathway, and antioxidant enzyme systems linked to chilling- and oxidative-stress tolerance in tomato fruit were investigated. Mature green tomatoes (Solanum lycopersicum L. cv. Moneymaker) were treated with 0, 0.5, and 1 mM SA solution for 15 min before storage at 4 °C for 28 days. In comparison to 0 or 0.5 mM SA, 1 mM SA significantly decreased the chilling injury (CI) index in tomato fruit. In the SA-treated fruit, the upregulation of GA biosynthetic gene (GA3ox1) expression was followed by gibberellic acid (GA3) surge and DELLA protein degradation. CBF1 participated in the SA-modulated tolerance and stimulated the expression of GA catabolic gene (GA2ox1). Furthermore, 1 mM SA enhanced activities of antioxidant enzymes and, thus, reduced reactive oxygen species accumulation. Our findings suggest that SA might protect tomato fruit from CI and oxidative damage through regulating GA metabolism, CBF1 gene expression, and antioxidant enzyme activities.

Salicylic acid treatment reduces the rot of postharvest citrus fruit by inducing the accumulation of H2O2, primary metabolites and lipophilic polymethoxylated flavones

To comprehensively analyze the effects of salicylic acid (SA) on the storability of Satsuma mandarin (Citrus unshiu), fruits were treated with 2mM SA. The disease incidence of control/SA-treated fruit at 50d and 120d after treatment was 23.3%/10% and 67.3%/23.3%, respectively, suggesting that SA treatment can significantly reduce the rot rate of postharvest citrus fruit. Fruit quality assays revealed that the treatment can maintain fruit firmness without affecting the inner quality. Furthermore, the contents of H2O2 and some defense-related metabolites, such as ornithine and threonine, in citrus pericarp, were significantly increased by SA treatment. Moreover, it was lipophilic polymethoxylated flavones, rather than flavanone glycosides, that accumulated in SA-treated fruits and these can directly inhibit pathogen development. These results suggest that the effects of SA on postharvest citrus fruit may be attributed to the accumulation of H2O2 and defense-related metabolites.

Impact of staggered treatments of novel molecules and ethylene absorbents on postharvest fruit physiology and enzyme activity of ‘Santa Rosa’ plums

The present investigation was conducted to study the effect of staggered removal of cold stored (2°C) plums at 7, 14 and 21 days interval and their subsequent treatment with salicylic acid (SA), nitric oxide (NO) and ethylene absorbent (EA) sachets. The fruit were then stored at supermarket conditions (20±1°C and 90±5% RH) with the objective to know whether delayed EA, SA and NO treatments still have significant beneficial effects on the plum fruit quality. The observations on different physiological and biochemical parameters were taken at 2 days interval. The results showed that staggered treatments enhanced postharvest life and maintained fruit quality. We observed that SA-treated plums showed the highest fruit firmness and lowest decay losses when plums were either removed on 7th, 14th or 21st days of cold storage. Furthermore, SA-treated fruit exhibited lowest rates of respiration and ethylene evolution; phenylalanine ammonia lyase and pectin methyl esterase activities; minimum malondialdehyde content and lowest electrolyte leakage in comparison to those treated either with NO or packed with EA sachets or control fruit. In conclusion, ‘Santa Rosa’ plum removed after 7th (staggered-I), 14th (staggered-II) and 21st day (staggered-III) from cold storage maintained a shelf life of 10, 6 and 4 days, respectively at subsequent supermarket storage conditions. The overall results submit that even if the plums are not treated immediately or within few days after harvest and placed as such in cold store, they can be still treated with SA, NO or in-package ethylene absorbent (EA) treatment for beneficial postharvest influences.

Cold storage in salicylic acid increases enzymatic and non-enzymatic antioxidants of Nam Dok Mai No. 4 mango fruit

The effects of salicylic acid (SA) on reactive oxygen species (ROS) and the antioxidant defence system of mango fruits cv. Nam Dok Mai No. 4 in cold storage were evaluated. Mature mangos were dipped in 1 mM SA and distilled water (as control) for 10 min and stored at 5 1 °C with 90 2% RH for 42 days. Chilling injury (CI) and ROS levels including superoxide radical (O · - 2 ), hydrogen peroxide (H 2 O 2 ) and hydroxyl radical (HO · ) in the exocarp were measured every 7 days. The level of antioxidant system components, viz., enzymatic antioxidants: enzyme activity and gene expression of superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX); and non- enzymatic antioxidants: ascorbic acid, total glutathione and total phenolic contents, total antioxidant capacity (TAC) were determined. In the control fruits, the levels of O · - 2 , H 2 O 2 and HO · increased during storage with a decrease in ascorbic acid and total glutathione contents, while total phenolic content, TAC, enzyme activities, and gene expression of SOD, CAT, and APX increased during the first 21 days of storage but thereafter gradually decreased. CI symptoms appeared in the control fruits on day 21 and rapidly increased thereafter. During storage, SA-treated mango fruits exhibited significantly higher activities of SOD, CAT, and APX; and increased levels of ascorbic acid, total glutathione, total phenolic compounds, and TAC compared to that of the control fruits. High activities of antioxidant enzymes were associated with higher gene expression, which was correlated with the reduction of CI in SA-treated fruits. We conclude that during cold storage, the SA-treatment strengthens the antioxidant defence system reducing CI in mango fruits cv. Nam Dok Mai No. 4 during cold storage.

The role of jasmonic acid and lipoxygenase in propylene-induced chilling tolerance on banana fruit

Banana fruit are sensitive to chilling stress. This study investigated the possible mechanism of propylene-reducing chilling injury (CI) to postharvest banana fruit. Firmness, chromaticity, ethylene production, CI index, electrolyte leakage, lipoxygenases (LOX) activity, contents of jasmonic acid (JA) and salicylic acid (SA) and the expression of genes MaLOX1, MaACS1 and MaACO1 in fruit were examined. The study shows that the propylene treatment delayed CI symptom development and chromaticity change by 2 days. Meantime, the treatment reduced electrolyte leakage, induced LOX activity in the early stage of cold storage and increased JA content in banana peel. SA immersion after propylene treatment improved the SA content in banana peel, but inhibited the LOX activity and JA content increasing, resulting in CI symptom as serious as that of untreated controls. Expression of genes MaLOX1, MaACS1 and MaACO1 in banana fruit was enhanced by propylene treatment. But no significant differences were observed in firmness, ethylene production, MaLOX1, MaACS1 and MaACO1 expression levels between propylene and propylene SA-treated fruit. These results indicated that the LOX activity increasing and JA burst in the early stage of cold storage may play a key role in tolerance the chilling stress in banana fruit.

Effect of 1-MCP and Salicylic Acid on Sugars, Organic Acids and Amino Acids in Peach Fruit during Postharvest Ripening

The present study investigated the influence of 1-methylcyclopropene (1-MCP) and salicylic acid (SA) on sugars, organic acids and amino acids in peach (Prunus persica (L.) Batsch cv. Okubao) during postharvest ripening. The results of principal components analysis (PCA) showed 1-MCP increased the levels of fructose, sucrose, glucose and inositol, but decreased citric acid and oxalic acid levels, whereas no significant difference was observed in SA-treated fruit compared with controls. The result of partial least square regression (PLSR) showed that glucose and asparagine were shown to be strongly correlated with sensory sweetness, sweetness/sourness ratio and overall flavor, whereas sucrose and inositol were significant positive correlated with sourness of peach fruit.

Salicylic acid alleviated pathogen-induced oxidative stress in harvested sweet cherry fruit

The role of exogenous salicylic acid (SA) in regulating an antioxidative defense response of sweet cherry ( Prunus avium L. cv. Hongdeng) fruit inoculated with Penicillium expansum was investigated by immunodetection of carbonylated proteins. After inoculation with P. expansum, carbonylated proteins accumulated to a lesser extent in SA-treated fruit than in control fruit, ranging from molecular mass 29–45 kDa. Higher activities of catalase (CAT), glutathione peroxidase (GPX), chitinase and β-1,3-glucanase were observed in SA-treated fruit. Similarly, the expressions of CAT, GPX and β-1,3-glucanase genes were also stimulated by SA treatment. Moreover, 2 mM SA did not inhibit P. expansum growth in vitro. These results indicate that SA activated antioxidant defense responses of sweet cherry fruit, which may play a role in the resistance against P. expansum.

Enhancement of Postharvest Disease Resistance in Ya Li Pear (Pyrus bretschneideri) Fruit by Salicylic Acid Sprays on the Trees during Fruit Growth

The Ya Li pear (Pyrus bretschneideri) trees were sprayed three times with 2.5 mM salicylic acid (SA) around 30, 60 and 90 days after full flowering. The fruit were harvested at commercial maturity (about 120 days after full flowering), inoculated with Penicillium expansum, and incubated at 20 °C, 95–100% RH. The results showed that resistance to the pathogen of the mature pear fruit was remarkably enhanced by the SA sprays. Disease incidence in the SA-treated fruit was 58.0% or 26.5%, and lesion diameter on SA-treated fruit was 58.4% or 29.0% lower than that in/on fruit without SA treatment (control) on day 12 or 17 after incubation, respectively. The SA spray applied to the trees around 30 days after full flowering notably enhanced accumulation of hydrogen peroxide in the young fruit. Meanwhile, activities of defense enzymes, including peroxidase, phenylalanine ammonia-lyase (PAL), chitinase or β-1,3-glucanase in the young fruit from SA-treated trees was 29.5%, 60.0%, 24.4% or 35.7% higher than that in the control fruit 4 days after the SA spraying. Furthermore, after harvest, activities of PAL, chitinase and β-1,3-glucanase were still significantly higher in the mature pear fruit from the trees sprayed three times with SA than those of the control fruit. Activities of the antioxidant enzymes including catalase and ascorbate peroxidase in the young fruit were significantly reduced by SA spraying. However, the activity of another antioxidant enzyme, glutathione reductase in the young fruit was significantly enhanced by SA spraying. These results suggest that enzymes exerting their functions in different ways may be coordinately regulated by SA in the pear fruit. Our study indicates that treatment of SA sprays on the trees may provide further protection against postharvest disease of Ya Li pear fruit in practice and could be used as an alternative and economical approach to reduce application of chemical fungicides.

Induction of H 2O 2-metabolizing enzymes and total protein synthesis by antagonistic yeast and salicylic acid in harvested sweet cherry fruit

The immersion of sweet cherry fruit in Pichia membranefaciens at a concentration of 5 × 10 7 cells ml −1 or in salicyclic acid (SA) at 0.5 mM for 10 min reduced the incidence of decay and lesion size caused by Penicillium expansum. Without pathogen inoculation, peroxidase (POD) activity was enhanced in yeast-treated fruit, but activities of catalase (CAT) and superoxide dismutase (SOD) showed a decrease in the same fruit. SA-treatment significantly inhibited CAT activity, but stimulated SOD and POD activities. After inoculation with P. expansum, CAT activity decreased and SOD activity increased in both yeast- and SA-treated fruit. No obvious difference was found in POD activity between treatments and water control. Treatments with yeast and SA changed the expression of POD isozymes. In addition, yeast and SA treatment increased total protein content of sweet cherry and up-regulated 33 and 47 kDa protein bands shown by SDS-PAGE. These results indicated that yeast- and SA-treatments induced synthesis of anti-oxidant enzymes and specific proteins, which may play a role in the resistance against postharvest blue mold.