Incidence Of Superficial Scald Research Articles

Effect of repeated low oxygen stress (RLOS) on superficial scald incidence on ‘Packham’s Triumph’ pears

Effect of repeated low oxygen stress (RLOS) on superficial scald incidence on ‘Packham’s Triumph’ pears

Antioxidants of blushed and unblushed sides in relation to superficial scald of ‘NY2’ (RubyFrost®) apples treated preharvest with 1-methylcyclopropene and aminoethoxyvinylglycine

The effects of plant growth regulators (PGRs) and harvest date on antioxidant contents at harvest and superficial scald development in ‘NY2’ apple during storage have been studied. Aminoethoxyvinylglycine (AVG, ReTain®) and 1-methylcyclopropane (1-MCP, Harvista™) were sprayed two and one weeks, respectively, before the first of three weekly harvests. The apples were stored at 0.5 °C for 20 weeks + 7 d at 20 °C. At harvest, color and index of absorbance difference (IAD) values, and contents of total phenolics, anthocyanins, chlorophylls, carotenoids, ascorbic acid (TAA), dehydroascorbic acid (DHA) glutathione (GSH), reduced glutathione (GSSG) and total antioxidant activity of blushed and unblushed sides of the apple were measured. The antioxidant contents increased with later harvest dates. Chlorophyll and GSSG were higher in unblushed than blushed skin tissues, while all antioxidant contents were highest in blushed skin tissues. Superficial scald incidence was highly correlated with less mature fruit, lower fruit anthocyanin, higher chlorophyll content at harvest. α-Farnesene, conjugated trienols (CTols), and IAD value index were measured at 0, 1, 2, 4, 6, 10, 15, and 20 weeks at 0.5 ⁰C for fruit from harvest 1. Scald incidence and severity was higher in AVG-treated fruit than untreated or 1-MCP treated fruit and did not decrease at later harvest dates. Using harvest management and preharvest application of plant growth regulators is a promising strategy to improve the nutritional value of 'NY2′ apples, reduce physiological disorders, and maintain fruit quality.

A hydroxypropyl methylcellulose (HPMC)-based coating inhibits ethylene-dependent quality changes and reduces superficial scald incidence and blue mould severity during postharvest handling of two apple varieties

The search of new alternatives to substitute postharvest treatments based on synthetic chemicals has gained attention on recent years due to social pressure and stricter legislative policies. Consequently, edible coatings from natural sources have risen as potential solutions to retain postharvest fruit quality. Among these, coatings based on hydroxypropyl methylcellulose (HPMC) have shown potential in preserving fruit quality after harvest. However, scarce studies have explored into their effects on the physiology of climacteric fruits. In this context, the effect of a novel HPMC-based edible coating on fruit postharvest physiology and quality was evaluated in two apple cultivars: ‘Golden Reinders’ and ‘Granny Smith’. In both cultivars, the HPMC-based coating was able to preserve some initial quality attributes, such as firmness and colour, while reducing superficial scald and the severity of blue mould caused by Penicillium expansum. Coated fruit showed reduced ACS activity and ethylene production, delaying changes in ethylene-dependent parameters such as colour and firmness during two different postharvest scenarios: shelf life after harvest and after 3 months of cold storage. Other ripening-associated traits such as starch index, soluble solids content (SSC), and total titratable acidity (TTA) were not affected by the coating application. The coating altered the levels and composition of volatile organic compounds (VOCs), yet without affecting the overall consumer acceptance in most of the studied scenarios. Changes in fruit physiology promoted by the coating, including the decrease of α-farnesene levels and its oxidation products, together with enhanced accumulation of ethanol may reduce the superficial scald incidence in ‘Granny Smith’ and the severity of blue mould rot in the two studied cultivars. Overall, the use of the HPMC-based coating in apples could be useful for maintaining fruit quality and reducing postharvest losses related to mould development and physiological disorders without compromising taste perception.

Metabolome and transcriptome profiling in different bagging pear fruit reveals that PbKCS10 affects the occurrence of superficial scald via regulating the wax formation.

Superficial scald is a physiological disorder of fruit, which is easy to occur during long-term cold storage after harvest. Different preharvest bagging treatments (no bagging, polyethylene bagging and non-woven fabric bagging) were used to explore the occurrence mechanism of superficial scald. UHPLC-MS analysis, GC-MS analysis and RNA-seq revealed the influence of the wax of 'Chili' on the occurrence of superficial scald. The wax content and wax components (Lupeol, lup-20(29)-en-3-one, heptacosane, 9-octadecenoic acid, eicosanoic acid, cis-11-eicosenoic acid) were significantly higher in the fruit bagged with non-woven fabric (NWF, with low incidence of superficial scald) than that in fruit bagged with polyethylene (PE, high incidence of superficial scald). Transcriptomics and qRT-PCR data identified a wax synthesis gene, PbKCS10, which exhibited high expression levels in fruit with low of superficial scald. The results of gene function showed that PbKCS10 reduced the occurrence of superficial scald by increasing the wax formation.

Superficial scald development in ‘Granny Smith’ and ‘Nicoter’ apples: The role of key volatile compounds when fruit are stored under dynamic controlled atmosphere

A positive correlation of α-farnesene and its oxidation metabolites with superficial scald is commonly reported in apples stored in air or controlled atmosphere (CA) systems, where O2 levels are above the lower oxygen limit (LOL) tolerated by the fruit. Nevertheless, the LOL can be monitored by the dynamic controlled atmosphere (DCA) techniques and to provide different physiological responses. Therefore, this study aimed to evaluate key volatile metabolites from ‘Granny Smith’ and ‘Nicoter’ (‘Kanzi®’) apples stored under dynamic controlled atmosphere (DCA) monitored by respiratory quotient (RQ), i. e. at extremely low oxygen partial pressures (ELO) and correlate their emissions with the incidence of superficial scald (SS). The volatile compounds (VCs) were isolated by solid phase microextraction (HS-SPME) and analyzed by gas chromatography. For the first time, higher concentrations of α-farnesene and its oxidation metabolites (6-methyl-5-hepten-2-one, and 6-methyl-5-hepten-2-ol) were negatively correlated with SS in DCA-RQ. This is likely due to the higher levels of ethanol in fruit stored under this condition having an inhibitory effect on SS incidence even when α-farnesene, 6-methyl-5-hepten-2-one, and 6-methyl-5-hepten-2-ol accumulate. Additionally, SS is more correlated to internal ethylene concentration (IEC) than α-farnesene accumulation and their metabolites, even when fruit were stored under ELO, where ethylene action is reduced.

Pb4CL2 Inducing Lignin Accumulation in Superficial Scald ‘Chili’ (Pyrus bretschneideri) Pear Fruit

Superficial scald of pear fruit is a physiological disorder that easily occurs during cold storage and seriously affects pear eating quality and commodity value. It is important to study the mechanism of superficial scald disorder. Our previous study reported that the incidence of superficial scald of calcium chloride (CaCl2)-treated pear fruit during storage was significantly lower than that of untreated fruit. In this study, we found that the accumulation of lignin in CaCl2-treated fruit was significantly lower than that of untreated fruit. The expression of the Pb4CL2 gene in the lignin synthesis pathway was downregulated in the CaCl2-treated fruit. The lignification level of the fruit overexpressing Pb4CL2 was significantly higher than that of the empty vector fruit. Therefore, we speculate that downregulation of Pb4CL2 after CaCl2 treatment plays an important role in CaCl2 inhibiting superficial scald disorder by affecting lignin accumulation in pear fruit.

Transcription factor MdLSD1 negatively regulates α-farnesene biosynthesis in apple-fruit skin tissue.

α-Farnesene is a sesquiterpene present in plants. It was first discovered in apples. It plays an important role in the plant defence response and is considered a key factor in the occurrence of superficial scald. The gene encoding α-farnesene synthase, which is the last key enzyme in the biosynthetic pathway of α-farnesene in apple fruit, hasbecome the primary target enzyme for controlling the genetic manipulation of α-farnesene biosynthesis. In this study, the yeast one-hybrid assay and the dual luciferase assay were used to ascertain the relationship between MdLSD1 and MdAFS. Real-time PCR was used to analyse the molecular mechanism underlying the regulation of MdAFS by MdLSD1. Our results revealed that transcription factor MdLSD1, which is closely related to programmed cell death in apple fruit tissues, binds to MdAFS. Transient transformation of apple skin with vectors overexpressing MdLSD1 showed that the gene negatively regulates MdAFS. Overall, we suggest that MdLSD1 negatively regulates MdAFS. Our results are of great significance for future research on the transcriptional regulation of the α-farnesene synthase gene and provide a new direction for exploring the specific mechanism of programmed cell death involved in superficial-scald incidence.

Effects of 1-methylcyclopropene and gaseous ozone on Listeria innocua survival and fruit quality of Granny Smith apples during long-term commercial cold storage

This study evaluated the impact of 1-methylcyclopropene (1-MCP), an ethylene synthesis inhibitor, followed by long-term commercial cold storage with low-dose gaseous ozone on the microbiological safety and quality of fresh apples. Granny Smith apples were inoculated with or without Listeria innocua, treated with or without 1.0 mg/L 1-MCP for 24 h, then subjected to commercial cold storage conditions including refrigerated air (RA, 0.6 °C, control), controlled atmosphere (CA, 2% O2, 1% CO2, 0.6 °C), and CA with 51–87 μg/L ozone gas for up to 36 weeks. RA storage reduced L. innocua on apples by up to 3.6 log10 CFU/apple. CA had no advantage over RA in controlling Listeria. Continuous ozone gas application resulted in an additional ∼2.0 log10 CFU/apple reduction of L. innocua (total reduction up to 5.7 log10 CFU/apple) and suppressed native bacteria and fungi. Treatment with 1-MCP had a minor impact on survival of L. innocua or background microbiota on apples, while it significantly delayed fruit ripening and reduced the incidence of superficial scald and internal browning. In summary, 1-MCP treatment followed by CA storage with low-dose continuous ozone gas can effectively control Listeria on fresh apples and delay fruit ripening.

Management of ethylene production, superficial scald and fruit quality in ‘Granny Smith’ apple using organic oils and ozonised cold storage

Ethylene management during storage of organically grown apples is challenging due to limited number of treatment and storage options that are available for organic produce. In this study the effects of fumigation with lemon and cinnamon oils on ethylene production, superficial scald incidence, and fruit quality in 'Granny Smith apples' placed in cold storage with and without application of ozone were evaluated. The fruit were fumigated with 3 µL L‑1 lemon or cinnamon oil for 24 h while untreated fruit were used as a control. Following the treatments, the fruit were put into cold storage at 0±2, with and without ozone for 100 or 150 days. After each storage period, ethylene production, superficial scald incidence, and fruit quality parameters were recorded. The fruit fumigated with lemon oil was significantly reduced climacteric ethylene peak rates after 100 and 150 days cold storage. The mean rate at which the ethylene climacteric peak developed was significantly reduced in fruit stored in ozonised cold storage compared to the peak level in fruit stored without ozone for 100 days. The climacteric ethylene peak was significantly delayed in the fruit cold stored with ozone (8.78 d) as compared to without ozone (3.89 d) following 100 days storage. Fruit firmness was significantly higher in fruit fumigated with lemon or cinnamon oil compared to control fruit for both storage times. Lemon or cinnamon oil fumigation significantly reduced superficial scald in the cold-stored fruit with or without ozone. The fruit fumigated with lemon oil or cinnamon oil following 150 days cold storage resulted in significantly higher levels of ascorbic acid and antioxidant capacity compared to control fruit. Overall, lemon oil fumigation was more effective in suppressing ethylene production in 100 and 150 day cold-stored fruit than cinnamon oil. Notably, fumigation with lemon or cinnamon oil were effective in reducing superficial scald and maintaining quality in 100 and 150 days cold-stored fruit.

Investigation of proline in superficial scald development during low temperature storage of ‘Dangshansuli’ pear fruit

The role of proline in superficial scald development in pear fruit was investigated in this study. During low temperature storage of ‘Dangshansuli’ pear fruit, superficial scald incidence and index accumulated in association with the alternation of α-farnesene and conjugated trienols (CTols). 14 out of 17 free amino acids were identified; proline content gradually decreased, which was consistent with the up-regulation of PbrP5CS activity and down-regulation of PbrProDH activity in its metabolic pathway. A total of 14 genes involved in proline metabolism were identified based on transcriptome annotation with diverse expression profiles. Results from correlation analysis among proline content further indicate that enzyme activity and gene expression profile, PbrProDH2, PbrProDH4, PbrProDH5 &PbrP5CS5 might play a critical role in proline metabolism during low temperature storage of ‘Dangshansuli’ fruit; thus, influencing superficial scald development which was then functionally validated using the transgenic pear fruit. Postharvest 1-MCP and diphenylamine (DPA) treatment inhibited the accumulation of CTols, and thus, mitigated superficial scald development and maintained higher proline content, in association with the up-regulated PbrP5CS activity, PbrP5CS4 &PbrP5CS5 mRNAs as well as the down-regulated PbrProDH activity &PbrProDH4 transcripts. In a further study, we found that exogenous application of proline alleviated superficial scald incidence and index. To that end, the results of our study confirmed that proline was involved in superficial scald development during pear storage.

Influence of Different Calcium Compounds and Fruit Development Stages on Yield, Fruit Quality and Shelf Life of ‘Granny Smith’ Apples

Calcium (Ca) plays major roles on the storage life and quality apples. In this study, the influence of calcium chloride (CaCl2) and two organic calcium compounds including Calcicat and Folical at four different times of application on the quality and shelf life of ‘Granny Smith’ apples during two growing seasons. Quantitative and qualitative attributes were evaluated at harvest and after three- and six-months cold storage. In the first year, Folical all-season and mid-season sprays resulted in a significant increase in Ca concentration. In the second year, early-season spray resulted in significant Ca increase compared to control. In the first year, the early-season spray program of Folical had the highest yield and fruit weight. The use of calcium compounds in all timing programs reduced fruits soluble solids concentration (SSC) at harvest compared to control treatments. In both years, at harvest, no significant difference was observed among treatments regarding the ‘Granny smith’ apple firmness. In the first year, the chlorophyll content of ‘Granny Smith’ apple peels were affected by spray timing and the type of calcium compound. In both years, Fruits treated with Ca had lower ethylene concentration and brightness index (L*) than controls. In the second year, Folical spray decreased the percentage of superficial scald incidence for three months storage. During the first year, all-season Calcicat spray and in the second year early-season Folical spray showed the lowest percentage of scald disorder after six months storage. In the first year, the all-season spray program and in the second year Folical spray decreased the severity of scald after three months of storage.

Unravelling the cold-induced regulation of ethylene and α-farnesene and its involvement with the development of scald-like disorders in different pear cultivars

To better understand the cold-induced regulation of scald-like disorders in pears and the specific roles played by ethylene and α-farnesene, three pear cultivars with different patterns of ethylene production and chilling requirement were used in this study. Fruit were treated with 1-MCP (ethylene inhibitor) and Lovastatin (α-farnesene inhibitor) and stored at -0.5 °C and 90 % RH during 6 months. Changes in targeted metabolites, enzymes and genes were monitored periodically up to 120 d of storage and superficial scald incidence was assessed after this time and after 180 d of cold storage. 1-MCP treatment induced in the three cultivars a down-regulation of PcACS1, PcACO1, PcERF1 and PcAFS1 gene expression, but also a significant up-regulation of PcETR1 and PcEIN2 that led in all cases to the inhibition of the disorder incidence. In contrast, Lovastatin treatment caused diverse molecular or biochemical responses depending on the cultivar. In ‘Blanquilla’ pears, this treatment completely inhibited superficial scald reinforcing the idea that ethylene-α-farnesene interaction plays a decisive role in this specific cultivar. In contrast to 1-MCP, Lovastatin treatment did not control the disorder incidence in ‘Flor d’Hivern’ pears. Inversely, 1-MCP inhibited the development of the disorder, showing then that the inhibition of ethylene biosynthetic and signalling pathway may control superficial scald even in cultivars producing very low or undetectable ethylene levels. Finally, the inefficacy of both treatments to prevent the disorder development in ‘Conference’ pears, suggests the existence of a disorder different from that observed for the other cultivars whose biochemical basis remain unknown. Collectively our results show that the regulatory processes triggered by cold stress in pears are complex and cultivar dependent.

Understanding the key preharvest factors determining ‘Packham’s Triumph’ pear heterogeneity and impact in superficial scald development and control

Abstract Although superficial scald (SS) is well characterized on apples, there is still few information regarding the influence that initial fruit’s maturity heterogeneity may have on the development of this disorder on pears. In this study we aimed to understand the effect of growing season and site, harvest maturity, and their interaction with postharvest treatments on superficial scald development. Pears (Pyrus communis L.) cv ‘Packham’s Triumph’ were picked during three consecutive seasons at three harvest maturities (H1, H2, H3) from different commercial orchards. Different SS control treatments (DPA vs. 1-MCP; season # 2) and storage scenarios (RA, CA and RA + stepwise cooling (SWC); season # 3) were evaluated. Bioclimatic indices, superficial scald incidence, maturity indices and biochemical analysis associated with SS were carried out at harvest and periodically postharvest in all treatments. In general, bioclimatic indexes (GDA and HL10) were poorly correlated with SS incidence. Only in season #1, harvest maturity was positively correlated with SS after 140 and 180 d into storage (rs = 0.621* and 0.620*, respectively), the more mature fruit being more sensitive. The opposite was observed in season #3, and no pattern in season #2. There was a good and positive correlation between CTols dynamic (δCTols/δt) and SS development, with variation between seasons. DPA and 1-MCP effectively reduced SS up to 180 d regardless of years and orchard location. In contrast, the beneficial effect of CA storage was orchard dependent and SWC strategy did not control SS and affected fruit quality. Collectively our results suggest that initial fruit heterogeneity at harvest is an important factor that modulate SS development in ‘Packham triumph pears. Climatic and fruit maturity indexes are not reliable for a multi-year prediction of SS development. In contrast to CA storage that reduced the disorder in an orchard dependent manner, 1-MCP and DPA treatments effectively controlled SS independently of initial fruit heterogeneity.

Aloe vera gel coating aggravates superficial scald incidence in ‘Starking’ apples during low-temperature storage

The effects of aloe vera (Aloe vera (L.) Burm. f.) gel treatment on the incidence of superficial scald in ‘Starking’ apples (Malus domestica Borkh. Var. Starking) during cold storage were studied. Apples were harvested at the pre-climacteric stage and treated with aloe vera gel. The treatment increased malondialdehyde content and membrane lipid damage. Furthermore, it inhibited the release of ethylene at the early stage but increased it in the later stage. The expression level of ACC synthase 1 (MdACS1) also increased, and the antioxidant capacity in apples, particularly, catalase, peroxidase, and superoxide dismutase activities, all decreased, while concomitantly, the content of α-farnesene and its oxidation product, conjugated triene increased, thereby aggravating superficial scald incidence during storage at low temperature.

Ripening behavior and quality of 1-MCP treated d'Anjou pears during controlled atmosphere storage

1-Methylcyclopropene (1-MCP) inhibits ethylene production and development of superficial scald, thus leading to varied ripening capacity of d'Anjou pears (Pyrus communis L.). When exposed to elevated storage temperature, 1-MCP-treated fruit ripens normally but loses its green peel color. This study investigated the effect of 1-MCP treatment and postharvest storage conditions on storage quality and ripening capacity of d'Anjou pears harvested at commercial maturity for 8 months at 1.1 °C. Fruits with 1-MCP treatment at low O2 resulted in relatively low respiration rate and delayed ethylene production during 8 months of storage. Fruits stored under CA condition with 1-MCP treatment not only showed low incidence of superficial scald and decay but also retained flesh firmness (FF), chlorophyll content (IAD) and hue angle compared with fruits that underwent other treatments during the same storage period. However, about 20% and 15% fruits under 1% O2 condition with 1-MCP treatment developed peel black speck and pithy brown core at the end of storage period, respectively. CA condition with 1-MCP treatment prolonged desirable eating quality of d'Anjou pears with retained titratable acidity and higher sensory score. Pears with or without 1-MCP treatment developed ripening capacity after 6 and 8 months of storage. 1-MCP-treated fruit under CA led to lower respiration and ethylene production rate but higher FF, IAD and hue angle during five days of ripening after long-term storage.

Pre-harvest climate and post-harvest acclimation to cold prevent from superficial scald development in Granny Smith apples

Superficial scald is one of the most serious postharvest physiological disorders that can affect apples after a prolonged cold storage period. This study investigated the impact of pre- and post-harvest climatic variations on superficial scald in a susceptible apple cultivar. Fruit batches with contrasting phenotypes for superficial scald incidence were identified among several years of “Granny Smith” fruit production. The “low scald” year pre-harvest climate was characterised by a warm period followed by a sudden decrease in temperature, playing the part of an in vivo acclimation to cold storage. This was associated with many abiotic stress responsive genes which were induced in fruit peel. In particular 48 Heat Shock Proteins (HSPs) and 5 Heat Shock transcription Factors (HSFs) were strongly induced at harvest when scald incidence was low. For “high scald” year, a post-harvest acclimation of 1 week was efficient in reducing scald incidence. Expression profiles of stress related genes were affected by the acclimation treatment and indicate fruit physiological adaptations to cold storage. The identified stress-responsive genes, and in particular HSPs, could be useful indicators of the fruit physiological status to predict the risk of scald occurrence as early as harvest.

Pre- and Postharvest Factors Control the Disease Incidence of Superficial Scald in the New Fire Blight Tolerant Apple Variety “Ladina”

Superficial scald is a physiological disorder that develops during cold storage affecting apples and causes substantial market losses. Malus × domestica cv. Ladina, a new scab resistant and fire blight tolerant variety, commercialized in 2012, shows a physiological disorder similar to superficial scald after storage. Here, we used different pre- and postharvest approaches to characterize the occurrence of these superficial scald symptoms in Malus × domestica cv. Ladina. Over a period of seven years, fruits from multiple orchards were stored for five to seven months and the occurrence of superficial scald was assessed in fruits after cold storage and controlled atmosphere (CA) storage. Apples picked at different stages of ripeness within the same year differed in superficial scald development. Additionally, superficial scald differed significantly between years and locations, strongly suggesting that maturity at harvest, weather during the growing season, and orchard management play important roles in scald occurrence. Treatment with 1-methylcyclopropene (1-MCP) after harvest, and storage in a dynamically controlled atmosphere (DCA) significantly reduced the occurrence of superficial scald, whereas storage under ultralow oxygen concentrations (ULO) showed mild but not significant effects. Low calcium concentrations in the fruit flesh and peel were associated with stronger superficial scald occurrence.

Preharvest bagging and postharvest calcium treatment affects superficial scald incidence and calcium nutrition during storage of ‘Chili’ pear (Pyrus bretschneideri) fruit

Abstract Superficial scald, which appears as black or brown necrotic patches on the skin, is a serious postharvest physiological disorder of pear fruit. The occurrence of scald in ‘Chili’ pear (Pyrus bretschneideri) fruit during storage at 2 °C in response to preharvest polyethylene (PE) bagging and non-woven fabric bagging has been investigated. The non-woven fabric bagging treatment of fruit prevented scald development, while the PE bagged fruit had a higher incidence of scald than the untreated fruit. Fruit from the PE bagging treatment had lower Ca content, less distribution and lower flux rate of Ca2+ than no bagging and non-woven fabric bagging fruit. The treatment also was associated with greater expression of genes encoding calmodulin-like (CML) proteins, such as PbCML19, PbCML5, PbCML38, PbCML42-1, and PbCML42-2. In contrast, non-woven fabric bagging did not affect the expression of these genes in the fruit. In addition, CaCl2 treatment reduced scald development in PE bagged pear fruit during storage. Our results suggest that Ca2+ may play a role in regulating the occurrence of superficial scald in pear fruit.

Production area and harvest date influence superficial scald incidence and ultra-structure of 'Suli' pear skin during long term storage

The effect of production area and harvest date on the superficial scald incidence, ultra-structure of the pericarp, core browning, and related physical qualities of ‘Suli’ pears during storage period at 0 °C were investigated. ‘Suli’ fruits were harvested at Taigu and Linyi in Shanxi province of China over five different dates and then stored at 0±0.5 °C with 85-90% relative humidity for 120 or 200 days. Superficial scald was detected after 120 and 200 days of storage. Harvest date and production area significantly affected the incidence of superficial scald and the quality of 'Suli' fruits. Earlier harvest time was associated with increased incidence of superficial scald. Fruits picked at Linyi developed more severe superficial scald than fruits harvested at Taigu. Scanning electron microscope (SEM) revealed that the cuticle and wax layer of fruits from Taigu were thicker than those from Linyi after storage. The surface of earlier harvested fruits had less wax and more extensive cracking, lower pectin content, and damaged skin organization structure. The incidence of superficial scald in ‘Suli’ pears is dependent on the ultra-structure of these superficial layers, and differences may be driven by harvest date and location. Keywords: Production area, Harvest date, Superficial scald incidence, Ultra-structure, ‘Suli’ pear

Effect of 1-Methylcyclopropene on Superficial Scald Associated with Ethylene Production, α-Farnesene Catabolism, and Antioxidant System of Over-Mature ‘d’Anjou’ Pears After Long-Term Storage

To optimize storage quality of ‘d’Anjou’ pears (Pyrus communis L.) produced in the US Pacific Northwest regions, the recommended harvest maturity as indicated by flesh pressure is 67 to 58 N. Over-mature pears are more susceptible to superficial scald and inferior eating quality after storage. However, a significant portion of pears is harvested at an over-mature stage due to rapid on-tree maturation during years with labor shortages. 1-Methylcyclopropene (1-MCP) extends storage quality of pears but interferes their ultimate ripening capacity. The purpose of this work was to evaluate the effect of 1-MCP on over-mature ‘d’Anjou’ pears. Fruit from two orchards at fruit firmness (FF) 55.6 and 56.0 N were treated with 0.15 μL L−1 1-MCP, held at − 1.1 °C for up to 7 months. 1-MCP treatment significantly inhibited ethylene synthesis and respiration rate, reduced superficial scald, and maintained high storage quality of over-mature pears from two orchards during 7 months of storage. After 7 months of storage at − 1.1 °C, some of the pears from Orchard 1 recovered ripening capacity after 5 days at 20 °C. The development of superficial scald in over-mature ‘Anjou’ pears was associated with the accumulation of α-farnesene and conjugated trienols (CTols). 1-MCP significantly inhibited the development of scald, perhaps by alleviating membrane lipid peroxidation and enhancing total antioxidant capacity, antioxidant metabolites (i.e., total polyphenols (TP) and total flavonoids (TF)), and related enzyme activities (i.e., superoxide dismutase (SOD), catalase (CAT)) in pear skin. Overall, this study provides the preliminary basis for commercial application of 1-MCP in over-mature pears and demonstrates its potential to maintain fruit quality and reduce the incidence of superficial scald.