Navel Orange Fruit Research Articles

The Role of Protein Contents and Enzyme Activity on Creasing of Washington Navel Orange Fruits

The Role of Protein Contents and Enzyme Activity on Creasing of Washington Navel Orange Fruits

Thiabendazole residue loading in dip, drench and wax coating applications to control green mould and chilling injury on citrus fruit

Green mould (caused by Penicillium digitatum) is a major cause of postharvest losses in citrus. Residue loading of thiabendazole (TBZ) with application methods typically used in South African packhouses and green mould control was studied. TBZ was applied curatively and protectively in dip, drench and wax coating treatments and fruit were inoculated with a TBZ-sensitive or a TBZ-resistant isolate of P. digitatum. The dip treatments consisted of TBZ concentrations of 0–2000μgmL−1; fruit were dipped for 60s at 22°C at a pH of 7. Residues differed between fruit batches and ranged from 0.5 to 1.7μgg−1 at 1000μgmL−1 TBZ. Curative dip treatments almost completely controlled green mould (>96% at 1000μgmL−1 TBZ). The residue level needed for 75% curative control ranged from 0.06 to 0.22μgg−1, depending on citrus type. Protective treatments were unreliable and control varied from 17% to 97.9% at 1000μgmL−1 TBZ between fruit batches. Drench treatments consisted of exposure times of 30, 60 and 90s with 1000 or 2000μgmL−1 TBZ. Average TBZ residues were 2.14μgg−1 for Clementine mandarin fruit and 3.50μgg−1 for navel orange fruit. Green mould control on navel orange fruit resulted in 66–92%, 34–90% and 9–38% control for curative treatments after 6 and 24h and protective treatments, respectively, depending on fruit batch. Wax with 4000μgmL−1 TBZ was applied at 0.6, 1.2 and 1.8Lwaxton−1 fruit. Chilling injury was evaluated after fruit storage at −0.5°C for 40 days. Average TBZ residues loaded was 1.3, 1.3 and 2.7μgg−1 at the recommended 1.2Lton−1 for Satsuma mandarin, Clementine mandarin and Valencia orange fruit, respectively. Protective treatments showed lower infection levels (14–20%) than curative treatments (27–40%) for Valencia orange fruit. The same trend was observed with Satsuma (92–95% curative; 87–90% protective) and Clementine mandarin fruit (82–90% curative; 59–88% protective), but control was relatively poor. TBZ application in wax exceeded 5μgg−1 at higher wax loads (1.2 and 1.8Lton−1). Wax treatments showed a significant reduction in chilling injury; TBZ had an additive effect. TBZ resistant isolates could not be controlled.

The effects of Kloeckera apiculata on the cuticular waxes of navel orange fruit

Kloeckera apiculata 34-9 was selected from the rhizosphere soil for its high efficacy in controlling citrus green and blue mold. In this study, the effect of the antagonistic yeast K. apiculata on citrus cuticular wax was investigated in ripening Newhall navel orange (Citrus sinensis L. Osbeck). Our results show that K. apiculata triggers the production of cuticular waxes and surface wax morphology changes in the fruit surface. 15 K. apiculata-responsive differentially expressed genes (DEGs) were identified for wax metabolism by using the Affymetrix citrus genome GeneChip. Using GC–MS, 46 wax compounds were found in the Newhall fruit surface. On one hand, esters including docosanoic acid, 1,2,3-propanetriyl ester and 9-hexadecenoic acid, 9-octadecenyl ester were up-regulated approximately twofold in the treatment condition compared with the control; and on the other hand, the fatty acids and fatty alcohols decreased by 74.4% and 72.3%, respectively, in the treatment condition. The new wax production and increased hydrophobicity of the Newhall surface resulting from the treatment may influence spore adhesion and germination. Furthermore, the response of the fruit waxes to the K. apiculata stimulus is likely to be regulated by intra-cellular H2O2 signaling. This study demonstrated the response fruit waxes to K. apiculata in Newhall navel oranges, thus providing new clues that aid our understanding of the mechanisms of action of antagonistic yeasts in postharvest fruits.

Use of seaweed extract as a promising post-harvest treatment on Washington Navel orange (Citrus sinensis Osbeck)

Orange is the main fruit crop in Egypt and most varieties are available during winter. Use of hazardous chemicals and their environmental effect has received great attention worldwide. The aim of this study was to substitute chemicals with natural materials as a means to reduce contamination of foods. The present study was carried out in Egypt during 2009 and 2010. Navel orange fruits were sampled and treated with five different post-harvest dipping treatments (control, seaweed extracts at 2% and 4% and calcium chloride at 2% and 4%). One group of each treatment was stored at room temperature (21 ± 2°C and 65–75% RH) for 45 days and the second group was at cold temperature (7°C and 65–75% RH) for 75 days. Soluble solids content, total sugars and reducing sugars content were increased in 4% seaweed extract treated fruit stored either at room temperature or in cold storage. Generally, seaweed extracts are recommended to improve fruit quality and storability of Navel orange fruit, compared with chemicals that are of consumer concern.

Effect of Jojoba Oil and Boric Acid as Postharvest Treatments on the Shelf Life of Washington Navel Orange Fruits

Effect of Jojoba Oil and Boric Acid as Postharvest Treatments on the Shelf Life of Washington Navel Orange Fruits

Storability and quality improvement of Washington Navel orange fruit (Citrus sinensis Osbeck) by safe pre-harvest treatments

Organic sources have received much attention from growers and researchers during the last two decades. Field and laboratory trials suggest that these organic substances have the potential to provide the plant with necessary nutrients, and to improve soil physical and chemical properties as well as to suppress plant disease pathogens and particularly fungal infections. This study was carried out during 2010 and 2011 at Kafr El-Sheikh, Egypt. The effects of pre-harvest foliar sprays with compost tea (CT) or filtered biogas slurry liquid (BSL) at 50% and 100% on storability of Washington Navel orange fruits at room temperature [21 ± 2°C, 65–75% relative humidity (RH)] for 45 days and refrigerated (7°C, 90–95% RH) for 75 days were studied. Most of the four organic spray treatments had a significant effect at most sampling times in reducing fruit decay and weight loss, and maintaining fruit quality. The most effective treatment(s) and the significance of differences between spray treatments varied with parameter measures, season, and storage conditions and time. However, at room temperature, CT 100% was most frequently statistically the best or one of the best treatments followed in order by BSL 100%, CT 50% and BSL 50%. In cold storage, the difference between the organic spray treatments was less clear with all four treatments being statistically the best or equal best for several parameter/season/storage time combinations. Generally, using CT and BSL as natural components to maintain fruit quality and extend storability of Washington Navel orange is more favourable to the consumer.

Assessment of feasibility in determining of Cr in Gannan Navel Orange treated in controlled conditions by laser induced breakdown spectroscopy

Heavy metal element chromium (Cr) contained in Gannan Navel Orange fruits treated with contaminant in controlled lab conditions were analyzed by laser induced breakdown spectroscopy (LIBS) and atomic absorption spectrometry (AAS). The purpose of this work was to provide an assessment of the performance of LIBS in investigating heavy metals in natural organic materials through a direct comparison of the analytical results. The LIBS spectra of samples were collected by optimized experimental parameters and the characteristic spectral lines of two triplet bands at 357.87nm, 359.35nm and 360.53nm and 425.43nm, 427.48nm and 428.97nm were identified distinctly. The Cr I 425.43nm was selected as analytical line. The concentrations of Cr element were determined by AAS. The relative standard deviation (RSD) values were analyzed and the results demonstrated that there are much more room to promote in LIBS measuring. The calibration curve between the LIBS intensity and AAS concentration was constructed about Cr element. The results show LIBS signal intensity linear dependence on the concentration of Cr. Quantitative analytical results by the curve were validated with AAS measurements. The presented results showed that the standard deviations of the LIBS measurements are in general much larger than those of AAS measurements. Mostly, this contributes to matrix effect of samples and instability of LIBS. In a word, the obtained results between LIBS and AAS demonstrate the capacity of LIBS in the determination of the concentrations of Cr in oranges. Further work are being continued in our laboratory for further improvement of the sensitivity of LIBS, and for direct analysis of heavy metals in natural agricultural products without contamination treatment.

Differential Expression of Organic Acid Degradation-Related Genes During Fruit Development of Navel Oranges (Citrus sinensis) in Two Habitats

Organic acids as well as soluble sugars contribute highly to flavor and overall quality of citrus fruit. Citric acid level in fruit is influenced by several factors including environmental conditions. In this study, it was observed that different environments in two habitats (Ganzhou, Jiangxi; Songyang, Zhejiang) had minor effects on total soluble solids and citrus color index but had significant effects on organic acids levels, particularly on citric acid level, in fruit of “Newhall” and “SkaggsBonanza” navel oranges (Citrus sinensis). Expression of genes involved in citric acid biosynthesis and degradation (CitCS1, CitCS2, CitAco1, CitAco2, CitAco3, CitIDH1, CitIDH2, CitIDH3, CitGAD4, CitGAD5, and CitGS2) was analyzed in fruit grown in each of the two habitats. Citric acid biosynthesis-related citrate synthase genes were steadily expressed during navel orange fruit development, while degradation-related genes were differentially expressed. These findings suggested that the influence of different environments on fruit quality traits was predominant on the regulation of organic acids level, particularly on the degradation of citric acid. A cascade of CitAco3–CitIDH1–CitGS2 might be involved in citric acid degradation in response to different environments during fruit growth and development.

Determination of Trace Elements and Rare Earth Elements in Gannan Navel Orange Fruit by ICP-MS

Determination of Trace Elements and Rare Earth Elements in Gannan Navel Orange Fruit by ICP-MS

Imazalil residue loading and green mould control on citrus fruit as affected by formulation, solution pH and exposure time in aqueous dip treatments

Green mould, caused by Penicillium digitatum, is responsible for major postharvest fruit losses on the South African fresh citrus export market. Some of these losses as well as fungicide resistance development can be attributed to sub-optimal imazalil (IMZ) residue loading on citrus fruit (<2μgg−1), which is commonly the case in South African packhouses. This will result in loss of control and sporulation inhibition on decayed fruit. IMZ formulation [IMZ sulphate and emulsifiable concentrate (EC)], solution pH (IMZ sulphate at 500μgmL−1 buffered with NaHCO3 or NaOH to pH 6 and 8) and exposure time (15–540s) were investigated in order to improve IMZ residue loading and the green mould control on Clementine mandarin, ‘Eureka’ lemon, and navel and Valencia orange fruit. Exposure time had no significant effect on residue loading in the unbuffered IMZ sulphate solution (pH 3). No differences were observed between the pH buffers used, but residue loading improved with increase in pH. The maximum residue limit (MRL) of 5.0μgg−1 was exceeded following dip treatment in the IMZ EC (after 75s exposure time), and IMZ sulphate at pH 8 using NaHCO3 (77s) or NaOH (89s) as buffer. The MRL was exceeded after 161s in IMZ sulphate solutions buffered at pH 6 with either NaHCO3 or NaOH. An IMZ residue-loading curve was prepared from which residue levels can be predicted for the control of IMZ-sensitive and IMZ-resistant isolates of P. digitatum. From this model the benchmark residue level for 95% control of an IMZ-sensitive isolate and of an IMZ-resistant isolate were predicted to be 0.81 and 2.64μgg−1, respectively. Residue loading can be improved by adjusting the pH level of an IMZ sulphate solution to 6 or by using the IMZ EC formulation, but exposure time should be restricted to 45s so as not to exceed the MRL. Conversely, sufficient exposure time of ≈90s in an unbuffered IMZ sulphate solution (pH 3) will result to improved green mould control, but with residue loading below 2μgg−1. The resistant isolate could not be controlled adequately with residue levels below the MRL, therewith indicating the practical relevance of IMZ resistance.

A comparison of the ultrastructure and composition of fruits’ cuticular wax from the wild-type ‘Newhall’ navel orange (Citrus sinensis [L.] Osbeck cv. Newhall) and its glossy mutant

The altered ultrastructure and composition of cuticular wax from 'glossy Newhall' (MT) fruits lead to its glossy phenotype. A novel mutant derived from the wild-type (WT) 'Newhall' navel orange (Citrus sinensis [L.] Osbeck cv. Newhall), named 'glossy Newhall' (MT), which produced much more glossy fruits that were easily distinguishable from the WT fruits was characterized in this report. The total wax loads of both WT and MT fruits varied considerably during the fruit development. The most abundant wax fraction of WT mature fruits was triterpenoids, followed by aldehydes, alkanes, fatty acids, primary alcohol and cholesterol. The total wax load in MT mature fruits was reduced by 44.2 % compared with WT. Except for the minor wax components of primary alcohol and cholesterol, the amounts of all major wax fractions in MT mature fruits were decreased in varying degrees. The major reduction occurred in aldehydes that decreased 96.4 % and alkanes that decreased 81.9 %, which was consistent with scanning electron micrographs of MT mature fruit surfaces that showed a severe loss of wax crystals. Hence, aldehydes and alkanes were suggested to be required for wax crystal formation in 'Newhall' navel orange fruits.

Carotenoid accumulation in postharvest “Cara Cara” navel orange (Citrus sinensis Osbeck) fruits stored at different temperatures was transcriptionally regulated in a tissue-dependent manner

The main objective of this work was to investigate the effect of storage temperature (4 and 20 °C) on carotenoid accumulation and on the expression levels of seven carotenoid biosynthetic genes (Psy, Pds, Zds, Lcyb, Lcye, Hyb and Zep) in postharvest 'Cara Cara' navel orange (C. sinensis Osbeck) fruits. Storage at 20 °C rapidly increased the carotenoid content in the peel, whereas the content remained unchanged in the pulp before 35 days of storage. By contrast, storage at 4 °C maintained the carotenoid content in the peel before 35 days of storage, after which it slightly increased as time progressed. However, the content in the pulp gradually increased over the entire storage period. In the peel, the gene expressions of Psy and Lcyb were up-regulated at 20 °C but remained unchanged at 4 °C. In addition, the gene expressions of Zds, Hyb, and Zep were repressed at both temperatures before the early storage, followed by a rapid increase only at 20 °C. Then the expressions remained constant level at both temperatures, with the expression level at 20 °C higher than that at 4 °C. Low temperature (4 °C) apparently induced the expression of all the test carotenoid biosynthetic genes in the pulp, in contrast to the nearly stable level at 20 °C. Our present study suggests that the carotenoid biosynthesis in postharvest 'Cara Cara' fruits is transcriptionally regulated, and storage temperature affects the carotenoid accumulation and gene expression in a tissue-dependent manner. Temperature could affect the carotenoid biosynthesis in postharvest 'Cara Cara' fruits in a tissue-dependent manner. The carotenoid biosynthesis in postharvest 'Cara Cara' fruits was transcriptionally regulated by correlated genes.

Effects of foliar application with compost tea and filtrate biogas slurry liquid on yield and fruit quality of Washington navel orange (Citrus sinenesis Osbeck) trees

Sixteen-year-old navel orange trees at a private orchard located in Kafer El-Sheikh Governorate, Egypt, were used in this study. Compost tea (CT) and filtrate biogas slurry liquid (FLB) were applied at two different concentrations (50% and 100%); control trees were sprayed with water. Trees treated with CT at 100% were the highest in yield, fruit weight, and vitamin C, whereas the highest percentage of fruit set, fruit number, and soluble solid content (SSC), lowest fruit drop, and highest reducing and total sugars were in trees treated with 100% FLB. Concentrations at 50% for both foliar application (CT and FLB) improved yield and fruit characteristics than control treatment. Generally, using a foliar application of compost tea and filtrate biogas slurry liquid at (100%) treatments as food nutrients could be recommended to improve the yield and fruit quality of navel orange fruits under the current study conditions. Implications: Consequently from the previously mentioned results, it was clear the great role of compost tea (CT) and filtrate biogas slurry liquid (FLB) as two sources of foliar application of organic fertilization for Washington navel orange grown in a clay loamy soil, as they are indispensable for improvement of the nutritional status of the navel orange trees and production of maximum yield and quality of orange, as well as minimizing the cost of production and in turn increasing the income of orange orchard. So, it should be recommended the superiority of application of FLB and CT, especially 100%, which gave the best results in yield and physical and chemical characteristics of navel orange fruits.

Effect of Balanced Fertilization and Fertilizer Levels on Navel Orange Yield and Fruit Quality

Effect of Balanced Fertilization and Fertilizer Levels on Navel Orange Yield and Fruit Quality

Effect of a New Chemical Formula on Postharvest Decay Incidence in Citrus Fruit

Postharvest diseases caused by Geotricum candidum (sour rot), Penicillium digitatum (green mould), and P. italicum (blue mould) are the most important negative factors affecting handling and marketing of citrus fruits in Egypt. A new formula containing stevia leaf powder and a mixture of the three commercial chemical active ingredients: ketoconazole, fluconazole, and itraconazole has been successfully applied. Either chitosan or water wax were used as carriers, against fruit mould pathogenic fungi under laboratory and storage conditions. Results of the in vitro test showed that a complete reduction in linear fugal growth was observed when the ingredients of the new formula were used individually at a concentration of 400 μg/ml each, while a mixture of all the tested chemicals had a superior effect with all fungal growth completely inhibited with the use of the mixture at a concentration of 100 μg/ml. Similar results were recorded on citrus fruits which were coated with the suggested formula of chitosan or wax containing chemical com- pounds as a semi applicable technique using navel orange peel discs. Furthermore, the obtained results were confirmed using in vivo testing on navel orange and lime fruits, under artificial inoculation conditions of the pathogenic fungi within a storage period extend- ed for four weeks. The proposed approach provides the treated agricultural products with long acting protection against microbial invasion and even association. This formula could be used as a fungicide alternative for protecting the agricultural products which have high moisture contents. The formula can be used against mould pathogens to prolong the healthy shelf life of the agricultural products. Such a treatment is safe, cheap, easily applied, and without residues which are harmful to people and the environment.

Early Navel Orange Fruit Yield, Quality, and Maturity in Response to Late-season Water Stress

The objective of this study was to measure effects of late-season water stress on fruit yield, size, quality, and color of an early-maturing navel orange cultivar, Citrus sinensis (L.) Osbeck ‘Beck-Earli’. Three irrigation regimes were initiated in August in the southern San Joaquin Valley of California in 2006, 2007, and 2008. Increasing levels of water stress resulted in decreasing midday shaded leaf water potential (SLWP) ranging from –1.4 MPa in early September to a minimum of –2.5 MPa at harvest. Generally, over the course of the 3 years, late-season water stress decreased fruit grade and increased soluble solids concentration (SSC), titratable acidity (TA), the BrimA index, and orange color. Fruit juiciness and SSC:TA ratios were unaffected by late-season water stress. The intensity of the water stress in 2007 decreased fruit yield by number and weight and decreased the percentage of large fruit. When trees exposed to 2 years of late-season water stress were fully irrigated the next year, fruit yield and quality were similar to trees that had not experienced late-season water stress for the 3 years of the study.

Induction of disease resistance and ROS metabolism in navel oranges by chitosan

The objective of this work was to evaluate how disease resistance and reactive oxygen species (ROS) metabolism in harvested navel oranges ( Citrus sinensis L. Osbeck) may be affected by chitosan. Fresh navel oranges were treated with 2% chitosan or 0.5% glacial acetic acid (control) solution for 1 min, and some were inoculated with Penicillium italicum and Penicillium digitatum. Then, the fruit were stored at 20 °C and 85–95% RH. Treatment with 2% chitosan significantly reduced the disease incidence and the lesion diameter compared with control fruit. This treatment effectively enhanced the activities of peroxidase (POD) and superoxide dismutase (SOD), and levels of glutathione (GSH) and hydrogen peroxide (H 2O 2), inhibited the activities of catalase (CAT) and the decreases of ascorbate (AsA) content during navel orange fruits storage. Ascorbate peroxidase (APX) activity in the navel orange fruit was induced slightly by the chitosan treatment during 14–21 days storage. However, glutathione reductase (GR) activity in the fruit was not enhanced by the chitosan treatment. These results indicated that chitosan treatment could induce the navel orange fruit disease resistance by regulating the H 2O 2 levels, antioxidant enzyme and ascorbate–glutathione cycle.

Laser diagnostic technology for early detection of pathogen infestation in orange fruits

Due to an increased expectation of food products that respect high quality and safety standards, there is a need for the growth of accurate, fast, objective and non-destructive technologies for quality determination of food and agricultural products. For this purpose, a diagnostic system based on laser photoacoustic spectroscopy (LPAS) was developed at ENEA Frascati Molecular Spectroscopy Laboratory (Italy). In the design of the photoacoustic detector, particular emphasis was placed in attaining a high sensitivity in detecting ethylene (ET) down to sub-parts per billion level (minimum detectable concentration 0.2 ppb). This was required due to the necessity to monitor and follow up ET production at a single fruit scale. ET is normally synthesised in very low amounts by healthy citrus fruits; however stress conditions such as pathogen attack may induce a substantial increase in the synthesised ET. In the present paper, the comparison between the ET emitted by healthy oranges ( Citrus sinensis L. Osbeck) cv Navel and by Phytophthora citrophthora infested Navel orange fruits are reported. The obtained results show a well evident increase in ET emission from the infested fruit with respect to the healthy one, even 24 h after the inoculation with the pathogen; at that time the tissue necrosis was not yet visible, and the fruit was also not yet damaged. The possibility to perform a real time non-destructive detection of ET traces makes the LPAS a powerful tool for monitoring the healthy state of the citrus fruits.

Nondestructive measurement of soluble solid content of navel orange fruit by visible–NIR spectrometric technique with PLSR and PCA-BPNN

A relationship was established between the soluble solid content (SSC) of navel orange fruit determined by destructive measurement and visible–near infrared diffuse reflectance spectra in the wavelength range of 350–1800 nm. Multiplicative scatter correction (MSC) and standard normal variate correction (SNV) were applied to the spectra, partial least squares regression (PLSR) and back propagation neural network (BPNN) based on principal component analysis (PCA) were used to develop the models for predicting the SSC of intact navel orange fruit. Thirty-eight unknown samples were used to evaluate the performance of these models. The principal component analysis-back propagation (PCA-BPNN) method with MSC spectral pretreatment obtain the best predictive results, resulting in correlation coefficient, root mean square error of prediction (RMSEP), average difference between predicted and measured values (Bias) of 0.90, 0.68 °Brix and 0.16 °Brix, respectively. Experimental results indicate that PCA-BPNN is a suitable tool to model the non-linear complex system, with additional advantages over PLSR, and the vis/NIR spectrometric technique can be used for measuring the SSC of intact navel orange fruit, nondestructively.

Expression of a senescence-associated cysteine protease gene related to peel pitting of navel orange (Citrus sinensis L. Osbeck)

Previously, a suppression subtractive hybridization library was constructed to identify differentially expressed genes in peel pitting of navel orange fruit and a cDNA fragment sharing high similarities to cysteine protease genes was identified. In this study, we cloned its full-length cDNA sequence, designated CsCP, using the Rapid amplification of cDNA ends approach. It consists of 1,409 nucleotides and its ORF encodes 361 amino acids predicted to have an N-terminal signal peptide. Phylogenetic analysis revealed that CsCP belonged to the aleurain group in papain family of cysteine proteases. According to quantitative RT-PCR, the expression of CsCP was enhanced during the development of postharvest peel pitting concomitant with senescence, although it was detectable in all tested tissues including root, leaf, flower and peel of fruit. RNA gel blot analysis showed that the CsCP expression was induced by hypoxia (3% O2), but repressed by anoxia (0% O2), wounding, ethylene and high temperature (40°C). Conclusively, the CsCP is a senescence-associated gene and up-regulated during the development of citrus postharvest peel pitting, which provides a basis to understand its role in citrus peel pitting.